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Skull ecomorphological variation of narwhals (Monodon monoceros, Linnaeus 1758) and belugas (Delphinapterus leucas, Pallas 1776) reveals phenotype of their hybrids. PLoS One 2022; 17:e0273122. [PMID: 35960760 PMCID: PMC9374245 DOI: 10.1371/journal.pone.0273122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 08/03/2022] [Indexed: 11/19/2022] Open
Abstract
Narwhals and belugas are toothed whales belonging to the Monodontidae. Belugas have a circumpolar Arctic and sub-Artic distribution while narwhals are restricted to the Atlantic Arctic. Their geographical ranges overlap during winter migrations in the Baffin Bay area (Canada/West Greenland) and successful interbreeding may occur. Here, we employed geometric morphometrics on museum specimens to explore the cranium and mandible morphology of a known hybrid (NHMD MCE 1356) and the cranium morphology of a putative hybrid (NHMD 1963.44.1.4) relative to skull morphological variation in the parental species. Specifically, we used 3D models of skulls from 69 belugas, 86 narwhals, and the two known/putative hybrids and 2D left hemi-mandibles from 20 belugas, 64 narwhals and the known hybrid. Skull shape analyses allowed clear discrimination between species. Narwhals are characterised by a relatively short rostrum and wide neurocranium while belugas show a more elongated and narrower cranium. Sexual size dimorphism was detected in narwhals, with males larger than females, but no sexual shape dimorphism was detected in either species (excluding presence/absence of tusks in narwhals). Morphological skull variation was also dependent on different allometric slopes between species and sexes in narwhals. Our analyses showed that the cranium of the known hybrid was phenotypically close to belugas but its 2D hemi-mandible had a narwhal shape and size morphology. Both cranium and mandible were strongly correlated, with the pattern of covariation being similar to belugas. The putative hybrid was a pure male narwhal with extruded teeth. Comparison of genomic DNA supported this result, and stable carbon and nitrogen isotope values suggested that the putative hybrid had a more benthic foraging strategy compared to narwhals. This work demonstrates that although the known hybrid could be discriminated from narwhals and belugas, detection of its affinities with these parental species was dependent on the part of the skull analysed.
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Brookwell R, Finlayson K, van de Merwe JP. The Karyotype of Blainville's Beaked Whale, Mesoplodon densirostris. Cytogenet Genome Res 2020; 160:698-703. [PMID: 33207347 DOI: 10.1159/000511730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 09/21/2020] [Indexed: 11/19/2022] Open
Abstract
The karyotype of the Odontocete whale, Mesoplodon densirostris, has not been previously reported. The chromosome number is determined to be 2n = 42, and the karyotype is presented using G-, C-, and nucleolar organizer region (NOR) banding. The findings include NOR regions on 2 chromosomes, regions of heterochromatic variation, a large block of heterochromatin on the X chromosome, and a relatively large Y chromosome. The karyotype is compared to published karyograms of 2 other species of Mesoplodon.
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Affiliation(s)
- Ross Brookwell
- Cytogenetics Department, Sullivan Nicolaides Pathology, Bowen Hills, Queensland, Australia,
| | - Kimberly Finlayson
- Australian Rivers Institute, Griffith University Gold Coast, Southport, Queensland, Australia
| | - Jason P van de Merwe
- Australian Rivers Institute, Griffith University Gold Coast, Southport, Queensland, Australia
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Antoniou A, Frantzis A, Alexiadou P, Paschou N, Poulakakis N. Evidence of introgressive hybridization between Stenella coeruleoalba and Delphinus delphis in the Greek Seas. Mol Phylogenet Evol 2018; 129:325-337. [PMID: 30218775 DOI: 10.1016/j.ympev.2018.09.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 05/29/2018] [Accepted: 09/08/2018] [Indexed: 10/28/2022]
Abstract
Natural interspecific hybridization might be more important for the evolutionary history and speciation of animals than previously thought, considering several demographic and life history traits as well as habitat disturbance as factors that promote it. In this aspect, cetaceans comprise an interesting case in which the occurrence of sympatric species in mixed associations provides excellent opportunities for interspecific sexual interaction and the potential for hybridization. Here, we present evidence of natural hybridization for two cetacean species commonly occurring in the Greek Seas (Stenella coeruleoalba and Delphinus delphis), which naturally overlap in the Gulf of Corinth by analyzing highly resolving microsatellite DNA markers and mitochondrial DNA sequences in skin samples from 45 individuals of S. coeruleoalba, 12 D. delphis and three intermediate morphs. Employing several phylogenetic and population genetic approaches, we found 15 individuals that are potential hybrids including the three intermediate morphs, verifying the occurrence of natural hybridization between species of different genera. Their hybrids are fertile and able to reproduce not only with the other hybrids but also with each of the two-parental species. However, current evidence does not allow firm conclusions whether hybridization might constitute a step towards the generation of a new species and/or the swan song of an already existing species (i.e., D. delphis). Given that the focal species form mixed pods in several areas of Mediterranean, this study is an excellent opportunity to understand the mechanisms leading to hybridization in the context of gene flow and urges for the evaluation of the genetic status of common dolphins in the Mediterranean.
