Abstract
ABSTRACT The genus Corydoras comprises a diversity of species with different diploid numbers. We compared cytogenetic data among Corydoras species from different rivers of the Ponta Grossa Arch region in southern Brazil. Corydoras ehrhardti and C. aff. paleatus have a similar karyotype formula and the same diploid number (2n = 44). Corydoras lacrimostigmata has a higher diploid number, with 2n = 58 chromosomes. Fluorescence in situ hybridization using 5S and 18S ribosomal DNA probes suggests that these ribosomal DNA sequences are involved in chromosomal rearrangements in these Corydoras species. 5S rDNA is a chromosomal marker that is considered to be unique to the species analyzed in this study. Signals of interstitial telomeric sites are seen in a chromosome pair of C. lacrimostigmata, suggesting chromosomal rearrangements via fusions or translocations. This study revealed that C. ehrhardti and C. aff. paleatus have exclusive chromosomal markers associated with chromosome differentiation, which we speculate to prevent genetic introgression.
Highlights
Corydoras Lacépède, 1803 (Callichthyidae: Corydoradinae), is a species-rich genus that comprises 216 species (Eschmeyer, Fong, 2016)
We focus on three southern Brazilian Corydoras species: C. ehrhardti Steindachner, 1910, C. lacrimostigmata Tencatt, Britto & Pavanelli, 2014, and C. aff. paleatus (Jenyns, 1842)
Specimens were deposited in the Coleção Ictiológica do Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (Nupélia) of the Universidade Estadual de Maringá, Maringá, Brazil
Summary
Corydoras Lacépède, 1803 (Callichthyidae: Corydoradinae), is a species-rich genus that comprises 216 species (Eschmeyer, Fong, 2016). The 18S rDNA probe was labeled with biotin-11-dUTP (Roche Applied Science), Conventional cytogenetic analysis showed that the populations/species of C. ehrhardti (Tibagi River basin), C. aff. Paleatus (Ribeira River basin) have a diploid number (2n) of 44 chromosomes, a karyotype formula of 18m + 26sm, and a fundamental number of chromosome arms (FN) of 88
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