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Moysiuk J, Caron JB. A three-eyed radiodont with fossilized neuroanatomy informs the origin of the arthropod head and segmentation. Curr Biol 2022; 32:3302-3316.e2. [PMID: 35809569 DOI: 10.1016/j.cub.2022.06.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 04/19/2022] [Accepted: 06/09/2022] [Indexed: 01/04/2023]
Abstract
In addition to being among the most iconic and bizarre-looking Cambrian animals, radiodonts are a group that offers key insight into the acquisition of the arthropod body plan by virtue of their phylogenetic divergence prior to all living members of the phylum. Nonetheless, radiodont fossils are rare and often fragmentary, and contentions over their interpretation have hindered resolution of important evolutionary conundrums. Here, we describe 268 specimens of Stanleycaris hirpex from the Cambrian Burgess Shale, including many exceptionally preserved whole-body specimens, informing the most complete reconstruction of a radiodont to date. The trunk region of Stanleycaris has up to 17 segments plus two pairs of filiform caudal blades. The recognition of dorsal sclerotic segmentation of the trunk cuticle and putative unganglionated nerve cords provides new insight into the relative timing of acquisition of segmental traits, the epitome of the arthropod body plan. In addition to the pair of stalked lateral eyes, the short head unexpectedly bears a large median eye situated behind a preocular sclerite on an anteriorly projecting head lobe. Upon re-evaluation, similar median eyes can be identified in other Cambrian panarthropods demonstrating a deep evolutionary continuity. The exquisitely preserved brain of Stanleycaris is consistent with the hypothesized deutocerebral innervation of the frontal appendages, reconciling neuroanatomical evidence with external morphology in support of an ancestrally bipartite head and brain for arthropods. We propose that the integration of this bipartite head prior to the acquisition of most segmental characters exclusively in the arthropod trunk may help explain its developmental differentiation.
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Affiliation(s)
- Joseph Moysiuk
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada; Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, ON M5S 2C6, Canada.
| | - Jean-Bernard Caron
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada; Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, ON M5S 2C6, Canada; Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, ON M5S 3B1, Canada.
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Wegener C, Chen J. Allatostatin A Signalling: Progress and New Challenges From a Paradigmatic Pleiotropic Invertebrate Neuropeptide Family. Front Physiol 2022; 13:920529. [PMID: 35812311 PMCID: PMC9263205 DOI: 10.3389/fphys.2022.920529] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 05/31/2022] [Indexed: 02/02/2023] Open
Abstract
Neuropeptides have gained broad attraction in insect neuroscience and physiology, as new genetic tools are increasingly uncovering their wide-ranging pleiotropic functions with high cellular resolution. Allatostatin A (AstA) peptides constitute one of the best studied insect neuropeptide families. In insects and other panarthropods, AstA peptides qualify as brain-gut peptides and have regained attention with the discovery of their role in regulating feeding, growth, activity/sleep and learning. AstA receptor homologs are found throughout the protostomia and group with vertebrate somatostatin/galanin/kisspeptin receptors. In this review, we summarise the current knowledge on the evolution and the pleiotropic and cell-specific non-allatostatic functions of AstA. We speculate about the core functions of AstA signalling, and derive open questions and challengesfor future research on AstA and invertebrate neuropeptides in general.