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Affiliation(s)
- Aglaia Antoniou
- Institute of Marine Biology, Biotechnology and Aquaculture (IMBBC), Hellenic Centre for Marine Research, Gournes Pediados, P.O. Box 2214, 71003 Irakleio, Crete, Greece.
| | - Alexandros Frantzis
- Pelagos Cetacean Research Institute, Terpsichoris 21, 16671 Vouliagmeni, Greece
| | - Paraskevi Alexiadou
- Pelagos Cetacean Research Institute, Terpsichoris 21, 16671 Vouliagmeni, Greece
| | - Nefeli Paschou
- Department of Biology, School of Sciences and Engineering, University of Crete, Vasilika Vouton, Gr-71300 Heraklion, Crete, Greece; Natural History Museum of Crete, School of Sciences and Engineering, University of Crete, Knossos Av., GR-71409 Heraklion, Crete, Greece
| | - Nikos Poulakakis
- Department of Biology, School of Sciences and Engineering, University of Crete, Vasilika Vouton, Gr-71300 Heraklion, Crete, Greece; Natural History Museum of Crete, School of Sciences and Engineering, University of Crete, Knossos Av., GR-71409 Heraklion, Crete, Greece
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Kurihara N, Tajima Y, Yamada TK, Matsuda A, Matsuishi T. Description of the karyotypes of Stejneger's beaked whale (Mesoplodon stejnegeri) and Hubbs' beaked whale (M. carlhubbsi). Genet Mol Biol 2017; 40:803-807. [PMID: 28981559 PMCID: PMC5738608 DOI: 10.1590/1678-4685-gmb-2016-0284] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 02/06/2017] [Indexed: 11/21/2022] Open
Abstract
The genus Mesoplodon (Cetacea: Odontoceti: Ziphiidae) is one of
the few cetacean genera with the karyotype 2n = 42. The 2n = 42 karyotype of
M. europaeus and M. carlhubbsi is largely
consistent with the general cetacean karyotype 2n = 44, although other 2n = 42
karyotypes do not exhibit clear homologies with the general cetacean karyotype.
Therefore, the chromosomes of Mesoplodon species may be the key
to understanding cetacean karyological evolution. In the present study, the male
karyotypes of M. stejnegeri and M. carlhubbsi
were examined. In both species, the diploid number of the male karyotype was 42.
Both species had the following characteristics: 1) a huge subtelocentric X
chromosome with a large C-block; 2) a small metacentric Y chromosome; 3)
nucleolus organizer regions (NORs) in the terminal regions of a large autosome
and one or two small metacentric autosomes; 4) small metacentric autosomes; 5)
large submetacentric and subtelocentric autosomes; 6) less accumulated
C-heterochromatin in the centromeric region; and 7) heteromorphism in
C-heterochromatin accumulation between homologues. Characteristics 1 and 3 are
peculiar to only the karyotypes of Mesoplodon species, whereas
characteristics 4, 5, 6, and 7 are also found in the species with the general
cetacean karyotype 2n = 44.
