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Ludington AJ, Hammond JM, Breen J, Deveson IW, Sanders KL. New chromosome-scale genomes provide insights into marine adaptations of sea snakes (Hydrophis: Elapidae). BMC Biol 2023; 21:284. [PMID: 38066641 PMCID: PMC10709897 DOI: 10.1186/s12915-023-01772-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 11/20/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND Sea snakes underwent a complete transition from land to sea within the last ~ 15 million years, yet they remain a conspicuous gap in molecular studies of marine adaptation in vertebrates. RESULTS Here, we generate four new annotated sea snake genomes, three of these at chromosome-scale (Hydrophis major, H. ornatus and H. curtus), and perform detailed comparative genomic analyses of sea snakes and their closest terrestrial relatives. Phylogenomic analyses highlight the possibility of near-simultaneous speciation at the root of Hydrophis, and synteny maps show intra-chromosomal variations that will be important targets for future adaptation and speciation genomic studies of this system. We then used a strict screen for positive selection in sea snakes (against a background of seven terrestrial snake genomes) to identify genes over-represented in hypoxia adaptation, sensory perception, immune response and morphological development. CONCLUSIONS We provide the best reference genomes currently available for the prolific and medically important elapid snake radiation. Our analyses highlight the phylogenetic complexity and conserved genome structure within Hydrophis. Positively selected marine-associated genes provide promising candidates for future, functional studies linking genetic signatures to the marine phenotypes of sea snakes and other vertebrates.
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Affiliation(s)
- Alastair J Ludington
- School of Biological Sciences, The University of Adelaide, Adelaide, SA, 5005, Australia.
| | - Jillian M Hammond
- Genomics and Inherited Disease Program, Garvan Institute of Medical Research, Sydney, NSW, Australia
- Centre for Population Genomics, Garvan Institute of Medical Research and Murdoch Children's Research Institute, Darlinghurst, Australia
| | - James Breen
- Indigenous Genomics, Telethon Kids Institute, Adelaide, Australia
- John Curtin School of Medical Research, College of Health & Medicine, Australian National University, Canberra, Australia
| | - Ira W Deveson
- Genomics and Inherited Disease Program, Garvan Institute of Medical Research, Sydney, NSW, Australia
- Centre for Population Genomics, Garvan Institute of Medical Research and Murdoch Children's Research Institute, Darlinghurst, Australia
- Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Kate L Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, SA, 5005, Australia.
- The South Australian Museum, Adelaide, Australia.
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2
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Rossetto IH, Sanders KL, Simões BF, Van Cao N, Ludington AJ. Functional Duplication of the Short-Wavelength-Sensitive Opsin in Sea Snakes: Evidence for Reexpanded Color Sensitivity Following Ancestral Regression. Genome Biol Evol 2023; 15:evad107. [PMID: 37434309 DOI: 10.1093/gbe/evad107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/07/2023] [Indexed: 07/13/2023] Open
Abstract
Color vision is mediated by ancient and spectrally distinct cone opsins. Yet, while there have been multiple losses of opsin genes during the evolution of tetrapods, evidence for opsin gains via functional duplication is extremely scarce. Previous studies have shown that some secondarily marine elapid snakes have acquired expanded "UV-blue" sensitivity via changes at key spectral tuning amino acid sites of the Short-Wavelength Opsin 1 (SWS1) gene. Here, we use elapid reference genomes to show that the molecular origin of this adaptation involved repeated, proximal duplications of the SWS1 gene in the fully marine Hydrophis cyanocinctus. This species possesses four intact SWS1 genes; two of these genes have the ancestral UV sensitivity, and two have a derived sensitivity to the longer wavelengths that dominate marine habitats. We suggest that this remarkable expansion of the opsin repertoire of sea snakes functionally compensates for the ancestral losses of two middle-wavelength opsins in the earliest (dim-light adapted) snakes. This provides a striking contrast to the evolution of opsins during ecological transitions in mammals. Like snakes, early mammals lost two cone photopigments; however, lineages such as bats and cetaceans underwent further opsin losses during their adaptation to dim-light environments.
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Affiliation(s)
- Isaac H Rossetto
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
| | - Kate L Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
| | - Bruno F Simões
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
- School of Biological and Marine Sciences, University of Plymouth, Plymouth, Devon, United Kingdom
| | - Nguyen Van Cao
- Department of Aquaculture Biotechnology, Institute of Oceanography, Vietnamese Academy of Science and Technology, Nha Trang, Khánh Hòa, Vietnam
| | - Alastair J Ludington
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
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3
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Folwell MJ, Sanders KL, Brennan PLR, Crowe-Riddell JM. First evidence of hemiclitores in snakes. Proc Biol Sci 2022; 289:20221702. [PMID: 36515117 PMCID: PMC9748774 DOI: 10.1098/rspb.2022.1702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Female genitalia are conspicuously overlooked in comparison to their male counterparts, limiting our understanding of sexual reproduction across vertebrate lineages. This study is the first complete description of the clitoris (hemiclitores) in female snakes. We describe morphological variation in size and shape (n = 9 species, 4 families) that is potentially comparable to the male intromittent organs in squamate reptiles (hemipenes). Dissection, diffusible iodine contrast-enhanced micro-CT and histology revealed that, unlike lizard hemiclitores, the snake hemiclitores are non-eversible structures. The two individual hemiclitores are separated medially by connective tissue, forming a triangular structure that extends posteriorly. Histology of the hemiclitores in Australian death adders (Acanthophis antarcticus) showed erectile tissue and strands/bundles of nerves, but no spines (as is found in male hemipenes). These histological features suggest the snake hemiclitores have functional significance in mating and definitively show that the hemiclitores are not underdeveloped hemipenes or scent glands, which have been erroneously indicated in other studies. Our discovery supports that hemiclitores have been retained across squamates and provides preliminary evidence of differences in this structure among snake species, which can be used to further understand systematics, reproductive evolution and ecology across squamate reptiles.
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Affiliation(s)
- Megan J. Folwell
- School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Kate L. Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
| | | | - Jenna M. Crowe-Riddell
- School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia,School of Agriculture, Biomedicine and Environment, La Trobe University, VIC 3086, Australia,Museum of Zoology, University of Michigan, Ann Arbor, MI 48108, USA,Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA
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4
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Sherratt E, Nash-Hahn T, Nankivell JH, Rasmussen AR, Hampton PM, Sanders KL. Macroevolution in axial morphospace: innovations accompanying the transition to marine environments in elapid snakes. R Soc Open Sci 2022; 9:221087. [PMID: 36569233 PMCID: PMC9768463 DOI: 10.1098/rsos.221087] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 11/29/2022] [Indexed: 06/17/2023]
Abstract
Sea snakes in the Hydrophis-Microcephalophis clade (Elapidae) show exceptional body shape variation along a continuum from similar forebody and hindbody girths, to dramatically reduced girths of the forebody relative to hindbody. The latter is associated with specializations on burrowing prey. This variation underpins high sympatric diversity and species richness and is not shared by other marine (or terrestrial) snakes. Here, we examined a hypothesis that macroevolutionary changes in axial development contribute to the propensity, at clade level, for body shape change. We quantified variation in the number and size of vertebrae in two body regions (pre- and post-apex of the heart) for approximately 94 terrestrial and marine elapids. We found Hydrophis-Microcephalophis exhibit increased rates of vertebral evolution in the pre- versus post-apex regions compared to all other Australasian elapids. Unlike other marine and terrestrial elapids, axial elongation in Hydrophis-Microcephalophis occurs via the preferential addition of vertebrae pre-heart apex, which is the region that undergoes concomitant shifts in vertebral number and size during transitions along the relative fore- to hindbody girth axis. We suggest that this macroevolutionary developmental change has potentially acted as a key innovation in Hydrophis-Microcephalophis by facilitating novel (especially burrowing) prey specializations that are not shared with other marine snakes.
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Affiliation(s)
- Emma Sherratt
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
| | - Tamika Nash-Hahn
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - James H. Nankivell
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
| | - Arne R. Rasmussen
- The Royal Danish Academy, Institute of Conservation, 1435 Copenhagen, Denmark
| | - Paul M. Hampton
- Department of Biology, Colorado Mesa University, Grand Junction, CO 81501, USA
| | - Kate L. Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
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5
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Cox N, Young BE, Bowles P, Fernandez M, Marin J, Rapacciuolo G, Böhm M, Brooks TM, Hedges SB, Hilton-Taylor C, Hoffmann M, Jenkins RKB, Tognelli MF, Alexander GJ, Allison A, Ananjeva NB, Auliya M, Avila LJ, Chapple DG, Cisneros-Heredia DF, Cogger HG, Colli GR, de Silva A, Eisemberg CC, Els J, Fong G A, Grant TD, Hitchmough RA, Iskandar DT, Kidera N, Martins M, Meiri S, Mitchell NJ, Molur S, Nogueira CDC, Ortiz JC, Penner J, Rhodin AGJ, Rivas GA, Rödel MO, Roll U, Sanders KL, Santos-Barrera G, Shea GM, Spawls S, Stuart BL, Tolley KA, Trape JF, Vidal MA, Wagner P, Wallace BP, Xie Y. A global reptile assessment highlights shared conservation needs of tetrapods. Nature 2022; 605:285-290. [PMID: 35477765 PMCID: PMC9095493 DOI: 10.1038/s41586-022-04664-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 03/16/2022] [Indexed: 11/29/2022]
Abstract
Comprehensive assessments of species’ extinction risks have documented the extinction crisis1 and underpinned strategies for reducing those risks2. Global assessments reveal that, among tetrapods, 40.7% of amphibians, 25.4% of mammals and 13.6% of birds are threatened with extinction3. Because global assessments have been lacking, reptiles have been omitted from conservation-prioritization analyses that encompass other tetrapods4–7. Reptiles are unusually diverse in arid regions, suggesting that they may have different conservation needs6. Here we provide a comprehensive extinction-risk assessment of reptiles and show that at least 1,829 out of 10,196 species (21.1%) are threatened—confirming a previous extrapolation8 and representing 15.6 billion years of phylogenetic diversity. Reptiles are threatened by the same major factors that threaten other tetrapods—agriculture, logging, urban development and invasive species—although the threat posed by climate change remains uncertain. Reptiles inhabiting forests, where these threats are strongest, are more threatened than those in arid habitats, contrary to our prediction. Birds, mammals and amphibians are unexpectedly good surrogates for the conservation of reptiles, although threatened reptiles with the smallest ranges tend to be isolated from other threatened tetrapods. Although some reptiles—including most species of crocodiles and turtles—require urgent, targeted action to prevent extinctions, efforts to protect other tetrapods, such as habitat preservation and control of trade and invasive species, will probably also benefit many reptiles. An extinction-risk assessment of reptiles shows that at least 21.1% of species are threatened by factors such as agriculture, logging, urban development and invasive species, and that efforts to protect birds, mammals and amphibians probably also benefit many reptiles.
