Karyotype Macrostructure in Two Species of Cobitis from Türkiye: A First Report for Cobitis battalgilae and a Re-examination of Cobitis turcica (Cypriniformes: Cobitidae)

Türkiye has a remarkable geography with its rich inland water ichthyofauna, where many endemic species are found, the genus Cobitis stands out as an important biodiversity element. This genus includes a group of loaches distributed in Europe, Asia and parts of North Africa, usually living in freshwater environments. There are 22 endemic species of Cobitis in Türkiye, distributed in Central, Western and South-Eastern Anatolia. The chromosomal characteristics of C. battalgilae have not been studied, limiting the scope of biological and ecological studies. We employed Giemsa-, C-, and Ag-NOR staining to characterise the karyotype macrostructure of two species of Cobitis from Türkiye, reporting cytogenetic data for the first time in C. battalgilae and reassessing previously known features of C. turcica. The diploid chromosome number in C. battalgilae and C. turcica was 2n = 50 and similar karyotype structures (8 m + 16 sm + 14 st + 12 a; NF = 74) were observed. In both species, there was a secondary constriction on the short arm of autosomal pair 1. Heteromorphic sex chromosomes were not detected. Constitutive heterochromatin (C-bands) was located in the peri/centromeric regions and differed in intensity on some chromosomes. Active Ag-NORs were detected on both homologues and were associated with heterochromatin on the largest metacentric chromosome pair (no. 1) in both species The cytogenetic findings of these two species supported the close relatedness revealed by phylogenetic analysis based on molecular (mitochondrial genes) data.