Meeting Abstract
P3.180 Tuesday, Jan. 6 Chromosome evolution of the cichlid fishes from Lake Victoria YOSHIDA, K*; KUROIWA, A; TERAI, Y; MIZOIRI, S; AIBARA, M; KOBAYASHI, N; MATSUDA, Y; OKADA, N; Tokyo Inst. of Technology, Yokohama; Hokkaido Univ., Sapporo; Tokyo Inst. of Technology, Yokohama; Tokyo Inst. of Technology, Yokohama; Tokyo Inst. of Technology, Yokohama; Tokyo Inst. of Technology, Yokohama; Hokkaido Univ., Sapporo; Tokyo Inst. of Technology, Yokohama yoshida.k.ah@m.titech.ac.jp
Lake Victoria in East Africa harbors more than 500 endemic cichlid species that are morphologically and ecologically diverse. Geological evidence suggests that the speciation event of the cichlids occurred in burst less than 15,000 years ago. This event is reflected by very low diversity of cichlid genome sequences, reported by the molecular genetics studies. The cichlids are studied as model system of speciation. Although studies of chromosome evolution may provide insight into speciation of cichlids, the cytogenetics study of the Lake Victoria cichlids has not been performed yet. Therefore, the aim of this study was to analyze the diversity of karyotypes of Lake Victoria cichlids in order to elucidate the relation between the chromosome evolution and the speciation. The karyotype analysis indicates that the cichlids from lakes Victoria and Malawi basically possess 44 chromosomes. Surprisingly, a few additional chromosomes were found in Lake Victoria species. The number of additional chromosomes is different among individuals. The karyotype analysis of F1 showed that the additional chromosome inherited by non-mendelian inheritance. These features suggest that the additional chromosome was thought to be B chromosome that is non-functional chromosome. B chromosomes have not been reported in African cichlids. 60% of the Lake Victoria cichlids possess two B chromosomes, 24% possess one and 7% possess three. Strikingly, the morphology of B chromosomes was various. This result suggests that B chromosomes appeared in the origin of the Lake Victoria cichlids and evolved through the process of the rapid speciation.