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Affiliation(s)
- Christian Wegener
- Neurobiology and Genetics, Würzburg Insect Research, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg, Germany
- *Correspondence: Christian Wegener,
| | - Jiangtian Chen
- Department of Ecology, Evolution and Organismal Biology, Brown University, Providence, RI, United States
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Martin C, Jahn H, Klein M, Hammel JU, Stevenson PA, Homberg U, Mayer G. The velvet worm brain unveils homologies and evolutionary novelties across panarthropods. BMC Biol 2022; 20:26. [PMID: 35073910 PMCID: PMC9136957 DOI: 10.1186/s12915-021-01196-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 11/16/2021] [Indexed: 11/10/2022] Open
Abstract
Background The evolution of the brain and its major neuropils in Panarthropoda (comprising Arthropoda, Tardigrada and Onychophora) remains enigmatic. As one of the closest relatives of arthropods, onychophorans are regarded as indispensable for a broad understanding of the evolution of panarthropod organ systems, including the brain, whose anatomical and functional organisation is often used to gain insights into evolutionary relations. However, while numerous recent studies have clarified the organisation of many arthropod nervous systems, a detailed investigation of the onychophoran brain with current state-of-the-art approaches is lacking, and further inconsistencies in nomenclature and interpretation hamper its understanding. To clarify the origins and homology of cerebral structures across panarthropods, we analysed the brain architecture in the onychophoran Euperipatoides rowelli by combining X-ray micro-computed tomography, histology, immunohistochemistry, confocal microscopy, and three-dimensional reconstruction. Results Here, we use this detailed information to generate a consistent glossary for neuroanatomical studies of Onychophora. In addition, we report novel cerebral structures, provide novel details on previously known brain areas, and characterise further structures and neuropils in order to improve the reproducibility of neuroanatomical observations. Our findings support homology of mushroom bodies and central bodies in onychophorans and arthropods. Their antennal nerve cords and olfactory lobes most likely evolved independently. In contrast to previous reports, we found no evidence for second-order visual neuropils, or a frontal ganglion in the velvet worm brain. Conclusion We imaged the velvet worm nervous system at an unprecedented level of detail and compiled a comprehensive glossary of known and previously uncharacterised neuroanatomical structures to provide an in-depth characterisation of the onychophoran brain architecture. We expect that our data will improve the reproducibility and comparability of future neuroanatomical studies. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-01196-w.
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Herranz M, Park T, Di Domenico M, Leander BS, Sørensen MV, Worsaae K. Revisiting kinorhynch segmentation: variation of segmental patterns in the nervous system of three aberrant species. Front Zool 2021; 18:54. [PMID: 34674731 PMCID: PMC8529749 DOI: 10.1186/s12983-021-00438-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 10/05/2021] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Kinorhynch segmentation differs from the patterns found in Chordata, Arthropoda and Annelida which have coeloms and circulatory systems. Due to these differences and their obsolete status as 'Aschelminthes', the microscopic kinorhynchs are often not acknowledged as segmented bilaterians. Yet, morphological studies have shown a conserved segmental arrangement of ectodermal and mesodermal organ systems with spatial correspondence along the anterior-posterior axis. However, a few aberrant kinorhynch lineages present a worm-like body plan with thin cuticle and less distinct segmentation, and thus their study may aid to shed new light on the evolution of segmental patterns within Kinorhyncha. RESULTS Here we found the nervous system in the aberrant Cateria styx and Franciscideres kalenesos to be clearly segmental, and similar to those of non-aberrant kinorhynchs; hereby not mirroring their otherwise aberrant and posteriorly shifted myoanatomy. In Zelinkaderes yong, however, the segmental arrangement of the nervous system is also shifted posteriorly and misaligned with respect to the cuticular segmentation. CONCLUSIONS The morphological disparity together with the distant phylogenetic positions of F. kalenesos, C. styx and Z. yong support a convergent origin of aberrant appearances and segmental mismatches within Kinorhyncha.
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Affiliation(s)
- Maria Herranz
- Department of Biology, University of Copenhagen, Copenhagen, Denmark.
- Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
| | - Taeseo Park
- National Institute of Biological Resources, Incheon, South Korea
| | - Maikon Di Domenico
- Centro de Estudos do Mar, Universidade Federal do Paraná, Pontal do Paraná, Brazil
| | - Brian S Leander
- Departments of Zoology and Botany, University of British Columbia, Vancouver, Canada
| | - Martin V Sørensen
- Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark
| | - Katrine Worsaae
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
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Gross V, Epple L, Mayer G. Organization of the central nervous system and innervation of cephalic sensory structures in the water bear Echiniscus testudo (Tardigrada: Heterotardigrada) revisited. J Morphol 2021; 282:1298-1312. [PMID: 34129245 DOI: 10.1002/jmor.21386] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 05/22/2021] [Accepted: 06/13/2021] [Indexed: 11/09/2022]
Abstract
The tardigrade brain has been the topic of several neuroanatomical studies, as it is key to understanding the evolution of the central nervous systems in Panarthropoda (Tardigrada + Onychophora + Arthropoda). The gross morphology of the brain seems to be well conserved across tardigrades despite often disparate morphologies of their heads and cephalic sensory structures. As such, the general shape of the brain and its major connections to the rest of the central nervous system have been mapped out already by early tardigradologists. Despite subsequent investigations primarily based on transmission electron microscopy or immunohistochemistry, characterization of the different regions of the tardigrade brain has progressed relatively slowly and open questions remain. In an attempt to improve our understanding of different brain regions, we reinvestigated the central nervous system of the heterotardigrade Echiniscus testudo using anti-synapsin and anti-acetylated α-tubulin immunohistochemistry in order to visualize the number and position of tracts, commissures, and neuropils. Our data revealed five major synapsin-immunoreactive domains along the body: a large unitary, horseshoe-shaped neuropil in the head and four neuropils in the trunk ganglia, supporting the hypothesis that the dorsal brain is serially homologous with the ventral trunk ganglia. At the same time, the pattern of anti-synapsin and anti-tubulin immunoreactivity differs between the ganglia, adding to the existing evidence that each of the four trunk ganglia is unique in its morphology. Anti-tubulin labeling further revealed two commissures within the central brain neuropil, one of which is forked, and additional sets of extracerebral cephalic commissures associated with the stomodeal nervous system and the ventral cell cluster. Furthermore, our results showing the innervation of each of the cephalic sensilla in E. testudo support the homology of subsets of these structures with the sensory fields of eutardigrades.
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Affiliation(s)
- Vladimir Gross
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
| | - Lisa Epple
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
| | - Georg Mayer
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
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Herranz M, Sørensen MV, Park T, Leander BS, Worsaae K. Insights into mud dragon morphology (Kinorhyncha, Allomalorhagida): myoanatomy and neuroanatomy of Dracoderes abei and Pycnophyes ilyocryptus. ORG DIVERS EVOL 2020. [DOI: 10.1007/s13127-020-00447-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Oliveira IDS, Kumerics A, Jahn H, Müller M, Pfeiffer F, Mayer G. Functional morphology of a lobopod: case study of an onychophoran leg. ROYAL SOCIETY OPEN SCIENCE 2019; 6:191200. [PMID: 31824728 PMCID: PMC6837196 DOI: 10.1098/rsos.191200] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 09/09/2019] [Indexed: 05/08/2023]
Abstract
Segmental, paired locomotory appendages are a characteristic feature of Panarthropoda-a diversified clade of moulting animals that includes onychophorans (velvet worms), tardigrades (water bears) and arthropods. While arthropods acquired a sclerotized exoskeleton and articulated limbs, onychophorans and tardigrades possess a soft body and unjointed limbs called lobopods, which they inherited from Cambrian lobopodians. To date, the origin and ancestral structure of the lobopods and their transformation into the jointed appendages are all poorly understood. We therefore combined high-resolution computed tomography with high-speed camera recordings to characterize the functional anatomy of a trunk lobopod from the onychophoran Euperipatoides rowelli. Three-dimensional reconstruction of the complete set of muscles and muscle fibres as well as non-muscular structures revealed the spatial relationship and relative volumes of the muscular, excretory, circulatory and nervous systems within the leg. Locomotory movements of individual lobopods of E. rowelli proved far more diverse than previously thought and might be governed by a complex interplay of 15 muscles, including one promotor, one remotor, one levator, one retractor, two depressors, two rotators, one flexor and two constrictors as well as muscles for stabilization and haemolymph control. We discuss the implications of our findings for understanding the evolution of locomotion in panarthropods.
