Moleculer cytogenetic properties of spirlin alburnoides kosswigi (cypriniformes, leuciscidae)

Recent advances in ichthyological studies of Türkiye's freshwater systems have led to the description of a new species, Alburnoides kosswigi, in 2017. A. kosswigi is an endemic species distributed in the Sakarya River drainage in central Türkiye. Based on this background, the present study aimed to analyze the cytogenetic characteristics of A. kosswigi specimens collected from the Ilgın Lake Basin (Konya Province) using both conventional and molecular approaches. Conventional Giemsa staining revealed a diploid chromosome number of 2n = 50 in both sexes, and the karyotype formula (12M + 24Sm + 8St + 6A) was found to be consistent with the conservative karyotype pattern commonly observed in the subfamily Leuciscinae. Additionally, four Ag-NOR signals were detected at the terminal regions of the short arms (p) of two subtelocentric chromosome pairs. C-banding analysis has shown that constitutive heterochromatin blocks are present in the centromeric and pericentromeric regions of all chromosomes, and telomeric C-band is also present on the acrocentric chromosome 23. Fluorescence in situ hybridization (FISH) analyses revealed distinctive cytogenetic features of A. kosswigi concerning the chromosomal distribution of 5S and 18S ribosomal RNA genes (rDNA), U1 and U2 snDNA, and telomeric (TTAGGG)n repeats. Twelve 5S rDNA loci were identified on six chromosome pairs, whereas 18S rDNA signals were localized on two pairs (four loci in total), and another single subtelocentric pair carried a single co-localized U1/U2 snDNA site. The findings highlight the necessity for further comprehensive molecular cytogenetic studies across the genus Alburnoides to obtain more reliable comparative data and to better understand chromosomal evolution and interspecific relationships within this group.