A comparative study of the karyotypes of Tilapia rendalli, T. sparrmanii and Oreochromis mossambicus (Cichlidae)

Abstract

Optimal chromosome preparations were obtained from stimulated lymphocyte cultures with a new method based on a combination and modification of several techniques. Tilapia rendalli, T. sparrmanii and Oreochromis mossambicus have somatic chromosome numbers of 44, 42 and 44, respectively. Chromosome pairs L1 and L2 are easily identified in all the karyotypes and distinctive of the tilapias. Tilapia sparrmanii has one additional large metacentric chromosome pair(L3), which occurs concurrently with the reduction of two in the total chromosome number. The F chromosomes were divided into two groups, viz a submetacentric (sm) and a telocentric (t) group. T. rendalli has 8 sm chromosomes, while both T. sparrmanii and O. mossambicus have 6 chromosomes in the sm group. The rest of the F chromosomes were telocentric. The identification of the sex chromosomes in the karyotypes of tilapia has thus far not been possible using standard techniques.