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Affiliation(s)
- Neil Cox
- Biodiversity Assessment Unit, IUCN-Conservation International, Washington, DC, USA
| | | | - Philip Bowles
- Biodiversity Assessment Unit, IUCN-Conservation International, Washington, DC, USA
| | - Miguel Fernandez
- NatureServe, Arlington, VA, USA.,Smithsonian-Mason School of Conservation and Department of Environmental Science and Policy, George Mason University, Fairfax, VA, USA.,Instituto de Ecología, Universidad Mayor de San Andrés, La Paz, Bolivia
| | - Julie Marin
- Université Sorbonne Paris Nord, INSERM, IAME, Bobigny, France
| | - Giovanni Rapacciuolo
- Institute for Biodiversity Science and Sustainability, California Academy of Sciences, San Francisco, CA, USA
| | - Monika Böhm
- Institute of Zoology, Zoological Society of London, London, UK
| | - Thomas M Brooks
- IUCN, Gland, Switzerland.,World Agroforestry Center (ICRAF), University of The Philippines, Los Baños, The Philippines.,Institute for Marine & Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
| | - S Blair Hedges
- Center for Biodiversity, Temple University, Philadelphia, PA, USA
| | - Craig Hilton-Taylor
- Science & Data Centre: Biodiversity Assessment & Knowledge Team, IUCN, Cambridge, UK
| | - Michael Hoffmann
- Conservation and Policy, Zoological Society of London, London, UK
| | - Richard K B Jenkins
- Science & Data Centre: Biodiversity Assessment & Knowledge Team, IUCN, Cambridge, UK
| | - Marcelo F Tognelli
- Biodiversity Assessment Unit, IUCN-Conservation International, Washington, DC, USA
| | - Graham J Alexander
- Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | | | - Natalia B Ananjeva
- Department of Herpetology, Zoological Institute, St Petersburg, Russian Federation
| | - Mark Auliya
- Department of Herpetology, Leibniz Institute for the Analysis of Biodiversity Change, Zoological Research Museum Alexander Koenig, Bonn, Germany
| | - Luciano Javier Avila
- Grupo Herpetología Patagónica (GHP-LASIBIBE), Instituto Patagónico para el Estudio de los Ecosistemas Continentales (IPEEC-CONICET), Puerto Madryn, Argentina
| | - David G Chapple
- School of Biological Sciences, Monash University, Clayton, Victoria, Australia
| | - Diego F Cisneros-Heredia
- Colegio de Ciencias Biológicas y Ambientales, Museo de Zoología, Instituto de Biodiversidad Tropical iBIOTROP, Universidad San Francisco de Quito USFQ, Quito, Ecuador.,Instituto Nacional de Biodiversidad, Quito, Ecuador
| | - Harold G Cogger
- Australian Museum Research Institute, Sydney, New South Wales, Australia
| | - Guarino R Colli
- Departamento de Zoologia, Universidade de Brasília, Brasília, Brazil
| | - Anslem de Silva
- South Asia Regional Office, Crocodile Specialist Group, Gampols, Sri Lanka
| | | | - Johannes Els
- Environment and Protected Areas Authority, Government of Sharjah, Sharjah, United Arab Emirates
| | - Ansel Fong G
- Centro Oriental de Ecosistemas y Biodiversidad (BIOECO), Museo de Historia Natural "Tomás Romay", Santiago de Cuba, Cuba
| | - Tandora D Grant
- Conservation Science & Wildlife Health, San Diego Zoo Wildlife Alliance, San Diego, CA, USA
| | | | | | - Noriko Kidera
- Department of Biosphere-Geosphere Science, Okayama University of Science, Okayama, Japan.,National Institute for Environmental Studies, Tsukuba, Japan
| | - Marcio Martins
- Departamento de Ecologia, Universidade de São Paulo, São Paulo, Brazil
| | - Shai Meiri
- School of Zoology & the Steinhardt Museum of Natural History, Tel Aviv University, Tel Aviv, Israel
| | - Nicola J Mitchell
- School of Biological Sciences, The University of Western Australia, Crawley, Western Australia, Australia
| | | | | | - Juan Carlos Ortiz
- Departamento de Zoología, Universidad de Concepción, Concepción, Chile
| | - Johannes Penner
- Chair of Wildlife Ecology and Management, University of Freiburg, Freiburg, Germany.,Museum für Naturkunde - Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
| | | | - Gilson A Rivas
- Museo de Biología, Universidad del Zulia, Maracaibo, Venezuela
| | - Mark-Oliver Rödel
- Museum für Naturkunde - Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
| | - Uri Roll
- Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel
| | - Kate L Sanders
- University of Adelaide, Adelaide, South Australia, Australia
| | | | - Glenn M Shea
- Australian Museum Research Institute, Sydney, New South Wales, Australia.,Sydney School of Veterinary Science B01, University of Sydney, Sydney, New South Wales, Australia
| | | | - Bryan L Stuart
- Section of Research & Collections, North Carolina Museum of Natural Sciences, Raleigh, NC, USA
| | - Krystal A Tolley
- Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa.,South African National Biodiversity Institute, Cape Town, South Africa
| | | | - Marcela A Vidal
- Departamento de Ciencias Básicas, Facultad de Ciencias, Universidad del Bío-Bío, Chillán, Chile
| | | | | | - Yan Xie
- Chinese Academy of Sciences, Beijing, China
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6
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Galbraith JD, Ludington AJ, Sanders KL, Amos TG, Thomson VA, Enosi Tuipulotu D, Dunstan N, Edwards RJ, Suh A, Adelson DL. Horizontal Transposon Transfer and Its Implications for the Ancestral Ecology of Hydrophiine Snakes. Genes (Basel) 2022; 13:genes13020217. [PMID: 35205262 PMCID: PMC8872380 DOI: 10.3390/genes13020217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 01/23/2022] [Accepted: 01/23/2022] [Indexed: 02/04/2023] Open
Abstract
Transposable elements (TEs), also known as jumping genes, are sequences able to move or copy themselves within a genome. As TEs move throughout genomes they often act as a source of genetic novelty, hence understanding TE evolution within lineages may help in understanding environmental adaptation. Studies into the TE content of lineages of mammals such as bats have uncovered horizontal transposon transfer (HTT) into these lineages, with squamates often also containing the same TEs. Despite the repeated finding of HTT into squamates, little comparative research has examined the evolution of TEs within squamates. Here we examine a diverse family of Australo-Melanesian snakes (Hydrophiinae) to examine if the previously identified, order-wide pattern of variable TE content and activity holds true on a smaller scale. Hydrophiinae diverged from Asian elapids ~30 Mya and have since rapidly diversified into six amphibious, ~60 marine and ~100 terrestrial species that fill a broad range of ecological niches. We find TE diversity and expansion differs between hydrophiines and their Asian relatives and identify multiple HTTs into Hydrophiinae, including three likely transferred into the ancestral hydrophiine from fish. These HTT events provide the first tangible evidence that Hydrophiinae reached Australia from Asia via a marine route.
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Affiliation(s)
- James D. Galbraith
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia; (J.D.G.); (A.J.L.); (K.L.S.); (V.A.T.)
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK
| | - Alastair J. Ludington
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia; (J.D.G.); (A.J.L.); (K.L.S.); (V.A.T.)
| | - Kate L. Sanders
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia; (J.D.G.); (A.J.L.); (K.L.S.); (V.A.T.)
| | - Timothy G. Amos
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia; (T.G.A.); (D.E.T.)
- Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - Vicki A. Thomson
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia; (J.D.G.); (A.J.L.); (K.L.S.); (V.A.T.)
| | - Daniel Enosi Tuipulotu
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia; (T.G.A.); (D.E.T.)
- Division of Immunity, Inflammation and Infection, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT 2601, Australia
| | | | - Richard J. Edwards
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia; (T.G.A.); (D.E.T.)
- Correspondence: (R.J.E.); (A.S.); (D.L.A.)
| | - Alexander Suh
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TU, UK
- Department of Organismal Biology-Systematic Biology, Evolutionary Biology Centre, Uppsala University, SE-752 36 Uppsala, Sweden
- Correspondence: (R.J.E.); (A.S.); (D.L.A.)
| | - David L. Adelson
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia; (J.D.G.); (A.J.L.); (K.L.S.); (V.A.T.)
- South Australian Museum, Adelaide, SA 5000, Australia
- Correspondence: (R.J.E.); (A.S.); (D.L.A.)
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7
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Gower DJ, Fleming JF, Pisani D, Vonk FJ, Kerkkamp HMI, Peichl L, Meimann S, Casewell NR, Henkel CV, Richardson MK, Sanders KL, Simões BF. Eye-Transcriptome and Genome-Wide Sequencing for Scolecophidia: Implications for Inferring the Visual System of the Ancestral Snake. Genome Biol Evol 2021; 13:6430116. [PMID: 34791190 PMCID: PMC8643396 DOI: 10.1093/gbe/evab253] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2021] [Indexed: 12/28/2022] Open
Abstract
Molecular genetic data have recently been incorporated in attempts to reconstruct the ecology of the ancestral snake, though this has been limited by a paucity of data for one of the two main extant snake taxa, the highly fossorial Scolecophidia. Here we present and analyze vision genes from the first eye-transcriptomic and genome-wide data for Scolecophidia, for Anilios bicolor, and A. bituberculatus, respectively. We also present immunohistochemistry data for retinal anatomy and visual opsin-gene expression in Anilios. Analyzed in the context of 19 lepidosaurian genomes and 12 eye transcriptomes, the new genome-wide and transcriptomic data provide evidence for a much more reduced visual system in Anilios than in non-scolecophidian (=alethinophidian) snakes and in lizards. In Anilios, there is no evidence of the presence of 7 of the 12 genes associated with alethinophidian photopic (cone) phototransduction. This indicates extensive gene loss and many of these candidate gene losses occur also in highly fossorial mammals with reduced vision. Although recent phylogenetic studies have found evidence for scolecophidian paraphyly, the loss in Anilios of visual genes that are present in alethinophidians implies that the ancestral snake had a better-developed visual system than is known for any extant scolecophidian.
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Affiliation(s)
- David J Gower
- Life Sciences, The Natural History Museum, London, United Kingdom
| | - James F Fleming
- School of Life Sciences, University of Bristol, Bristol, United Kingdom.,Institute for Advanced Biosciences, Keio University, Yamagata, Japan
| | - Davide Pisani
- School of Life Sciences, University of Bristol, Bristol, United Kingdom.,School of Earth Sciences, University of Bristol, Bristol, United Kingdom
| | - Freek J Vonk
- Naturalis Biodiversity Center, Leiden, The Netherlands
| | | | - Leo Peichl
- Institute of Cellular and Molecular Anatomy, Dr. Senckenberg Anatomy, Goethe University Frankfurt, Frankfurt am Main, Germany.,Institute of Clinical Neuroanatomy, Dr. Senckenberg Anatomy, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Sonja Meimann
- Institute of Cellular and Molecular Anatomy, Dr. Senckenberg Anatomy, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Nicholas R Casewell
- Centre for Snakebite Research & Interventions, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Christiaan V Henkel
- Institute of Biology, University of Leiden, Leiden, The Netherlands.,Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
| | | | - Kate L Sanders
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Bruno F Simões
- School of Life Sciences, University of Bristol, Bristol, United Kingdom.,School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia.,School of Biological and Marine Sciences, University of Plymouth, Plymouth, United Kingdom
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8
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Weinstein SA, Sanders KL, White J. Construction of Accurate Medical Risk Profiles for Venomous Snakes Requires Correct Identification of the Envenoming Species. Am J Forensic Med Pathol 2021; 42:407-408. [PMID: 34793411 DOI: 10.1097/paf.0000000000000725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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9
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García-Cobos D, Gómez-Sánchez DA, Crowe-Riddell JM, Sanders KL, Molina J. Ecological and sexual roles of scale mechanoreceptors in two species of Neotropical freshwater snake (Dipsadinae: Helicops). Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blab129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Understanding the roles of ecological and sexual selection in the variation of sensory systems may elucidate aspects of the natural history of organisms. Little is known about the evolution of mechanoreception in snakes and how the function and structure of mechanoreceptors vary between species or sexes. Here, we describe the internal and external morphology of cephalic mechanoreceptor sensilla and quantify inter- and intraspecific variation in four sensilla traits of two freshwater snake species that differ in their habitat and diet preferences, Helicops pastazae and Helicops angulatus, by combining scanning electron microscopy (SEM), histological techniques and image analyses. SEM showed sensilla as prominent evaginations of the epidermis surrounded by concentric rings, with H. pastazae having larger and more heterogeneous sensilla. In both species, histology showed a reduction in the outer epidermal layer above the sensilla with a grouping of dermally derived central cells below it. Higher values of sensilla traits were found in H. pastazae, except for the chin-shields. We also found that males of both species had significantly higher values of sensilla traits on all of the scales examined. We hypothesize that the variation in both qualitative and quantitative traits in scale sensilla might be a consequence of differences in foraging and/or reproductive strategies between species and sexes.
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Affiliation(s)
- Daniela García-Cobos
- Subdirección de Investigaciones, Colecciones Biológicas, Instituto de Investigación de Recursos Biológicos Alexander von Humboldt, Claustro de San Agustín, Villa de Leyva, Boyacá, Colombia
- Museo de Historia Natural C.J. Marinkelle, Universidad de los Andes, Departamento de Ciencias Biológicas, Bogotá D.C., Colombia
| | - Diego A Gómez-Sánchez
- Reserva Natural Rey Zamuro – Matarredonda, San Martín de los Llanos, Dpto. Meta, Colombia
| | - Jenna M Crowe-Riddell
- Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48100, USA
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Kate L Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Jorge Molina
- Centro de Investigaciones en Microbiología y Parasitología Tropical (CIMPAT), Universidad de los Andes, Departamento de Ciencias Biológicas, Bogotá D.C., Colombia
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10
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Galbraith JD, Ludington AJ, Sanders KL, Suh A, Adelson DL. Horizontal transfer and subsequent explosive expansion of a DNA transposon in sea kraits ( Laticauda). Biol Lett 2021; 17:20210342. [PMID: 34464541 PMCID: PMC8437027 DOI: 10.1098/rsbl.2021.0342] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Transposable elements (TEs) are self-replicating genetic sequences and are often described as important ‘drivers of evolution’. This driving force is because TEs promote genomic novelty by enabling rearrangement, and through exaptation as coding and regulatory elements. However, most TE insertions potentially lead to neutral or harmful outcomes, therefore host genomes have evolved machinery to suppress TE expansion. Through horizontal transposon transfer (HTT) TEs can colonize new genomes, and since new hosts may not be able to regulate subsequent replication, these TEs may proliferate rapidly. Here, we describe HTT of the Harbinger-Snek DNA transposon into sea kraits (Laticauda), and its subsequent explosive expansion within Laticauda genomes. This HTT occurred following the divergence of Laticauda from terrestrial Australian elapids approximately 15–25 Mya. This has resulted in numerous insertions into introns and regulatory regions, with some insertions into exons which appear to have altered UTRs or added sequence to coding exons. Harbinger-Snek has rapidly expanded to make up 8–12% of Laticauda spp. genomes; this is the fastest known expansion of TEs in amniotes following HTT. Genomic changes caused by this rapid expansion may have contributed to adaptation to the amphibious-marine habitat.