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Affiliation(s)
- Nozomi Kurihara
- Faculty of Agriculture, Utsunomiya University, Utsunomiya-shi, Tochigi prefecture, Japan
| | - Yuko Tajima
- Department of Zoology, National Museum of Nature and Science, Tsukuba-shi, Ibaraki prefecture, Japan
| | - Tadasu K Yamada
- Department of Zoology, National Museum of Nature and Science, Tsukuba-shi, Ibaraki prefecture, Japan
| | - Ayaka Matsuda
- Graduate School of Fisheries Sciences, Hokkaido University, Hakodate-shi, Hokkaido, Japan
| | - Takashi Matsuishi
- Faculty of Fisheries Science, Hokkaido University, Hakodate-shi, Hokkaido, Japan
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Crossman CA, Taylor EB, Barrett-Lennard LG. Hybridization in the Cetacea: widespread occurrence and associated morphological, behavioral, and ecological factors. Ecol Evol 2016; 6:1293-303. [PMID: 27087919 PMCID: PMC4775523 DOI: 10.1002/ece3.1913] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 12/02/2015] [Accepted: 12/03/2015] [Indexed: 11/21/2022] Open
Abstract
Hybridization has been documented in a many different pairs of cetacean species both in captivity and in the wild. The widespread occurrence of hybridization indicates that postmating barriers to interbreeding are incomplete within the order Cetacea, and therefore raises questions about how species integrity is maintained in the face of interspecific (and often intergeneric) gene flow. We examined hybridization across the order Cetacea (oceanic species included: N = 78; species with 44 chromosomes included: N = 52) to test for associations between the occurrence of hybridization and similarity across 13 ecological, morphological and behavioral traits in hybridizing vs. non‐hybridizing species pairs. We found that species pairs that share a greater number of traits had a higher propensity to hybridize than pairs of species that did not. This trend was driven by behavioral and morphological traits such as vocalization frequency and body size. Together our findings suggest the importance of divergent selection on morphological and behavioral traits within sympatric species in constraining opportunities for hybridization and preventing the collapse of parental species.
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Affiliation(s)
- Carla A Crossman
- Marine Mammal Research Program Coastal Ocean Research Institute Vancouver Aquarium Marine Science Centre Vancouver British Columbia Canada; Department of Zoology University of British Columbia Vancouver British Columbia Canada
| | - Eric B Taylor
- Department of Zoology University of British Columbia Vancouver British Columbia Canada; Biodiversity Research Centre, and Beaty Biodiversity Museum University of British Columbia Vancouver British Columbia Canada
| | - Lance G Barrett-Lennard
- Marine Mammal Research Program Coastal Ocean Research Institute Vancouver Aquarium Marine Science Centre Vancouver British Columbia Canada; Department of Zoology University of British Columbia Vancouver British Columbia Canada
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Molecular cytogenetic characterization of the Amazon River dolphin Inia geoffrensis. Genetica 2012; 140:307-15. [PMID: 23010983 DOI: 10.1007/s10709-012-9680-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 09/08/2012] [Indexed: 10/27/2022]
Abstract
Classical and molecular cytogenetic (18S rDNA, telomeric sequence, and LINE-1 retrotransposon probes) studies were carried out to contribute to an understanding of the organization of repeated DNA elements in the Amazon River dolphin (boto, Inia geoffrensis). Twenty-seven specimens were examined, each presenting 2n = 44 chromosomes, the karyotype formula 12m + 14sm + 6st + 10t + XX/XY, and fundamental number (FN) = 74. C-positive heterochromatin was observed in terminal and interstitial positions, with the occurrence of polymorphism. Interstitial telomeric sequences were not observed. The nucleolar organizer region (NOR) was located at a single site on a smallest autosomal pair. LINE-1 was preferentially distributed in the euchromatin regions, with the greatest accumulation on the X chromosome. Although the karyotype structure in cetaceans is considered to be conserved, the boto karyotype demonstrated significant variations in its formula, heterochromatin distribution, and the location of the NOR compared to other cetacean species. These results contribute to knowledge of the chromosome organization in boto and to a better understanding of karyoevolution in cetaceans.
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