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Affiliation(s)
- Ivo de Sena Oliveira
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
- Departamento de Zoologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Andreas Kumerics
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
| | - Henry Jahn
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
| | - Mark Müller
- Chair of Biomedical Physics, Department of Physics and Munich School of Bioengineering, Technical University of Munich, Garching, Germany
| | - Franz Pfeiffer
- Chair of Biomedical Physics, Department of Physics and Munich School of Bioengineering, Technical University of Munich, Garching, Germany
- Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar, Technical University of Munich, 81675 München, Germany
| | - Georg Mayer
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
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Tetsch L. Auf den Leim gegangen. CHEM UNSERER ZEIT 2019. [DOI: 10.1002/ciuz.201980040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Smith FW, Cumming M, Goldstein B. Analyses of nervous system patterning genes in the tardigrade Hypsibius exemplaris illuminate the evolution of panarthropod brains. EvoDevo 2018; 9:19. [PMID: 30069303 PMCID: PMC6065069 DOI: 10.1186/s13227-018-0106-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 07/16/2018] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Both euarthropods and vertebrates have tripartite brains. Several orthologous genes are expressed in similar regionalized patterns during brain development in both vertebrates and euarthropods. These similarities have been used to support direct homology of the tripartite brains of vertebrates and euarthropods. If the tripartite brains of vertebrates and euarthropods are homologous, then one would expect other taxa to share this structure. More generally, examination of other taxa can help in tracing the evolutionary history of brain structures. Tardigrades are an interesting lineage on which to test this hypothesis because they are closely related to euarthropods, and whether they have a tripartite brain or unipartite brain has recently been a focus of debate. RESULTS We tested this hypothesis by analyzing the expression patterns of six3, orthodenticle, pax6, unplugged, and pax2/5/8 during brain development in the tardigrade Hypsibius exemplaris-formerly misidentified as Hypsibius dujardini. These genes were expressed in a staggered anteroposterior order in H. exemplaris, similar to what has been reported for mice and flies. However, only six3, orthodenticle, and pax6 were expressed in the developing brain. Unplugged was expressed broadly throughout the trunk and posterior head, before the appearance of the nervous system. Pax2/5/8 was expressed in the developing central and peripheral nervous system in the trunk. CONCLUSION Our results buttress the conclusion of our previous study of Hox genes-that the brain of tardigrades is only homologous to the protocerebrum of euarthropods. They support a model based on fossil evidence that the last common ancestor of tardigrades and euarthropods possessed a unipartite brain. Our results are inconsistent with the hypothesis that the tripartite brain of euarthropods is directly homologous to the tripartite brain of vertebrates.
