Extensive karyotype variability of African fish genus Nothobranchius (Cyprinodontiformes)

Abstract

Karyotypes of 65 species of the genus <i>Nothobranchius</i> Peters, 1868 were reviewed and of those 35 examined first time. The results of present study have shown that fishes of the genus <i>Nothobranchius</i> possessed highly diverse karyotypes. The diploid chromosome number (2n) ranged from 16 to 50. The most frequent 2n was 2n = 36 (in 35 species) while the second one 2n = 38 (in 13 species). Proportion of biarmed chromosomes varied from 0 to 95% between species. Diploid chromosome number variability apparently exists as a result of chromosomal fusions or fissions and extensive karyotypic formula alterations promoting by inversions. Multiple sex chromosomes of system X₁X₁X₂X₂/X₁X₂Y type were found only in karyotypes of 5 species. The extensive karyotype variability, unusual for teleosts, of genus <i>Nothobranchius</i> can be likely associated with the characteristics of its life cycle and inhabiting under unstable environment of East African savannah temporal pools.