Revisiting the Karyotypes of Alligators and Caimans (Crocodylia, Alligatoridae) after a Half-Century Delay: Bridging the Gap in the Chromosomal Evolution of Reptiles
Vanessa C. S. Oliveira,
Marie Altmanová,
Patrik F. Viana,
Tariq Ezaz,
Luiz A. C. Bertollo,
Petr Ráb,
Thomas Liehr,
Ahmed Al-Rikabi,
Eliana Feldberg,
Terumi Hatanaka,
Sebastian Scholz,
Alexander Meurer,
Marcelo de Bello Cioffi
Affiliations
Vanessa C. S. Oliveira
Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos 13565-905, Brazil
Marie Altmanová
Department of Ecology, Faculty of Science, Charles University, 12844 Prague, Czech Republic
Patrik F. Viana
Laboratório de Genética Animal, Coordenação de Biodiversidade, Instituto Nacional de Pesquisas da Amazônia, Manaus 69083-000, Brazil
Tariq Ezaz
Institute for Applied Ecology, Faculty of Science and Technology, University of Canberra, Bruce, ACT 2617, Australia
Luiz A. C. Bertollo
Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos 13565-905, Brazil
Petr Ráb
Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, 27721 Liběchov, Czech Republic
Thomas Liehr
Institute of Human Genetics, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany
Ahmed Al-Rikabi
Institute of Human Genetics, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany
Eliana Feldberg
Laboratório de Genética Animal, Coordenação de Biodiversidade, Instituto Nacional de Pesquisas da Amazônia, Manaus 69083-000, Brazil
Terumi Hatanaka
Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos 13565-905, Brazil
Sebastian Scholz
An der Nachtweide 16, 60433 Frankfurt, Germany
Alexander Meurer
Alfred Nobel Strasse 1e, 55411 Bingen am Rhein, Germany
Marcelo de Bello Cioffi
Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos 13565-905, Brazil
Although crocodilians have attracted enormous attention in other research fields, from the cytogenetic point of view, this group remains understudied. Here, we analyzed the karyotypes of eight species formally described from the Alligatoridae family using differential staining, fluorescence in situ hybridization with rDNA and repetitive motifs as a probe, whole chromosome painting (WCP), and comparative genome hybridization. All Caimaninae species have a diploid chromosome number (2n) 42 and karyotypes dominated by acrocentric chromosomes, in contrast to both species of Alligatorinae, which have 2n = 32 and karyotypes that are predominantly metacentric, suggesting fusion/fission rearrangements. Our WCP results supported this scenario by revealing the homeology of the largest metacentric pair present in both Alligator spp. with two smaller pairs of acrocentrics in Caimaninae species. The clusters of 18S rDNA were found on one chromosome pair in all species, except for Paleosuchus spp., which possessed three chromosome pairs bearing these sites. Similarly, comparative genomic hybridization demonstrated an advanced stage of sequence divergence among the caiman genomes, with Paleosuchus standing out as the most divergent. Thus, although Alligatoridae exhibited rather low species diversity and some level of karyotype stasis, their genomic content indicates that they are not as conserved as previously thought. These new data deepen the discussion of cytotaxonomy in this family.
