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