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Affiliation(s)
- Frank W. Smith
- Biology Department, University of North Florida, Jacksonville, FL USA
- Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC USA
| | - Mandy Cumming
- Biology Department, University of North Florida, Jacksonville, FL USA
| | - Bob Goldstein
- Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC USA
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Treffkorn S, Kahnke L, Hering L, Mayer G. Expression of NK cluster genes in the onychophoran Euperipatoides rowelli: implications for the evolution of NK family genes in nephrozoans. EvoDevo 2018; 9:17. [PMID: 30026904 PMCID: PMC6050708 DOI: 10.1186/s13227-018-0105-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 07/06/2018] [Indexed: 02/05/2023] Open
Abstract
Background Understanding the evolution and development of morphological traits of the last common bilaterian ancestor is a major goal of the evo-devo discipline. The reconstruction of this "urbilaterian" is mainly based on comparative studies of common molecular patterning mechanisms in recent model organisms. The NK homeobox genes are key players in many of these molecular pathways, including processes regulating mesoderm, heart and neural development. Shared features seen in the expression patterns of NK genes have been used to determine the ancestral bilaterian characters. However, the commonly used model organisms provide only a limited view on the evolution of these molecular pathways. To further investigate the ancestral roles of NK cluster genes, we analyzed their expression patterns in the onychophoran Euperipatoides rowelli. Results We identified nine transcripts of NK cluster genes in E. rowelli, including single copies of NK1, NK3, NK4, NK5, Msx, Lbx and Tlx, and two copies of NK6. All of these genes except for NK6.1 and NK6.2 are expressed in different mesodermal organs and tissues in embryos of E. rowelli, including the anlagen of somatic musculature and the heart. Furthermore, we found distinct expression patterns of NK3, NK5, NK6, Lbx and Msx in the developing nervous system. The same holds true for the NKL gene NK2.2, which does not belong to the NK cluster but is a related gene playing a role in neural patterning. Surprisingly, NK1, Msx and Lbx are additionally expressed in a segment polarity-like pattern early in development-a feature that has been otherwise reported only from annelids. Conclusion Our results indicate that the NK cluster genes were involved in mesoderm and neural development in the last common ancestor of bilaterians or at least nephrozoans (i.e., bilaterians to the exclusion of xenacoelomorphs). By comparing our data from an onychophoran to those from other bilaterians, we critically review the hypothesis of a complex "urbilaterian" with a segmented body, a pulsatile organ or heart, and a condensed mediolaterally patterned nerve cord.
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Affiliation(s)
- Sandra Treffkorn
- Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany
| | - Laura Kahnke
- Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany
| | - Lars Hering
- Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany
| | - Georg Mayer
- Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany
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Jahn H, Oliveira IDES, Gross V, Martin C, Hipp A, Mayer G, Hammel JU. Evaluation of contrasting techniques for X-ray imaging of velvet worms (Onychophora). J Microsc 2018; 270:343-358. [PMID: 29469207 DOI: 10.1111/jmi.12688] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 12/20/2017] [Accepted: 01/29/2018] [Indexed: 01/04/2023]
Abstract
Non-invasive imaging techniques like X-ray computed tomography have become very popular in zoology, as they allow for simultaneous imaging of the internal and external morphology of organisms. Nevertheless, the effect of different staining approaches required for this method on samples lacking mineralized tissues, such as soft-bodied invertebrates, remains understudied. Herein, we used synchrotron radiation-based X-ray micro-computed tomography to compare the effects of commonly used contrasting approaches on onychophorans - soft-bodied invertebrates important for studying animal evolution. Representatives of Euperipatoides rowelli were stained with osmium tetroxide (vapour or solution), ruthenium red, phosphotungstic acid, or iodine. Unstained specimens were imaged using both standard attenuation-based and differential phase-contrast setups to simulate analyses with museum material. Our comparative qualitative analyses of several tissue types demonstrate that osmium tetroxide provides the best overall tissue contrast in onychophorans, whereas the remaining staining agents rather favour the visualisation of specific tissues and/or structures. Quantitative analyses using signal-to-noise ratio measurements show that the level of image noise may vary according to the staining agent and scanning medium selected. Furthermore, box-and-whisker plots revealed substantial overlap in grey values among structures in all datasets, suggesting that a combination of semiautomatic and manual segmentation of structures is required for comprehensive 3D reconstructions of Onychophora, irrespective of the approach selected. Our results show that X-ray micro-computed tomography is a promising technique for studying onychophorans and, despite the benefits and disadvantages of different staining agents for specific tissues/structures, this method retrieves informative data that may eventually help address evolutionary questions long associated with Onychophora.