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Affiliation(s)
- James D Galbraith
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Alastair J Ludington
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Kate L Sanders
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Alexander Suh
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TU, UK.,Department of Organismal Biology - Systematic Biology, Evolutionary Biology Centre, Uppsala University, Uppsala SE-752 36, Sweden
| | - David L Adelson
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
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11
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Crowe-Riddell JM, Jolly CJ, Goiran C, Sanders KL. The sex life aquatic: sexually dimorphic scale mechanoreceptors and tactile courtship in a sea snake Emydocephalus annulatus (Elapidae: Hydrophiinae). Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blab069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Evolutionary transitions from terrestrial to aquatic habitats involve major selective shifts in animal signalling systems. Entirely marine snakes face two challenges during underwater social interactions: (1) finding mates when pheromones are diffused by water currents; and, once a mate is located, (2) maintaining contact and co-ordinating mating when tactile cues are diminished by buoyancy force. We explore the potential tactile roles of scale protuberances in the mating of turtle-headed sea snakes [Emydocephalus annulatus (Hydrophiinae)] by investigating sexual dimorphism in museum specimens (N = 59). In addition to the previously noted rostral spine on the snout, we found that mature males have enlarged structures located on the chin (genial knobs) and near the cloaca (anal knobs). Ultrastructural data indicates that the rostral spine is comprised of thickened epidermal and dermal layers, similar to rugosities on the body, and likely provide stimulation to the female during prodding by the male. In contrast, the genial and anal knobs have dermally derived central cells indicative of enlarged scale mechanoreceptors (i.e. sensilla). We suggest that these mechanoreceptors are critical to mating success: genial knobs may help amorous males orient to the direction of female motion; whereas, and anal knobs likely give somatosensory feedback for cloacal alignment
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Affiliation(s)
- Jenna M Crowe-Riddell
- School of Biological Sciences, The University of Adelaide, Adelaide, SA, Australia
- Ecology and Evolutionary Biology, University of Michigan, Ann Arbor MI, USA
| | - Chris J Jolly
- School of BioSciences, University of Melbourne, Parkville, VIC, Australia
- Museum & Art Gallery of the Northern Territory, Darwin, NT, Australia
- Australian Museum Research Institute, Australian Museum, Sydney, NSW, Australia
| | - Claire Goiran
- LabEx Corail and ISEA, Université de La Nouvelle-Calédonie, BP R4, Nouméa Cedex, New Caledonia
| | - Kate L Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, SA, Australia
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12
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Crowe-Riddell JM, Dix S, Pieterman L, Nankivell JH, Ford M, Ludington AJ, Simões BF, Dunstan N, Partridge JC, Sanders KL, Allen L. From matte banded to glossy black: structures underlying colour change in the caudal lures of southern death adders (Acanthophis antarcticus, Reptilia: Elapidae). Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blaa218] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Many ambush-foraging snakes move their tails to entice prey within striking range (‘caudal luring’). During ontogeny, the conspicuous hues of caudal lures change to match the cryptic patterning of the body/head. This coincides with decreased luring behaviour and reflects the trade-off between prey acquisition and camouflage as the snake grows. Australo-Papuan death adders (Acanthophis, Elapidae) are unique in that both juveniles and adults use caudal luring, but ontogenetic colour change has not been investigated. We examined the spectral reflectance, microstructure and pigmentation of caudal skin in wild-sourced and captive bred Acanthophis antarcticus ranging in body size (snout-vent length 116–674 mm; mass 3–832 g; N = 33) to test whether colour properties change as snakes grow. We found that lure colour is distinct from the cryptic body skin across the life history, and changes from a matte banding pattern (grey/black) in neonates/juveniles, to uniform and glossy black with a yellow ventral stripe in larger snakes. These colour changes are caused by increases in dermal pigmentation and a transition to a smooth, interlocking epidermal microstructure. To understand the selection pressures that might be driving ontogenetic colour change in this species, further studies should test how different prey types respond to distinct lure morphologies.
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Affiliation(s)
- Jenna M Crowe-Riddell
- School of Biological Sciences, The University of Adelaide, Adelaide SA, Australia
- Ecology and Evolutionary Biology, University of Michigan, Ann Arbor MI, USA
- Ecology and Evolutionary Biology, University of Michigan, Ann Arbor MI, USA
| | - Stacey Dix
- School of Biological Sciences, The University of Adelaide, Adelaide SA, Australia
| | - Ludo Pieterman
- School of Biological Sciences, The University of Adelaide, Adelaide SA, Australia
| | - James H Nankivell
- School of Biological Sciences, The University of Adelaide, Adelaide SA, Australia
| | - Matthew Ford
- School of Biological Sciences, The University of Adelaide, Adelaide SA, Australia
| | - Alastair J Ludington
- School of Biological Sciences, The University of Adelaide, Adelaide SA, Australia
| | - Bruno F Simões
- School of Biological Sciences, The University of Adelaide, Adelaide SA, Australia
- School of Biological and Marine Sciences, University of Plymouth, Plymouth, UK
| | | | - Julian C Partridge
- School of Biological Sciences and Oceans Institute, University of Western Australia, Crawley WA, Australia
| | - Kate L Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide SA, Australia
| | - Luke Allen
- School of Biological Sciences, The University of Adelaide, Adelaide SA, Australia
- Venom Supplies, Tanunda, South Australia, Australia
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13
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Ludington AJ, Sanders KL. Demographic analyses of marine and terrestrial snakes (Elapidae) using whole genome sequences. Mol Ecol 2020; 30:545-554. [PMID: 33170980 DOI: 10.1111/mec.15726] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 10/13/2020] [Accepted: 11/03/2020] [Indexed: 11/27/2022]
Abstract
The question of whether spatial aspects of evolution differ in marine versus terrestrial realms has endured since Ernst Mayr's 1954 essay on marine speciation. Marine systems are often suggested to support larger and more highly connected populations, but quantitative comparisons with terrestrial systems have been lacking. Here, we compared the population histories of marine and terrestrial elapid snakes using the pairwise sequentially Markovian coalescent (PSMC) model to track historical fluctuations in species' effective population sizes (Ne ) from individual whole-genome sequences. To do this we generated a draft genome for the olive sea snake (Aiysurus laevis) and analysed this alongside six published elapid genomes and their sequence reads (marine species Hydrophis curtus, H. melanocephalus and Laticauda laticaudata; terrestrial species Pseudonaja textilis, Naja Naja and Notechis scutatus). Counter to the expectation that marine species should show higher overall Ne and less pronounced fluctuations in Ne , our analyses reveal demographic patterns that are highly variable among species and do not clearly correspond to major ecological divisions. At deeper time intervals, the four marine elapids appear to have experienced relatively stable Ne , while each terrestrial species shows a prominent upturn in Ne starting at ~4 million years ago (Ma) followed by an equally strong decline. However, over the last million years, all seven species show strong and divergent fluctuations. Estimates of Ne in the most recent intervals (~10 kya) are lowest in two of four marine species (H. melanocephalus and Laticauda), and do not correspond to contemporary range sizes in marine or terrestrial taxa.
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Affiliation(s)
- Alastair J Ludington
- School of Biological Science, The University of Adelaide, Adelaide, South Australia, Australia
| | - Kate L Sanders
- School of Biological Science, The University of Adelaide, Adelaide, South Australia, Australia
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14
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Galbraith JD, Ludington AJ, Suh A, Sanders KL, Adelson DL. New Environment, New Invaders-Repeated Horizontal Transfer of LINEs to Sea Snakes. Genome Biol Evol 2020; 12:2370-2383. [PMID: 33022046 PMCID: PMC7846101 DOI: 10.1093/gbe/evaa208] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2020] [Indexed: 12/12/2022] Open
Abstract
Although numerous studies have found horizontal transposon transfer (HTT) to be widespread across metazoans, few have focused on HTT in marine ecosystems. To investigate potential recent HTTs into marine species, we searched for novel repetitive elements in sea snakes, a group of elapids which transitioned to a marine habitat at most 18 Ma. Our analysis uncovered repeated HTTs into sea snakes following their marine transition. The seven subfamilies of horizontally transferred LINE retrotransposons we identified in the olive sea snake (Aipysurus laevis) are transcribed, and hence are likely still active and expanding across the genome. A search of 600 metazoan genomes found all seven were absent from other amniotes, including terrestrial elapids, with the most similar LINEs present in fish and marine invertebrates. The one exception was a similar LINE found in sea kraits, a lineage of amphibious elapids which independently transitioned to a marine environment 25 Ma. Our finding of repeated horizontal transfer events into marine snakes greatly expands past findings that the marine environment promotes the transfer of transposons. Transposons are drivers of evolution as sources of genomic sequence and hence genomic novelty. We identified 13 candidate genes for HTT-induced adaptive change based on internal or neighboring HTT LINE insertions. One of these, ADCY4, is of particular interest as a part of the KEGG adaptation pathway “Circadian Entrainment.” This provides evidence of the ecological interactions between species influencing evolution of metazoans not only through specific selection pressures, but also by contributing novel genomic material.
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Affiliation(s)
| | | | - Alexander Suh
- Department of Ecology and Genetics-Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Sweden.,Department of Organismal Biology-Systematic Biology, Evolutionary Biology Centre, Uppsala University, Sweden.,School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Kate L Sanders
- School of Biological Sciences, University of Adelaide, Australia
| | - David L Adelson
- School of Biological Sciences, University of Adelaide, Australia
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15
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Simões BF, Gower DJ, Rasmussen AR, Sarker MAR, Fry GC, Casewell NR, Harrison RA, Hart NS, Partridge JC, Hunt DM, Chang BS, Pisani D, Sanders KL. Spectral Diversification and Trans-Species Allelic Polymorphism during the Land-to-Sea Transition in Snakes. Curr Biol 2020; 30:2608-2615.e4. [PMID: 32470360 DOI: 10.1016/j.cub.2020.04.061] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Revised: 03/05/2020] [Accepted: 04/23/2020] [Indexed: 11/16/2022]
Abstract
Snakes are descended from highly visual lizards [1] but have limited (probably dichromatic) color vision attributed to a dim-light lifestyle of early snakes [2-4]. The living species of front-fanged elapids, however, are ecologically very diverse, with ∼300 terrestrial species (cobras, taipans, etc.) and ∼60 fully marine sea snakes, plus eight independently marine, amphibious sea kraits [1]. Here, we investigate the evolution of spectral sensitivity in elapids by analyzing their opsin genes (which are responsible for sensitivity to UV and visible light), retinal photoreceptors, and ocular lenses. We found that sea snakes underwent rapid adaptive diversification of their visual pigments when compared with their terrestrial and amphibious relatives. The three opsins present in snakes (SWS1, LWS, and RH1) have evolved under positive selection in elapids, and in sea snakes they have undergone multiple shifts in spectral sensitivity toward the longer wavelengths that dominate below the sea surface. Several relatively distantly related Hydrophis sea snakes are polymorphic for shortwave sensitive visual pigment encoded by alleles of SWS1. This spectral site polymorphism is expected to confer expanded "UV-blue" spectral sensitivity and is estimated to have persisted twice as long as the predicted survival time for selectively neutral nuclear alleles. We suggest that this polymorphism is adaptively maintained across Hydrophis species via balancing selection, similarly to the LWS polymorphism that confers allelic trichromacy in some primates. Diving sea snakes thus appear to share parallel mechanisms of color vision diversification with fruit-eating primates.
