Chromosomal polymorphism in the goby Neogobius eurycephalus (Perciformes: Gobiidae)

Abstract.

The karyotype of a goby, Neogobius eurycephalus, was studied using C-banding, silver (Ag^–) staining and fluorescence CMA₃-staining. Interindividually variable diploid number (2n=30–32) due to Robertsonian variation has been found, resulting in three karyomorphs. Analysis of the meiotic chromosomes suggested a balanced segregation of heterozygotes. Nucleolar organiser regions (NORs) were detected in the pericentromeric region of one pair of the metacentric chromosomes, and sequential stainings documented that they are C-banding and CMA₃-positive, suggesting the presence of GC-rich heterochromatin. Heterochromatin blocks were located mostly in centromeric regions, those of GC-rich type in the bi-armed and uniarmed chromosomes. The present observation again evidences that Robertsonian fusion among gobiid fishes is the main chromosomal rearrangement in the differentiation of their karyotypes. The present study also documents the importance of chromosomal studies in the systematics studies of gobiids.