Chromosomal analysis of the freshwater fish Mormyrus rume (Mormyridae) from Asejire Reservoir, Oyo State, Nigeria

Abstract

There is sparse cytogenetic information on 7 genera out of 22 genera and about 206 out of 225 species of the family: Mormyridae. To enhance the understanding of chromosome patterns in the family, cytogenetic data on these genera and species are essential. In this study, the first of such data on Mormyrus rume, including the standard karyotype, and C- and Ag-NOR banding, were determined and presented. This was to investigate their chromosomal patterns and provide additional information for comparative analyses. The results showed that, M. rume exhibited 2n = 50 (24m+10sm+16a), NF = 84. C-bands were observed in the centromeric portion of all the chromosomes. Telomeric C-bands were noticed in a pair of sub-metacentric chromosomes while nucleolar organiser regions were located in the interstitial position of a pair of metacentric chromosomes. Pericentric inversion and Robertsonian events appeared to be the major evolutionary mechanisms responsible for chromosome evolution in the species.