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Affiliation(s)
- Bruno F Simões
- University of Plymouth, School of Biological and Marine Sciences, Drake Circus, Plymouth PL4 8AA, United Kingdom; University of Bristol, School of Biological Sciences and School of Earth Sciences, Tyndall Avenue, Bristol BS8 1TG, United Kingdom; The University of Adelaide, School of Biological Sciences, North Terrace, Adelaide, South Australia 5005, Australia.
| | - David J Gower
- Department of Life Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom
| | - Arne R Rasmussen
- The Royal Danish Academy of Fine Arts, School of Architecture, Design and Conservation, Philip de Langes Allé, 1435 Copenhagen K, Denmark
| | - Mohammad A R Sarker
- University of Dhaka, Department of Zoology, Curzon Hall Campus, Dhaka 1000, Bangladesh
| | - Gary C Fry
- CSIRO Oceans and Atmosphere, Queensland Biosciences Precinct, St Lucia, Queensland 4072, Australia
| | - Nicholas R Casewell
- Liverpool School of Tropical Medicine, Centre for Snakebite Research & Interventions, Pembroke Place, Liverpool L3 5QA, United Kingdom
| | - Robert A Harrison
- Liverpool School of Tropical Medicine, Centre for Snakebite Research & Interventions, Pembroke Place, Liverpool L3 5QA, United Kingdom
| | - Nathan S Hart
- Macquarie University, Department of Biological Sciences, North Ryde, Sydney, New South Wales 2109, Australia
| | - Julian C Partridge
- The University of Western Australia, Oceans Institute, Crawley, Perth, Western Australia 6009, Australia
| | - David M Hunt
- The University of Western Australia, School of Biological Sciences, Crawley, Perth, Western Australia 6009, Australia; The Lions Eye Institute, Centre for Ophthalmology and Visual Science, Nedlands, Perth, Western Australia 6009, Australia
| | - Belinda S Chang
- University of Toronto, Departments of Ecology & Evolutionary, Cell & Systems Biology, Willcocks Street, Toronto M5S 3G5, Canada
| | - Davide Pisani
- University of Bristol, School of Biological Sciences and School of Earth Sciences, Tyndall Avenue, Bristol BS8 1TG, United Kingdom
| | - Kate L Sanders
- The University of Adelaide, School of Biological Sciences, North Terrace, Adelaide, South Australia 5005, Australia; Department of Life Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom
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16
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Nankivell JH, Goiran C, Hourston M, Shine R, Rasmussen AR, Thomson VA, Sanders KL. A new species of turtle-headed sea Snake (Emydocephalus: Elapidae) endemic to Western Australia. Zootaxa 2020; 4758:zootaxa.4758.1.6. [PMID: 32230158 DOI: 10.11646/zootaxa.4758.1.6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Indexed: 11/04/2022]
Abstract
We describe a new species of turtle-headed sea snake Emydocephalus orarius sp. nov. (Elapidae) from Western Australia's Coral Coast, Pilbara and Kimberley regions. Phylogenetic analysis of mitochondrial markers places the new species as the sister lineage to the two currently recognised species in Emydocephalus: E. annulatus from the Timor Sea reefs and Coral Sea, and E. ijimae from the Ryukyu Islands. Analysis of nuclear SNP data from the new species and E. annulatus from Australia and New Caledonia provides additional independent evidence of their evolutionary distinctiveness. The new taxon is usually morphologically diagnosable from its congeners using a combination of scalation and colour pattern characters, and appears to reach greater total lengths (>1 m in the new species versus typically ~80 cm in E. annulatus/E. ijimae). The new species is known largely from soft-bottomed trawl grounds, unlike E. annulatus and E.ijimae which usually inhabit coral reefs. The discovery of this new species brings the number of sea snake species endemic to Western Australia to six.
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Affiliation(s)
- James H Nankivell
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia.
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17
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Sherratt E, Sanders KL. Patterns of intracolumnar size variation inform the heterochronic mechanisms underlying extreme body shape divergence in microcephalic sea snakes. Evol Dev 2019; 22:283-290. [PMID: 31730744 DOI: 10.1111/ede.12328] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sea snakes (Hydrophiinae) that specialize on burrowing eel prey have repeatedly evolved tiny heads and reduced forebody relative to hindbody girths. Previous research has found that these "microcephalic" forms have higher counts of precaudal vertebrae, and postnatal ontogenetic changes cause their hindbodies to reach greater girths relative to their forebodies. We examine variation in vertebral size along the precaudal axis of neonates and adults of three species. In the nonmicrocephalic Hydrophis curtus, these intracolumnar patterns take the form of symmetrical curved profiles, with longer vertebrae in the midbody (50% of body length) relative to distal regions. In contrast, intracolumnar profiles in the microcephalic H. macdowelli and H. obscurus are strongly asymmetrical curves (negative skewness) due to the presence of numerous, smaller-sized vertebrate in the forebody (anterior to the heart). Neonate and adult H. macdowelli and H. obscurus specimens all exhibit this pattern, implying an onset of fore- versus hindbody decoupling in the embryo stage. Based on this, we suggest plausible developmental mechanisms involving the presence and positioning of Hox boundaries and heterochronic changes in segmentation. Tests of our hypotheses would give new insights into the drivers of rapid convergent shifts in evolution, but will ultimately require studies of gene expression in the embryos of relevant taxa.
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Affiliation(s)
- Emma Sherratt
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
| | - Kate L Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
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18
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Palci A, Seymour RS, Van Nguyen C, Hutchinson MN, Lee MSY, Sanders KL. Novel vascular plexus in the head of a sea snake (Elapidae, Hydrophiinae) revealed by high-resolution computed tomography and histology. R Soc Open Sci 2019; 6:191099. [PMID: 31598325 PMCID: PMC6774945 DOI: 10.1098/rsos.191099] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 08/01/2019] [Indexed: 05/03/2023]
Abstract
Novel phenotypes are often linked to major ecological transitions during evolution. Here, we describe for the first time an unusual network of large blood vessels in the head of the sea snake Hydrophis cyanocinctus. MicroCT imaging and histology reveal an intricate modified cephalic vascular network (MCVN) that underlies a broad area of skin between the snout and the roof of the head. It is mostly composed of large veins and sinuses and converges posterodorsally into a large vein (sometimes paired) that penetrates the skull through the parietal bone. Endocranially, this blood vessel leads into the dorsal cerebral sinus, and from there, a pair of large veins depart ventrally to enter the brain. We compare the condition observed in H. cyanocinctus with that of other elapids and discuss the possible functions of this unusual vascular network. Sea snakes have low oxygen partial pressure in their arterial blood that facilitates cutaneous respiration, potentially limiting the availability of oxygen to the brain. We conclude that this novel vascular structure draining directly to the brain is a further elaboration of the sea snakes' cutaneous respiratory anatomy, the most likely function of which is to provide the brain with an additional supply of oxygen.
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Affiliation(s)
- Alessandro Palci
- College of Science and Engineering, Flinders University, Adelaide, South Australia 5042, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
| | - Roger S. Seymour
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Cao Van Nguyen
- Institute of Oceanography, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | - Mark N. Hutchinson
- College of Science and Engineering, Flinders University, Adelaide, South Australia 5042, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
| | - Michael S. Y. Lee
- College of Science and Engineering, Flinders University, Adelaide, South Australia 5042, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
| | - Kate L. Sanders
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
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19
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Chapuis L, Kerr CC, Collin SP, Hart NS, Sanders KL. Underwater hearing in sea snakes (Hydrophiinae): first evidence of auditory evoked potential thresholds. ACTA ACUST UNITED AC 2019; 222:222/14/jeb198184. [PMID: 31345949 DOI: 10.1242/jeb.198184] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 07/01/2019] [Indexed: 11/20/2022]
Abstract
The viviparous sea snakes (Hydrophiinae) are a secondarily aquatic radiation of more than 60 species that possess many phenotypic adaptations to marine life. However, virtually nothing is known of the role and sensitivity of hearing in sea snakes. This study investigated the hearing sensitivity of the fully marine sea snake Hydrophis stokesii by measuring auditory evoked potential (AEP) audiograms for two individuals. AEPs were recorded from 40 Hz (the lowest frequency tested) up to 600 Hz, with a peak in sensitivity identified at 60 Hz (163.5 dB re. 1 µPa or 123 dB re. 1 µm s-2). Our data suggest that sea snakes are sensitive to low-frequency sounds but have relatively low sensitivity compared with bony fishes and marine turtles. Additional studies are required to understand the role of sound in sea snake life history and further assess these species' vulnerability to anthropogenic noise.
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Affiliation(s)
- Lucille Chapuis
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK .,Oceans Graduate School and the UWA Oceans Institute, The University of Western Australia, Perth, WA 6009, Australia
| | - Caroline C Kerr
- Oceans Graduate School and the UWA Oceans Institute, The University of Western Australia, Perth, WA 6009, Australia
| | - Shaun P Collin
- Oceans Graduate School and the UWA Oceans Institute, The University of Western Australia, Perth, WA 6009, Australia.,School of Life Sciences, La Trobe University, Bundoora, VIC 3086, Australia
| | - Nathan S Hart
- Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
| | - Kate L Sanders
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
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20
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Sherratt E, Sanders KL, Watson A, Hutchinson MN, Lee MSY, Palci A. Heterochronic Shifts Mediate Ecomorphological Convergence in Skull Shape of Microcephalic Sea Snakes. Integr Comp Biol 2019; 59:616-624. [DOI: 10.1093/icb/icz033] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Abstract
Morphological variation among the viviparous sea snakes (Hydrophiinae), a clade of fully aquatic elapid snakes, includes an extreme “microcephalic” ecomorph that has a very small head atop a narrow forebody, while the hind body is much thicker (up to three times the forebody girth). Previous research has demonstrated that this morphology has evolved at least nine times as a consequence of dietary specialization on burrowing eels, and has also examined morphological changes to the vertebral column underlying this body shape. The question addressed in this study is what happens to the skull during this extreme evolutionary change? Here we use X-ray micro-computed tomography and geometric morphometric methods to characterize cranial shape variation in 30 species of sea snakes. We investigate ontogenetic and evolutionary patterns of cranial shape diversity to understand whether cranial shape is predicted by dietary specialization, and examine whether cranial shape of microcephalic species may be a result of heterochronic processes. We show that the diminutive cranial size of microcephalic species has a convergent shape that is correlated with trophic specialization to burrowing prey. Furthermore, their cranial shape is predictable for their size and very similar to that of juvenile individuals of closely related but non-microcephalic sea snakes. Our findings suggest that heterochronic changes (resulting in pedomorphosis) have driven cranial shape convergence in response to dietary specializations in sea snakes.
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Affiliation(s)
- Emma Sherratt
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Kate L Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Amy Watson
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Mark N Hutchinson
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
- College of Science and Engineering, Flinders University, Adelaide, South Australia 5042, Australia
| | - Michael S Y Lee
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
- College of Science and Engineering, Flinders University, Adelaide, South Australia 5042, Australia
| | - Alessandro Palci
- South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
- College of Science and Engineering, Flinders University, Adelaide, South Australia 5042, Australia
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21
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Crowe-Riddell JM, Williams R, Chapuis L, Sanders KL. Ultrastructural evidence of a mechanosensory function of scale organs (sensilla) in sea snakes (Hydrophiinae). R Soc Open Sci 2019; 6:182022. [PMID: 31183131 PMCID: PMC6502359 DOI: 10.1098/rsos.182022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 03/15/2019] [Indexed: 05/19/2023]
Abstract
The evolution of epidermal scales was a major innovation in lepidosaurs, providing a barrier to dehydration and physical stress, while functioning as a sensitive interface for detecting mechanical stimuli in the environment. In snakes, mechanoreception involves tiny scale organs (sensilla) that are concentrated on the surface of the head. The fully marine sea snakes (Hydrophiinae) are closely related to terrestrial hydrophiine snakes but have substantially more protruding (dome-shaped) scale organs that often cover a larger portion of the scale surface. Various divergent selection pressures in the marine environment could account for this morphological variation relating to detection of mechanical stimuli from direct contact with stimuli and/or indirect contact via water motion (i.e. 'hydrodynamic reception'), or co-option for alternate sensory or non-sensory functions. We addressed these hypotheses using immunohistochemistry, and light and electron microscopy, to describe the cells and nerve connections underlying scale organs in two sea snakes, Aipysurus laevis and Hydrophis stokesii. Our results show ultrastructural features in the cephalic scale organs of both marine species that closely resemble the mechanosensitive Meissner-like corpuscles that underlie terrestrial snake scale organs. We conclude that the scale organs of marine hydrophiines have retained a mechanosensory function, but future studies are needed to examine whether they are sensitive to hydrodynamic stimuli.
