A detailed karyological investigation of three endemic Cobitis L. 1758 species (Teleostei, Cobitidae) in Anatolia, Türkiye.

Abstract

Introduction: Comparative cytogenetics is a vital approach for diagnosing chromosome abnormalities and identifying species-specific patterns. In this study, chromosomal analysis of three Anatolian endemic Cobitis species was performed.

Methods: Conventional cytogenetic techniques such as Giemsa staining, C-banding and Ag-NOR staining were applied, followed by measurements of chromosome arm lengths including analysis of the measured data.

Results: The diploid chromosome number, 2n = 50, was determined for all three species. The karyotype formulas were as follows: four pairs of metacentric, five pairs of submetacentric, and 16 pairs of subtelo-telocentric chromosomes in Cobitis bilseli; 11 pairs of metacentric, seven pairs of submetacentric, and seven pairs of subtelo-telocentric chromosomes in C. fahireae; and four pairs of metacentric, four pairs of submetacentric, and 17 pairs of subtelo-telocentric chromosomes in C. turcica. Dark C-bands were observed on the pericentromeres of nearly all chromosomes in C. bilseli and C turcica, whereas light C-bands appeared on the pericentromeres of some chromosomes in C. fahireae. Silver-stained metaphases revealed signals on the short arm of a submetacentric chromosome pair in C. fahireae (each homologous chromosome carries one signal), while in C. bilseli and C. turcica, Ag-NOR signals were detected on the long arm of a single metacentric chromosome (only one homologous chromosome carries the signal, and the signal-carrying chromosome is the largest chromosome in the karyotype).

Conclusion: This study provides new cytogenetic data consistent with the phylogenetic distances between the studied species, indicating pericentric inversions and/or translocations that govern the formation of Cobitis karyotypes.