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Affiliation(s)
- Henry Jahn
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
| | - Ivo DE Sena Oliveira
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany.,Departamento de Zoologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Vladimir Gross
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
| | - Christine Martin
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
| | - Alexander Hipp
- Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany
| | - Georg Mayer
- Department of Zoology, Institute of Biology, University of Kassel, Kassel, Germany
| | - Jörg U Hammel
- Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany.,Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-University of Jena, Jena, Germany
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Giribet G, Edgecombe GD. Current Understanding of Ecdysozoa and its Internal Phylogenetic Relationships. Integr Comp Biol 2017; 57:455-466. [DOI: 10.1093/icb/icx072] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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13
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Yoshida Y, Koutsovoulos G, Laetsch DR, Stevens L, Kumar S, Horikawa DD, Ishino K, Komine S, Kunieda T, Tomita M, Blaxter M, Arakawa K. Comparative genomics of the tardigrades Hypsibius dujardini and Ramazzottius varieornatus. PLoS Biol 2017; 15:e2002266. [PMID: 28749982 PMCID: PMC5531438 DOI: 10.1371/journal.pbio.2002266] [Citation(s) in RCA: 128] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 06/23/2017] [Indexed: 01/27/2023] Open
Abstract
Tardigrada, a phylum of meiofaunal organisms, have been at the center of discussions of the evolution of Metazoa, the biology of survival in extreme environments, and the role of horizontal gene transfer in animal evolution. Tardigrada are placed as sisters to Arthropoda and Onychophora (velvet worms) in the superphylum Panarthropoda by morphological analyses, but many molecular phylogenies fail to recover this relationship. This tension between molecular and morphological understanding may be very revealing of the mode and patterns of evolution of major groups. Limnoterrestrial tardigrades display extreme cryptobiotic abilities, including anhydrobiosis and cryobiosis, as do bdelloid rotifers, nematodes, and other animals of the water film. These extremophile behaviors challenge understanding of normal, aqueous physiology: how does a multicellular organism avoid lethal cellular collapse in the absence of liquid water? Meiofaunal species have been reported to have elevated levels of horizontal gene transfer (HGT) events, but how important this is in evolution, and particularly in the evolution of extremophile physiology, is unclear. To address these questions, we resequenced and reassembled the genome of H. dujardini, a limnoterrestrial tardigrade that can undergo anhydrobiosis only after extensive pre-exposure to drying conditions, and compared it to the genome of R. varieornatus, a related species with tolerance to rapid desiccation. The 2 species had contrasting gene expression responses to anhydrobiosis, with major transcriptional change in H. dujardini but limited regulation in R. varieornatus. We identified few horizontally transferred genes, but some of these were shown to be involved in entry into anhydrobiosis. Whole-genome molecular phylogenies supported a Tardigrada+Nematoda relationship over Tardigrada+Arthropoda, but rare genomic changes tended to support Tardigrada+Arthropoda.
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Affiliation(s)
- Yuki Yoshida
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Kanagawa, Japan
| | - Georgios Koutsovoulos
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Dominik R. Laetsch
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
- The James Hutton Institute, Dundee, United Kingdom
| | - Lewis Stevens
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Sujai Kumar
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Daiki D. Horikawa
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Kanagawa, Japan
| | - Kyoko Ishino
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
| | - Shiori Komine
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
| | - Takekazu Kunieda
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Masaru Tomita
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Kanagawa, Japan
| | - Mark Blaxter
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Kazuharu Arakawa
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Kanagawa, Japan
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Martin C, Gross V, Hering L, Tepper B, Jahn H, de Sena Oliveira I, Stevenson PA, Mayer G. The nervous and visual systems of onychophorans and tardigrades: learning about arthropod evolution from their closest relatives. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2017; 203:565-590. [DOI: 10.1007/s00359-017-1186-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/02/2017] [Accepted: 05/29/2017] [Indexed: 12/19/2022]
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Minelli A. Introduction: The evolution of segmentation. ARTHROPOD STRUCTURE & DEVELOPMENT 2017; 46:323-327. [PMID: 28235577 DOI: 10.1016/j.asd.2017.02.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 02/20/2017] [Accepted: 02/20/2017] [Indexed: 06/06/2023]
Affiliation(s)
- Alessandro Minelli
- Department of Biology, University of Padova, Via Ugo Bassi, 58 B, I 35131 Padova, Italy.
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