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Affiliation(s)
- Jenna M. Crowe-Riddell
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Ruth Williams
- Adelaide Microscopy, the Centre for Advanced Microscopy and Microanalysis, Adelaide, South Australia 5005, Australia
| | - Lucille Chapuis
- College of Life and Environmental Science, University of Exeter, Exeter EX4 4QD, UK
| | - Kate L. Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
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Crowe-Riddell JM, D'Anastasi BR, Nankivell JH, Rasmussen AR, Sanders KL. First records of sea snakes (Elapidae: Hydrophiinae) diving to the mesopelagic zone (>200 m). AUSTRAL ECOL 2019. [DOI: 10.1111/aec.12717] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jenna M. Crowe-Riddell
- School of Biological Sciences; University of Adelaide; Darling Building Adelaide South Australia 5005 Australia
| | - Blanche R. D'Anastasi
- College of Science and Engineering; James Cook University; Townsville Queensland Australia
- AIMS@JCU; Australian Institute of Marine Science and James Cook University; Townsville Queensland Australia
| | - James H. Nankivell
- School of Biological Sciences; University of Adelaide; Darling Building Adelaide South Australia 5005 Australia
| | - Arne R. Rasmussen
- The Royal Danish Academy of Fine Arts, School of Architecture, Design and Conservation; Copenhagen K Denmark
| | - Kate L. Sanders
- School of Biological Sciences; University of Adelaide; Darling Building Adelaide South Australia 5005 Australia
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23
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Sherratt E, Coutts FJ, Rasmussen AR, Sanders KL. Vertebral evolution and ontogenetic allometry: The developmental basis of extreme body shape divergence in microcephalic sea snakes. Evol Dev 2019; 21:135-144. [DOI: 10.1111/ede.12284] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 02/04/2019] [Accepted: 02/05/2019] [Indexed: 12/25/2022]
Affiliation(s)
- Emma Sherratt
- Department of Ecology and Evolutionary Biology School of Biological Sciences, The University of Adelaide Adelaide South Australia Australia
| | - Felicity J. Coutts
- Department of Ecology and Evolutionary Biology School of Biological Sciences, The University of Adelaide Adelaide South Australia Australia
- Earth Sciences Section, South Australian Museum Adelaide South Australia Australia
| | - Arne R. Rasmussen
- The Royal Danish Academy of Fine Arts, Schools of Architecture, Design and Conservation Copenhagen Denmark
| | - Kate L. Sanders
- Department of Ecology and Evolutionary Biology School of Biological Sciences, The University of Adelaide Adelaide South Australia Australia
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24
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Crowe-Riddell JM, Simões BF, Partridge JC, Hunt DM, Delean S, Schwerdt JG, Breen J, Ludington A, Gower DJ, Sanders KL. Phototactic tails: Evolution and molecular basis of a novel sensory trait in sea snakes. Mol Ecol 2019; 28:2013-2028. [PMID: 30767303 DOI: 10.1111/mec.15022] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 12/20/2018] [Accepted: 12/27/2018] [Indexed: 12/11/2022]
Abstract
Dermal phototaxis has been reported in a few aquatic vertebrate lineages spanning fish, amphibians and reptiles. These taxa respond to light on the skin of their elongate hind-bodies and tails by withdrawing under cover to avoid detection by predators. Here, we investigated tail phototaxis in sea snakes (Hydrophiinae), the only reptiles reported to exhibit this sensory behaviour. We conducted behavioural tests in 17 wild-caught sea snakes of eight species by illuminating the dorsal surface of the tail and midbody skin using cold white, violet, blue, green and red light. Our results confirmed phototactic tail withdrawal in the previously studied Aipysurus laevis, revealed this trait for the first time in A. duboisii and A. tenuis, and suggested that tail photoreceptors have peak spectral sensitivities between blue and green light (457-514 nm). Based on these results, and an absence of photoresponses in five Aipysurus and Hydrophis species, we tentatively infer that tail phototaxis evolved in the ancestor of a clade of six Aipysurus species (comprising 10% of all sea snakes). Quantifying tail damage, we found that the probability of sustaining tail injuries was not influenced by tail phototactic ability in snakes. Gene profiling showed that transcriptomes of both tail skin and body skin lacked visual opsins but contained melanopsin (opn4x) in addition to key genes of the retinal regeneration and phototransduction cascades. This work suggests that a nonvisual photoreceptor (e.g., Gq rhabdomeric) signalling pathway underlies tail phototaxis, and provides candidate gene targets for future studies of this unusual sensory innovation in reptiles.
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Affiliation(s)
- Jenna M Crowe-Riddell
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia.,Department of Biology, University of Florida, Gainesville, Florida
| | - Bruno F Simões
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia.,School of Earth Sciences, University of Bristol, Bristol, UK
| | - Julian C Partridge
- School of Biological Sciences and Oceans Institute, University of Western Australia, Crawley, Western Australia, Australia
| | - David M Hunt
- School of Biological Sciences and Oceans Institute, University of Western Australia, Crawley, Western Australia, Australia.,Centre for Ophthalmology and Vision Science, Lions Eye Institute, University of Western Australia, Nedlands, Western Australia, Australia
| | - Steven Delean
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
| | - Julian G Schwerdt
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
| | - James Breen
- Robinson Research Institute, University of Adelaide, North Adelaide, South Australia, Australia.,Bioinformatics Hub, University of Adelaide, Adelaide, South Australia, Australia.,South Australian Health and Medical Research Institute (SAHMRI), Adelaide, South Australia, Australia
| | - Alastair Ludington
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia.,Bioinformatics Hub, University of Adelaide, Adelaide, South Australia, Australia
| | - David J Gower
- Department of Life Sciences, The Natural History Museum, London, UK
| | - Kate L Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
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Nitschke CR, Hourston M, Udyawer V, Sanders KL. Rates of population differentiation and speciation are decoupled in sea snakes. Biol Lett 2018; 14:rsbl.2018.0563. [PMID: 30333264 DOI: 10.1098/rsbl.2018.0563] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 09/14/2018] [Indexed: 11/12/2022] Open
Abstract
Comparative phylogeography can inform many macroevolutionary questions, such as whether species diversification is limited by rates of geographical population differentiation. We examined the link between population genetic structure and species diversification in the fully aquatic sea snakes (Hydrophiinae) by comparing mitochondrial phylogeography across northern Australia in 16 species from two closely related clades that show contrasting diversification dynamics. Contrary to expectations from theory and several empirical studies, our results show that, at the geographical scale studied here, rates of population differentiation and speciation are not positively linked in sea snakes. The eight species sampled from the rapidly speciating Hydrophis clade have weak population differentiation that lacks geographical structure. By contrast, all eight sampled Aipysurus-Emydocephalus species show clear geographical patterns and many deep intraspecific splits, but have threefold slower speciation rates. Alternative factors, such as ecological specialization, species duration and geographical range size, may underlie rapid speciation in sea snakes.
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Affiliation(s)
- Charlotte R Nitschke
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Mathew Hourston
- The Department of Primary Industries and Regional Development, Perth, Western Australia, Australia
| | - Vinay Udyawer
- Australian Institute of Marine Science, Darwin, Northern Territory 0810, Australia
| | - Kate L Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
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26
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Sherratt E, Rasmussen AR, Sanders KL. Trophic specialization drives morphological evolution in sea snakes. R Soc Open Sci 2018; 5:172141. [PMID: 29657807 PMCID: PMC5882731 DOI: 10.1098/rsos.172141] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 02/26/2018] [Indexed: 05/19/2023]
Abstract
Viviparous sea snakes are the most rapidly speciating reptiles known, yet the ecological factors underlying this radiation are poorly understood. Here, we reconstructed dated trees for 75% of sea snake species and quantified body shape (forebody relative to hindbody girth), maximum body length and trophic diversity to examine how dietary specialization has influenced morphological diversification in this rapid radiation. We show that sea snake body shape and size are strongly correlated with the proportion of burrowing prey in the diet. Specialist predators of burrowing eels have convergently evolved a 'microcephalic' morphotype with dramatically reduced forebody relative to hindbody girth and intermediate body length. By comparison, snakes that predominantly feed on burrowing gobies are generally short-bodied and small-headed, but there is no evidence of convergent evolution. The eel specialists also exhibit faster rates of size and shape evolution compared to all other sea snakes, including those that feed on gobies. Our results suggest that trophic specialization to particular burrowing prey (eels) has invoked strong selective pressures that manifest as predictable and rapid morphological changes. Further studies are needed to examine the genetic and developmental mechanisms underlying these dramatic morphological changes and assess their role in sea snake speciation.
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Affiliation(s)
- Emma Sherratt
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Arne R. Rasmussen
- The Royal Danish Academy of Fine Arts, Schools of Architecture, Design and Conservation, Copenhagen K, Denmark
| | - Kate L. Sanders
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
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27
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Crowe-Riddell JM, Snelling EP, Watson AP, Suh AK, Partridge JC, Sanders KL. The evolution of scale sensilla in the transition from land to sea in elapid snakes. Open Biol 2017; 6:rsob.160054. [PMID: 27278646 PMCID: PMC4929937 DOI: 10.1098/rsob.160054] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 05/13/2016] [Indexed: 11/12/2022] Open
Abstract
Scale sensilla are small tactile mechanosensory organs located on the head scales of many squamate reptiles (lizards and snakes). In sea snakes and sea kraits (Elapidae: Hydrophiinae), these scale organs are presumptive scale sensilla that purportedly function as both tactile mechanoreceptors and potentially as hydrodynamic receptors capable of sensing the displacement of water. We combined scanning electron microscopy, silicone casting of the skin and quadrate sampling with a phylogenetic analysis to assess morphological variation in sensilla on the postocular head scale(s) across four terrestrial, 13 fully aquatic and two semi-aquatic species of elapids. Substantial variation exists in the overall coverage of sensilla (0.8-6.5%) among the species sampled and is broadly overlapping in aquatic and terrestrial lineages. However, two observations suggest a divergent, possibly hydrodynamic sensory role of sensilla in sea snake and sea krait species. First, scale sensilla are more protruding (dome-shaped) in aquatic species than in their terrestrial counterparts. Second, exceptionally high overall coverage of sensilla is found only in the fully aquatic sea snakes, and this attribute appears to have evolved multiple times within this group. Our quantification of coverage as a proxy for relative 'sensitivity' represents the first analysis of the evolution of sensilla in the transition from terrestrial to marine habitats. However, evidence from physiological and behavioural studies is needed to confirm the functional role of scale sensilla in sea snakes and sea kraits.
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Affiliation(s)
- Jenna M Crowe-Riddell
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Edward P Snelling
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng 2193, South Africa
| | - Amy P Watson
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Anton Kyuseop Suh
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Julian C Partridge
- School of Animal Biology and Oceans Institute, University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Kate L Sanders
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
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28
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Simões BF, Sampaio FL, Loew ER, Sanders KL, Fisher RN, Hart NS, Hunt DM, Partridge JC, Gower DJ. Multiple rod-cone and cone-rod photoreceptor transmutations in snakes: evidence from visual opsin gene expression. Proc Biol Sci 2016; 283:rspb.2015.2624. [PMID: 26817768 DOI: 10.1098/rspb.2015.2624] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 01/05/2016] [Indexed: 11/12/2022] Open
Abstract
In 1934, Gordon Walls forwarded his radical theory of retinal photoreceptor 'transmutation'. This proposed that rods and cones used for scotopic and photopic vision, respectively, were not fixed but could evolve into each other via a series of morphologically distinguishable intermediates. Walls' prime evidence came from series of diurnal and nocturnal geckos and snakes that appeared to have pure-cone or pure-rod retinas (in forms that Walls believed evolved from ancestors with the reverse complement) or which possessed intermediate photoreceptor cells. Walls was limited in testing his theory because the precise identity of visual pigments present in photoreceptors was then unknown. Subsequent molecular research has hitherto neglected this topic but presents new opportunities. We identify three visual opsin genes, rh1, sws1 and lws, in retinal mRNA of an ecologically and taxonomically diverse sample of snakes central to Walls' theory. We conclude that photoreceptors with superficially rod- or cone-like morphology are not limited to containing scotopic or photopic opsins, respectively. Walls' theory is essentially correct, and more research is needed to identify the patterns, processes and functional implications of transmutation. Future research will help to clarify the fundamental properties and physiology of photoreceptors adapted to function in different light levels.
