Karyotypes of four fish species from the Nile and Omo-Turkana basins in Ethiopia

Abstract

Mitotic chromosome sets in four fish species representing four different orders (Polypteriformes, Osteoglossiformes, Cypriniformes and Characiformes) occurring in the White Nile, Blue Nile and Omo-Turkana basins in south-western and northern Ethiopia were studied with the air-dried method of Kligerman and Bloom (1977). The following chromosome (2n) and arm (NF) numbers were found in these fishes: 2n = 36, NF = 72 in the gray bichir Polypterus senegalus (Polypteridae), 2n = 40, NF = 42 in the stonebasher Pollimyrus cf. nigricans (Mormyridae), 2n = 50, NF = 66 in the Abyssinian loach Afronemacheilus abyssinicus (Balitoridae) and 2n = 54, NF = 78 in the big-scale tetra Brycinus macrolepidotus (Alestiidae). Comparisons with the previously published data (reviewed by Arai, 2011) show general similarity in the gross karyotype features at the level of conspecific populations and congeneric species for the gray bichir, at the level of phylogenetically close genera and families for the Abyssinian loach and big-scale tetra, while substantial karyological differences were revealed between the stonebasher and two other mormyrid genera (Gnathonemus and Marcusenius) studied by Uyeno (1973).