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Affiliation(s)
- Bruno F Simões
- Department of Life Sciences, The Natural History Museum, London SW7 5BD, UK
| | - Filipa L Sampaio
- Department of Life Sciences, The Natural History Museum, London SW7 5BD, UK
| | - Ellis R Loew
- Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Kate L Sanders
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5000, Australia
| | - Robert N Fisher
- US Geological Survey, Western Ecological Research Center, San Diego, CA 92101, USA
| | - Nathan S Hart
- Department of Biological Science, Macquarie University, New South Wales 2109, Australia
| | - David M Hunt
- School of Animal Biology, The University of Western Australia, Perth, Western Australia 6009, Australia Lions Eye Institute, University of Western Australia, Perth 6009, Australia
| | - Julian C Partridge
- School of Animal Biology, The University of Western Australia, Perth, Western Australia 6009, Australia School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK
| | - David J Gower
- Department of Life Sciences, The Natural History Museum, London SW7 5BD, UK
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Lee MSY, Sanders KL, King B, Palci A. Diversification rates and phenotypic evolution in venomous snakes (Elapidae). R Soc Open Sci 2016; 3:150277. [PMID: 26909162 PMCID: PMC4736917 DOI: 10.1098/rsos.150277] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 12/08/2015] [Indexed: 05/19/2023]
Abstract
The relationship between rates of diversification and of body size change (a common proxy for phenotypic evolution) was investigated across Elapidae, the largest radiation of highly venomous snakes. Time-calibrated phylogenetic trees for 175 species of elapids (more than 50% of known taxa) were constructed using seven mitochondrial and nuclear genes. Analyses using these trees revealed no evidence for a link between speciation rates and changes in body size. Two clades (Hydrophis, Micrurus) show anomalously high rates of diversification within Elapidae, yet exhibit rates of body size evolution almost identical to the general elapid 'background' rate. Although correlations between speciation rates and rates of body size change exist in certain groups (e.g. ray-finned fishes, passerine birds), the two processes appear to be uncoupled in elapid snakes. There is also no detectable shift in diversification dynamics associated with the colonization of Australasia, which is surprising given that elapids appear to be the first clade of venomous snakes to reach the continent.
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Affiliation(s)
- Michael S. Y. Lee
- Earth Sciences Section, South Australian Museum, North Terrace, Adelaide, SA 5000, Australia
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
- School of Biological Sciences, Flinders University, PO Box 2100, Adelaide, SA 5001, Australia
- Author for correspondence: Michael S. Y. Lee e-mail:
| | - Kate L. Sanders
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Benedict King
- School of Biological Sciences, Flinders University, PO Box 2100, Adelaide, SA 5001, Australia
| | - Alessandro Palci
- Earth Sciences Section, South Australian Museum, North Terrace, Adelaide, SA 5000, Australia
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
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30
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Laustsen AH, Gutiérrez JM, Rasmussen AR, Engmark M, Gravlund P, Sanders KL, Lohse B, Lomonte B. Danger in the reef: Proteome, toxicity, and neutralization of the venom of the olive sea snake, Aipysurus laevis. Toxicon 2015; 107:187-96. [PMID: 26169672 DOI: 10.1016/j.toxicon.2015.07.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 07/03/2015] [Accepted: 07/08/2015] [Indexed: 10/23/2022]
Abstract
Four specimens of the olive sea snake, Aipysurus laevis, were collected off the coast of Western Australia, and the venom proteome was characterized and quantitatively estimated by RP-HPLC, SDS-PAGE, and MALDI-TOF-TOF analyses. A. laevis venom is remarkably simple and consists of phospholipases A2 (71.2%), three-finger toxins (3FTx; 25.3%), cysteine-rich secretory proteins (CRISP; 2.5%), and traces of a complement control module protein (CCM; 0.2%). Using a Toxicity Score, the most lethal components were determined to be short neurotoxins. Whole venom had an intravenous LD50 of 0.07 mg/kg in mice and showed a high phospholipase A2 activity, but no proteinase activity in vitro. Preclinical assessment of neutralization and ELISA immunoprofiling showed that BioCSL Sea Snake Antivenom was effective in cross-neutralizing A. laevis venom with an ED50 of 821 μg venom per mL antivenom, with a binding preference towards short neurotoxins, due to the high degree of conservation between short neurotoxins from A. laevis and Enhydrina schistosa venom. Our results point towards the possibility of developing recombinant antibodies or synthetic inhibitors against A. laevis venom due to its simplicity.
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Affiliation(s)
- Andreas H Laustsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - José María Gutiérrez
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Arne R Rasmussen
- Royal Danish Academy of Fine Arts, Schools of Architecture, Design and Conservation, Denmark
| | - Mikael Engmark
- Department of Systems Biology, Technical University of Denmark, Denmark
| | | | - Kate L Sanders
- School of Earth & Environmental Sciences, University of Adelaide, Australia
| | - Brian Lohse
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Bruno Lomonte
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica.
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Sanders KL, Schroeder T, Guinea ML, Rasmussen AR. Molecules and morphology reveal overlooked populations of two presumed extinct Australian sea snakes (Aipysurus: Hydrophiinae). PLoS One 2015; 10:e0115679. [PMID: 25671608 PMCID: PMC4324969 DOI: 10.1371/journal.pone.0115679] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 11/14/2014] [Indexed: 11/30/2022] Open
Abstract
The critically endangered leaf-scaled (Aipysurus foliosquamaI) and short-nosed (A. apraefrontalis) sea snakes are currently recognised only from Ashmore and Hibernia reefs ~600km off the northwest Australian coast. Steep population declines in both species were documented over 15 years and neither has been sighted on dedicated surveys of Ashmore and Hibernia since 2001. We examine specimens of these species that were collected from coastal northwest Australian habitats up until 2010 (A.foliosquama) and 2012 (A. apraefrontalis) and were either overlooked or treated as vagrants in conservation assessments. Morphological variation and mitochondrial sequence data confirm the assignment of these coastal specimens to A. foliosquama (Barrow Island, and offshore from Port Hedland) and A.apraefrontalis (Exmouth Gulf, and offshore from Roebourne and Broome). Collection dates, and molecular and morphological variation between coastal and offshore specimens, suggest that the coastal specimens are not vagrants as previously suspected, but instead represent separate breeding populations. The newly recognised populations present another chance for leaf-scaled and short-nosed sea snakes, but coastal habitats in northwest Australia are widely threatened by infrastructure developments and sea snakes are presently omitted from environmental impact assessments for industry. Further studies are urgently needed to assess these species’ remaining distributions, population structure, and extent of occurrence in protected areas.
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Affiliation(s)
- Kate L. Sanders
- School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia 5000, Australia
- * E-mail:
| | - Tina Schroeder
- School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia 5000, Australia
| | - Michael L. Guinea
- Research Institute of the Environment and Livelihoods, Charles Darwin University, Darwin, Northern Territories 0909, Australia
| | - Arne R. Rasmussen
- The Royal Danish Academy of Fine Arts, School of Architecture, Design and Conservation, Esplanaden 34, DK-1263, Copenhagen, Denmark
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Ukuwela KDB, de Silva A, Mumpuni, Fry BG, Sanders KL. Multilocus phylogeography of the sea snakeHydrophis curtusreveals historical vicariance and cryptic lineage diversity. ZOOL SCR 2014. [DOI: 10.1111/zsc.12070] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kanishka D. B. Ukuwela
- School of Earth and Environmental Sciences; University of Adelaide; Darling Building Adelaide SA 5005 Australia
| | - Anslem de Silva
- Amphibia and Reptile research Organization of Sri Lanka; 15/1, Dolosbage Rd. Gampola Sri Lanka
| | - Mumpuni
- Museum of Zoology Bogor; Puslit Biology-LIPI; Cibinong Indonesia
| | - Bryan G. Fry
- Venom Evolution Laboratory; School of Biological Sciences; University of Queensland; Brisbane QLD 4072 Australia
| | - Kate L. Sanders
- School of Earth and Environmental Sciences; University of Adelaide; Darling Building Adelaide SA 5005 Australia
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Sanders KL, Rasmussen AR, Mumpuni, Elmberg J, de Silva A, Guinea ML, Lee MSY. Recent rapid speciation and ecomorph divergence in Indo-Australian sea snakes. Mol Ecol 2013; 22:2742-59. [PMID: 23506038 DOI: 10.1111/mec.12291] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 01/09/2013] [Accepted: 01/22/2013] [Indexed: 11/30/2022]
Abstract
The viviparous sea snakes (Hydrophiinae) are a young radiation of at least 62 species that display spectacular morphological diversity and high levels of local sympatry. To shed light on the mechanisms underlying sea snake diversification, we investigated recent speciation and eco-morphological differentiation in a clade of four nominal species with overlapping ranges in Southeast Asia and Australia. Analyses of morphology and stomach contents identified the presence of two distinct ecomorphs: a 'macrocephalic' ecomorph that reaches >2 m in length, has a large head and feeds on crevice-dwelling eels and gobies; and a 'microcephalic' ecomorph that rarely exceeds 1 m in length, has a small head and narrow fore-body and hunts snake eels in burrows. Mitochondrial sequences show a lack of reciprocal monophyly between ecomorphs and among putative species. However, individual assignment based on newly developed microsatellites separated co-distributed specimens into four significantly differentiated clusters corresponding to morphological species designations, indicating limited recent gene flow and progress towards speciation. A coalescent species tree (based on mitochondrial and nuclear sequences) and isolation-migration model (mitochondrial and microsatellite markers) suggest between one and three transitions between ecomorphs within the last approximately 1.2 million to approximately 840,000 years. In particular, the macrocephalic 'eastern' population of Hydrophis cyanocinctus and microcephalic H. melanocephalus appear to have diverged very recently and rapidly, resulting in major phenotypic differences and restriction of gene flow in sympatry. These results highlight the viviparous sea snakes as a promising system for speciation studies in the marine environment.
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Affiliation(s)
- Kate L Sanders
- School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA, Australia.
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Kumar AB, Sanders KL, George S, Murphy JC. The status of Eurostus dussumierii and Hypsirhina chinensis (Reptilia, Squamata, Serpentes): with comments on the origin of salt tolerance in homalopsid snakes. SYST BIODIVERS 2012. [DOI: 10.1080/14772000.2012.751940] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- A. Biju Kumar
- a Department of Aquatic Biology & Fisheries , University of Kerala , Thiruvananthapuram , 695 581 , Kerala , India
| | - Kate L. Sanders
- b School of Earth and Environmental Sciences , University of Adelaide , Adelaide , Australia
| | - Sanil George
- c Chemical Biology Group , Rajiv Gandhi Centre for Biotechnology , Thiruvananthapuram , 695 014 , Kerala , India
| | - John C. Murphy
- d Division of Amphibians and Reptiles , Field Museum of Natural History , 1400 S, Lake Shore Drive, Chicago , IL , 60605–2496 , USA
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Ukuwela KDB, de Silva A, Mumpuni, Fry BG, Lee MSY, Sanders KL. Molecular evidence that the deadliest sea snake Enhydrina schistosa (Elapidae: Hydrophiinae) consists of two convergent species. Mol Phylogenet Evol 2012; 66:262-9. [PMID: 23044399 DOI: 10.1016/j.ympev.2012.09.031] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 09/07/2012] [Accepted: 09/26/2012] [Indexed: 11/26/2022]
Abstract
We present a striking case of phenotypic convergence within the speciose and taxonomically unstable Hydrophis group of viviparous sea snakes. Enhydrina schistosa, the 'beaked sea snake', is abundant in coastal and inshore habitats throughout the Asian and Australian regions, where it is responsible for the large majority of recorded deaths and injuries from sea snake bites. Analyses of five independent mitochondrial and nuclear loci for populations spanning Australia, Indonesia and Sri Lanka indicate that this 'species' actually consists of two distinct lineages in Asia and Australia that are not closest relatives. As a result, Australian "E. schistosa" are elevated to species status and provisionally referred to Enhydrinazweifeli. Convergence in the characteristic 'beaked' morphology of these species is probably associated with the wide gape required to accommodate their spiny prey. Our findings have important implications for snake bite management in light of the medical importance of beaked sea snakes and the fact that the only sea snake anti-venom available is raised against Malaysian E. schistosa.
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Affiliation(s)
- Kanishka D B Ukuwela
- Darling Building, School of Earth and Environmental Sciences, University of Adelaide, North Terrace, SA 5005, Australia
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Sanders KL, Lee MSY, Mumpuni, Bertozzi T, Rasmussen AR. Multilocus phylogeny and recent rapid radiation of the viviparous sea snakes (Elapidae: Hydrophiinae). Mol Phylogenet Evol 2012; 66:575-91. [PMID: 23026811 DOI: 10.1016/j.ympev.2012.09.021] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 09/10/2012] [Accepted: 09/17/2012] [Indexed: 10/27/2022]
Abstract
The viviparous sea snakes (Hydrophiinae: Hydrophiini) comprise a young but morphologically and ecologically diverse clade distributed throughout the Indo-Pacific. Despite presenting a very promising model for marine diversification studies, many relationships among the 62 species and 16 genera in Hydrophiini remain unresolved. Here, we extend previous taxonomic and genomic sampling for Hydrophiini using three mitochondrial fragments and five nuclear loci for multiple individuals of 39 species in 15 genera. Our results highlight many of the impediments to inferring phylogenies in recent rapid radiations, including low variation at all five nuclear markers, and conflicting relationships supported by mitochondrial and nuclear trees. However, concatenated Bayesian and likelihood analyses, and a multilocus coalescent tree, recovered concordant support for primary clades and several previously unresolved inter-specific groupings. The Aipysurus group is monophyletic, with egg-eating specialists forming separate, early-diverging lineages. All three monotypic semi-aquatic genera (Ephalophis, Parahydrophis and Hydrelaps) are robustly placed as early diverging lineages along the branch leading to the Hydrophis group, with Ephalophis recovered as sister to Parahydrophis. The molecular phylogeny implies extensive evolutionary convergence in feeding adaptations within the Hydrophis group, especially the repeated evolution of small-headed (microcephalic) forms. Microcephalophis (Hydrophis) gracilis is robustly recovered as a relatively distant sister lineage to all other sampled Hydrophis group species, here termed the 'core Hydrophis group'. Within the 'core Hydrophis group', Hydrophis is recovered as broadly paraphyletic, with several other genera nested within it (Pelamis, Enhydrina, Astrotia, Thalassophina, Acalyptophis, Kerilia, Lapemis, Disteira). Instead of erecting multiple new genera, we recommend dismantling the latter (mostly monotypic) genera and recognising a single genus, Hydrophis Latreille 1802, for the core Hydrophis group. Estimated divergence times suggest that all Hydrophiini last shared a common ancestor ∼6million years ago, but that the majority of extant lineages diversified over the last ∼3.5million years. The core Hydrophis group is a young and rapidly speciating clade, with 26 sampled species and 9 genera and dated at only ∼1.5-3million years old.
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Affiliation(s)
- Kate L Sanders
- School of Earth and Environmental Sciences, University of Adelaide, South Australia 5000, Australia.
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Sanders KL, Gardner MG. Isolation, via 454 sequencing, characterisation and transferability of twelve microsatellite loci for Hydrophis spiralis, the yellow sea snake (Serpentes: Elapidae). CONSERV GENET RESOUR 2012. [DOI: 10.1007/s12686-012-9715-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Rasmussen AR, Elmberg J, Sanders KL, Gravlund P. Rediscovery of the Rare Sea Snake Hydrophis parviceps Smith 1935: Identification and Conservation Status. COPEIA 2012. [DOI: 10.1643/ch-11-116] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Sanders KL, Rasmussen AR, Elmberg J. Independent innovation in the evolution of paddle-shaped tails in viviparous sea snakes (Elapidae: Hydrophiinae). Integr Comp Biol 2012; 52:311-20. [PMID: 22634358 DOI: 10.1093/icb/ics066] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The viviparous sea snakes (Hydrophiinae) comprise ~90% of living marine reptiles and display many physical and behavioral adaptations for breathing, diving, and achieving osmotic balance in marine habitats. Among the most important innovations found in marine snakes are their paddle-shaped (dorsoventrally expanded) tails, which provide propulsive thrust in the dense aquatic medium. Here, we reconstruct the evolution of caudal paddles in viviparous sea snakes using a dated molecular phylogeny for all major lineages and computed tomography of internal osteological structures. Bayesian ancestral state reconstructions show that extremely large caudal paddles supported by elongated vertebral processes are unlikely to have been present in the most recent common ancestor of extant sea snakes. Instead, these characters appear to have been acquired independently in two highly marine lineages of relatively recent origin. Both the Aipysurus and Hydrophis lineages have elongated neural spines that support the dorsal edge of their large paddles. However, whereas in the Aipysurus lineage the ventral edge of the paddle is supported by elongated haemapophyses, this support is provided by elongated and ventrally directed pleurapophyses in the Hydrophis lineage. Three semi-marine lineages (Hydrelaps, Ephalophis, and Parahydrophis) form the sister group to the Hydrophis clade and have small paddles with poorly developed dorsal and ventral supports, consistent with their amphibious lifestyle. Overall, our results suggest that not only are the viviparous hydrophiines the only lineage of marine snakes to have acquired extremely large, skeletally supported caudal paddles but also that this innovation has occurred twice in the group in the past ~2-6 million years.
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Affiliation(s)
- Kate L Sanders
- School of Earth and Environmental Sciences, University of Adelaide, South Australia 5000, Australia.
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Gökmen-Polar Y, Toroni RA, Goswami C, Sanders KL, Mehta R, Sirimalle U, Tanasa B, Shen C, Li L, Ivan M, Badve S, Sledge GW. P5-06-01: Gene Expression Analysis of Resistance to Bevacizumab in a VEGF-Reinforced Xenograft Model of ER-Positive Breast Cancer. Cancer Res 2011. [DOI: 10.1158/0008-5472.sabcs11-p5-06-01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Background: Bevacizumab, a monoclonal antibody targeting vascular endothelial growth factor (VEGF), had promising therapeutic efficacy in breast cancer. However, intrinsic or acquired resistance is common in the clinic. To improve our understanding of the underlying mechanisms of resistance to bevacizumab (BEV), we report the gene expression analysis of resistance to bevacizumab in a VEGF-overexpressing xenograft model of ER-positive breast cancer.
Methods: We developed a nude mouse xenograft model of resistance to anti-VEGF therapy with BEV in which MCF-7 control (ML20) or MCF-7 VEGF (MV165) transfectants were implanted in mammary fat pads, allowed to grow, then treated with BEV, with collection of tumor at early or late time points (while responding (R) to or progressing (NR) on anti-VEGF therapy). To elucidate differentially expressed gene profiling associated with tumor resistance to BEV, we performed whole-genome gene expression analysis (Human WG-6v2 Expression Beadchips, Illumina) and miRNA profiling (TaqMan ***ArrayHuman MicroRNAA+B Cards Set v3.0, Applied Biosystems). Validation of the chosen genes was performed using quantitative real-time RT-PCR (qRT-PCR).
Results: Gene expression analysis revealed differentially regulated genes in the MV165-NR group compared with the MV165-R group. Among the significant genes, Follistatin (FST) and HEY2 were the top genes upregulated in NR compared to R by ANOVA. Expression of HEY2 is induced by the Notch signaling pathway. Using qRT-PCR, we validated the expression of FST and Notch in our system. FST was significantly decreased (Fold change= −3.2; P=0.03) in the R group compared with vehicle in MV165 xenografts. In contrast to R group, FST was upregulated significantly (Fold change= 9.3; P=0.05) in the NR group. Notch4 displayed increased levels of expression in NR group, but it did not reach significance (P=0.23). In addition, correlation of mRNA and miRNA profiles showed that miRNAs targeting FST and Notch4 were differentially regulated in NR group compared to R group in MV165 xenograft tumors. Among the miRNAs, TGF-β-induced oncomiR miR-181a is up-regulated in NR and targets both FST and Notch4. Other miRNAs that target both Notch4 and FST include miR-1, miR-133a, miR-133b, and mir-449b. Conclusion: Our data serve as a potential mechanistic explanation for acquired resistance to bevacizumab. These data may shed light on the transitory effect of BEV observed in the E2100 firstline metastatic breast cancer trial, where VEGF-targeted therapy prolongs progression-free survival in metastatic breast cancer without improving overall survival.
Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-06-01.
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Affiliation(s)
- Y Gökmen-Polar
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - RA Toroni
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - C Goswami
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - KL Sanders
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - R Mehta
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - U Sirimalle
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - B Tanasa
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - C Shen
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - L Li
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - M Ivan
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - S Badve
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
| | - GW Sledge
- 1Indiana University School of Medicine, Indianapolis, IN; University of Medicine and Pharmac, La Jolla, CA
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Gökmen-Polar Y, Toroni RA, Goswami C, Sanders KL, Sirimalle U, Mehta R, Li L, Ivan M, Badve S, Sledge GW. P3-04-02: Bevacizumab Treatment Alters Intrinsic Subtypes in a VEGF-Reinforced Xenograft Model of ER-Positive Breast Cancer. Cancer Res 2011. [DOI: 10.1158/0008-5472.sabcs11-p3-04-02] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Background: Anti-vascular endothelial growth factor (anti-VEGF) therapy improves disease-free but not overall survival in metastatic breast cancer. To seek further insight on resistance to anti-VEGF antibody bevacizumab (BEV) at the molecular level, we developed breast cancer xenograft models allowing comparison of tumor response at different time-points. Here we report the gene expression and miRNA analyses of response and non-response to BEV in these models.
Methods: MCF-7 cells transfected with control vector (ML20) or VEGF (MV165) were implanted into the mammary fat pads of athymic mice. Tumors from short-term treatment with BEV (3 weeks; Responders to BEV, R) or long-term treatment (8 weeks; Non-Responders, NR) or with vehicle control group (V) were subjected to whole-genome gene expression analysis (Human WG-6v2 Expression Beadchips, Illumina) and miRNA profiling (TaqMan ArrayHuman MicroRNA A+B Cards Set v3.0, Applied Biosystems).Validation of the chosen genes was performed using quantitative real-time RT-PCR (qRT-PCR) and Immunohistochemistry (IHC). Results: Short-term treatment to BEV (3 weeks; 5 mg/kg, i.p./twice weekly) inhibited primary tumor growth significantly in MV165 xenografts compared with vehicle control, whereas BEV treatment did not affect the tumor growth in the ML20 model. MV165 xenografts progressed after 8 weeks of BEV treatment. Gene set enrichment analysis (GSEA) revealed that luminal A-related gene sets were enriched in MV165-R compared to MV165-NR group including DESMEDT (ESR1), SMID_Breast_Cancer_Luminal_A_up, and MASSARWEH_ Tamoxifen_Resistance_ Down. Myoepithelial-specific gene sets were upregulated in both the R and NR groups compared with the vehicle group. qRT-PCR analysis showed that estrogen receptor alpha (ESR1) representative for luminal A decreased significantly in the MV-165-NR group (P=0.001) compared to vehicle. In contrast, Cytokeratin 5 (KRT5) levels increased significantly in both R (P=0.02) and NR (P=0.03) groups. In addition, KRT14 was upregulated in R (P= 0.04) and in NR (P=0.14) group in comparison with the vehicle group, suggesting the upregulation of myoepithelial phenotype specific to BEV treated MV165 model, but not ML20 model. Similar results were obtained by IHC. Consistent with mRNA changes, ESR1 regulated miRNA such as miR-107 (P=0.007) and miRNA important in tamoxifen resistance such as mir-451 (P= 0.0003) were also altered in MV165-NR group compared to vehicle. Conclusion: These results suggest that treatment with BEV may alter the intrinsic subtypes in the presence of VEGF expression. These data may help to explain the variable results to anti-VEGF therapy based on the duration of BEV treatment.
Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-04-02.
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Affiliation(s)
| | - RA Toroni
- 1Indiana University School of Medicine, Indianapolis, IN
| | - C Goswami
- 1Indiana University School of Medicine, Indianapolis, IN
| | - KL Sanders
- 1Indiana University School of Medicine, Indianapolis, IN
| | - U Sirimalle
- 1Indiana University School of Medicine, Indianapolis, IN
| | - R Mehta
- 1Indiana University School of Medicine, Indianapolis, IN
| | - L Li
- 1Indiana University School of Medicine, Indianapolis, IN
| | - M Ivan
- 1Indiana University School of Medicine, Indianapolis, IN
| | - S Badve
- 1Indiana University School of Medicine, Indianapolis, IN
| | - GW Sledge
- 1Indiana University School of Medicine, Indianapolis, IN
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Murphy JC, Mumpuni, Sanders KL. First molecular evidence for the phylogenetic placement of the enigmatic snake genus Brachyorrhos (Serpentes: Caenophidia). Mol Phylogenet Evol 2011; 61:953-7. [DOI: 10.1016/j.ympev.2011.08.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 07/20/2011] [Accepted: 08/09/2011] [Indexed: 11/16/2022]
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Diraison F, Hayward K, Sanders KL, Brozzi F, Lajus S, Hancock J, Francis JE, Ainscow E, Bommer UA, Molnar E, Avent ND, Varadi A. Translationally controlled tumour protein (TCTP) is a novel glucose-regulated protein that is important for survival of pancreatic beta cells. Diabetologia 2011; 54:368-79. [PMID: 21063673 DOI: 10.1007/s00125-010-1958-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 09/27/2010] [Indexed: 12/25/2022]
Abstract
AIMS/HYPOTHESIS This study used proteomics and biochemical approaches to identify novel glucose-regulated proteins and to unveil their role in pancreatic beta cell function. Translationally controlled tumour protein (TCTP) was identified to be one such protein, and further investigations into its function and regulation were carried out. METHODS Global protein profiling of beta cell homogenates following glucose stimulation was performed using two-dimensional gel electrophoresis. Proteins were identified by mass spectroscopy analysis. Immunoblotting was used to investigate alterations in TCTP protein levels in response to glucose stimulation or cell stress induced by palmitate. To investigate the biological function of TCTP, immunolocalisation, gene knockdown and overexpression of Tctp (also known as Tpt1) were performed. Apoptosis was measured in Tctp knockdown or Tctp-overexpressing cells. Glucose-stimulated insulin secretion was carried out in Tctp knockdown cells. RESULTS TCTP was identified as a novel glucose-regulated protein, the level of which is increased at stimulatory glucose concentration. Glucose also induced TCTP dephosphorylation and its partial translocation to the mitochondria and the nucleus. TCTP protein levels were downregulated in response to cell stress induced by palmitate or thapsigargin treatments. Gene knockdown by small interfering RNA led to increased apoptosis, whereas overproduction of TCTP prevented palmitate-induced cell death. CONCLUSIONS/INTERPRETATION Regulation of TCTP protein levels by glucose is likely to be an important cyto-protective mechanism for pancreatic beta cells against damage caused by hyperglycaemia. In contrast, high concentration of palmitate causes cell stress, reduction in TCTP levels and consequently reduced cell viability. Our results imply that TCTP levels influence the sensitivity of beta cells to apoptosis.
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Affiliation(s)
- F Diraison
- Centre for Research in Biomedicine, Faculty of Health and Life Sciences, University of the West of England, Bristol BS16 1QY, UK
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Hoffmann M, Hilton-Taylor C, Angulo A, Böhm M, Brooks TM, Butchart SHM, Carpenter KE, Chanson J, Collen B, Cox NA, Darwall WRT, Dulvy NK, Harrison LR, Katariya V, Pollock CM, Quader S, Richman NI, Rodrigues ASL, Tognelli MF, Vié JC, Aguiar JM, Allen DJ, Allen GR, Amori G, Ananjeva NB, Andreone F, Andrew P, Aquino Ortiz AL, Baillie JEM, Baldi R, Bell BD, Biju SD, Bird JP, Black-Decima P, Blanc JJ, Bolaños F, Bolivar-G W, Burfield IJ, Burton JA, Capper DR, Castro F, Catullo G, Cavanagh RD, Channing A, Chao NL, Chenery AM, Chiozza F, Clausnitzer V, Collar NJ, Collett LC, Collette BB, Cortez Fernandez CF, Craig MT, Crosby MJ, Cumberlidge N, Cuttelod A, Derocher AE, Diesmos AC, Donaldson JS, Duckworth JW, Dutson G, Dutta SK, Emslie RH, Farjon A, Fowler S, Freyhof J, Garshelis DL, Gerlach J, Gower DJ, Grant TD, Hammerson GA, Harris RB, Heaney LR, Hedges SB, Hero JM, Hughes B, Hussain SA, Icochea M J, Inger RF, Ishii N, Iskandar DT, Jenkins RKB, Kaneko Y, Kottelat M, Kovacs KM, Kuzmin SL, La Marca E, Lamoreux JF, Lau MWN, Lavilla EO, Leus K, Lewison RL, Lichtenstein G, Livingstone SR, Lukoschek V, Mallon DP, McGowan PJK, McIvor A, Moehlman PD, Molur S, Muñoz Alonso A, Musick JA, Nowell K, Nussbaum RA, Olech W, Orlov NL, Papenfuss TJ, Parra-Olea G, Perrin WF, Polidoro BA, Pourkazemi M, Racey PA, Ragle JS, Ram M, Rathbun G, Reynolds RP, Rhodin AGJ, Richards SJ, Rodríguez LO, Ron SR, Rondinini C, Rylands AB, Sadovy de Mitcheson Y, Sanciangco JC, Sanders KL, Santos-Barrera G, Schipper J, Self-Sullivan C, Shi Y, Shoemaker A, Short FT, Sillero-Zubiri C, Silvano DL, Smith KG, Smith AT, Snoeks J, Stattersfield AJ, Symes AJ, Taber AB, Talukdar BK, Temple HJ, Timmins R, Tobias JA, Tsytsulina K, Tweddle D, Ubeda C, Valenti SV, van Dijk PP, Veiga LM, Veloso A, Wege DC, Wilkinson M, Williamson EA, Xie F, Young BE, Akçakaya HR, Bennun L, Blackburn TM, Boitani L, Dublin HT, da Fonseca GAB, Gascon C, Lacher TE, Mace GM, Mainka SA, McNeely JA, Mittermeier RA, Reid GM, Rodriguez JP, Rosenberg AA, Samways MJ, Smart J, Stein BA, Stuart SN. The impact of conservation on the status of the world's vertebrates. Science 2010; 330:1503-9. [PMID: 20978281 DOI: 10.1126/science.1194442] [Citation(s) in RCA: 662] [Impact Index Per Article: 47.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Using data for 25,780 species categorized on the International Union for Conservation of Nature Red List, we present an assessment of the status of the world's vertebrates. One-fifth of species are classified as Threatened, and we show that this figure is increasing: On average, 52 species of mammals, birds, and amphibians move one category closer to extinction each year. However, this overall pattern conceals the impact of conservation successes, and we show that the rate of deterioration would have been at least one-fifth again as much in the absence of these. Nonetheless, current conservation efforts remain insufficient to offset the main drivers of biodiversity loss in these groups: agricultural expansion, logging, overexploitation, and invasive alien species.
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Affiliation(s)
- Michael Hoffmann
- IUCN SSC Species Survival Commission, c/o United Nations Environment Programme World Conservation Monitoring Centre, 219 Huntingdon Road, Cambridge CB3 0DL, UK.
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Sanders KL, Hamidy A, Head JJ, Gower DJ. Phylogeny and divergence times of filesnakes (Acrochordus): inferences from morphology, fossils and three molecular loci. Mol Phylogenet Evol 2010; 56:857-67. [PMID: 20434568 DOI: 10.1016/j.ympev.2010.04.031] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 04/16/2010] [Accepted: 04/22/2010] [Indexed: 11/15/2022]
Abstract
Acrochordus is a species-poor but highly distinctive aquatic snake genus currently distributed from India to the western edge of the Pacific. We provide the first phylogeny for the three extant species using Bayesian and parsimony analyses of one mitochondrial and two nuclear gene sequences. Acrochordus javanicus is strongly recovered as sister to A. arafurae+A. granulatus, counter to expectations from superficial ecology, external phenotype and former taxonomy. We review and revise key fossil calibrations for dating snake divergences. Bayesian relaxed-clock analysis of the two nuclear loci yields deep interspecific divergences among extant species that occurred during the Miocene approximately 16 and approximately 20Mya (million years ago), pre-dating at least two of the three other living marine snake lineages. New morphological data for A. arafurae, and our molecular timescale, provide support for the placement of fossil taxon A. dehmi within the Acrochordus crown group, as sister to A. javanicus among nominate species. Finally, Acrochordus phylogeny provides an improved basis for taxon selection and character polarization in higher snake phylogenetics. Our study highlights the three Acrochordus species as old and highly distinct lineages that comprise an important component of the threatened Indo-Australian biodiversity.
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Affiliation(s)
- Kate L Sanders
- Darling Building School of Earth and Environmental Sciences, University of Adelaide, Adelaide 5005, Australia.
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Sanders KL, Lee MSY, Leys R, Foster R, Keogh JS. Molecular phylogeny and divergence dates for Australasian elapids and sea snakes (hydrophiinae): evidence from seven genes for rapid evolutionary radiations. J Evol Biol 2008; 21:682-95. [PMID: 18384538 DOI: 10.1111/j.1420-9101.2008.01525.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
One of the most prolific radiations of venomous snakes, the Australo-Melanesian Hydrophiinae includes approximately 100 species of Australasian terrestrial elapids plus all approximately 60 species of viviparous sea snakes. Here, we estimate hydrophiine relationships based on a large data set comprising 5800 bp drawn from seven genes (mitochondrial: ND4, cytb, 12S, 16S; nuclear: rag1, cmos, myh). These data were analysed using parsimony, likelihood and Bayesian methods to better resolve hydrophiine phylogeny and provide a timescale for the terrestrial and marine radiations. Among oviparous forms, Cacophis, Furina and Demansia are basal to other Australian elapids (core oxyuranines). The Melanesian Toxicocalamus and Aspidomorphus group with Demansia, indicating multiple dispersal events between New Guinea and Australia. Oxyuranus and Pseudonaja form a robust clade. The small burrowing taxa form two separate clades, one consisting of Vermicella and Neelaps calanotus, and the other including Simoselaps, Brachyurophis and Neelaps bimaculatus. The viviparous terrestrial elapids form three separate groups: Acanthophis, the Rhinoplocephalus group and the Notechis-Hemiaspis group. True sea snakes (Hydrophiini) are robustly united with the Notechis-Hemiaspis group. Many of the retrieved groupings are consistent with previous molecular and morphological analyses, but the polyphyly of the viviparous and burrowing groups, and of Neelaps, are novel results. Bayesian relaxed clock analyses indicate very recent divergences: the approximately 160 species of the core Australian radiation (including sea snakes) arose within the last 10 Myr, with most inter-generic splits dating to between 10 and 6 Ma. The Hydrophis sea snake lineage is an exceptionally rapid radiation, with > 40 species evolving within the last 5 Myr.
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Affiliation(s)
- K L Sanders
- School of Earth and Environmental Sciences, University of Adelaide, Adelaide, Australia.
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Abstract
A limiting factor in many molecular dating studies is shortage of reliable calibrations. Current methods for choosing calibrations (e.g. cross-validation) treat them as either correct or incorrect, whereas calibrations probably lie on a continuum from highly accurate to very poor. Bayesian relaxed clock analysis permits inclusion of numerous candidate calibrations as priors: provided most calibrations are reliable, the model appropriate and the data informative, the accuracy of each calibration prior can be evaluated. If a calibration is accurate, then the analysis will support the prior so that the posterior estimate reflects the prior; if a calibration is poor, the posterior will be forced away from the prior. We use this approach to test two fossil dates recently proposed as standard calibrations within vertebrates. The proposed bird-crocodile calibration (approx. 247Myr ago) appears to be accurate, but the proposed bird-lizard calibration (approx. 255Myr ago) is substantially too recent.
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Affiliation(s)
- Kate L Sanders
- School of Earth and Environmental Sciences, University of Adelaide, Darling Building, Adelaide, Australia 5005.
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Sanders KL, Lee MSY. Molecular evidence for a rapid late-Miocene radiation of Australasian venomous snakes (Elapidae, Colubroidea). Mol Phylogenet Evol 2007; 46:1165-73. [PMID: 18222097 DOI: 10.1016/j.ympev.2007.11.013] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Revised: 10/17/2007] [Accepted: 11/21/2007] [Indexed: 11/25/2022]
Affiliation(s)
- Kate L Sanders
- Darling Building, School of Earth and Environmental Sciences, University of Adelaide, Adelaide 5005, Australia.
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Sanders KL, Malhotra A, Thorpe RS. Ecological diversification in a group of Indomalayan pitvipers (Trimeresurus): convergence in taxonomically important traits has implications for species identification. J Evol Biol 2004; 17:721-31. [PMID: 15271071 DOI: 10.1111/j.1420-9101.2004.00735.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We analyse molecular and phenotypic evolution in a group of taxonomically problematic Indomalayan pitvipers, the Trimeresurus sumatranus group. Mitochondrial DNA sequencing provides a well-resolved phylogeny, with each species representing a distinct lineage. Multivariate morphological analysis reveals a high level of phenotypic differentiation, which is congruent between the sexes but does not reflect phylogenetic history. An adaptive explanation for the observed pattern of differentiation is supported by independent contrasts analysis, which shows significant correlations between current ecology and the characters that most account for the variation between taxa, including those that are presently used to identify the species. Reduced precipitation and altitude, and increased temperature, are correlated with higher numbers of scales on the head, body and tail. It is hypothesized that scale number plays an important role in heat and water exchange by influencing the area of exposed of interstitial skin, and that colour pattern variation reflects selection pressures involving camouflage and thermoregulation. Ecological convergence in traits used for classification is found to have important implications for species identification where taxa are distributed over varying environments.
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Affiliation(s)
- K L Sanders
- School of Biological Sciences, University of Wales, Bangor, Gwynedd, UK
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