Chromosomes of Snails in Bulinus Truncatus / Tropicus Complex: Study of Chromosome Number in Snail Species of Bulinus Truncatus / Tropicus Complex from Various Localities in Ethiopia

Freshwater snails of the Bulinus truncatus/tropicus complex occur in Ethiopia at various ploidy levels (diploid, tetraploid, hexaploid and octoploid) which are otherwise rare in other animal phyla. The present study provides data on the occurrence and distribution of the various ploidy levels of B. truncatus/tropicus complex from 14 localities in Ethiopia based on meiotic bivalent chromosome counts. Emphasis was put on the use of shell morphology and chromosome number in species identification within B. truncatus/tropicus group. Chromosome preparation was made from gonadal tissue (ovotestis). The result showed that five of the 14 sites studied contained diploid populations. These were Wondogenet, Lake Awasa, Lake Ziway, Wonji irrigation system and Lake Hora, which are mostly in low altitudes. Hexaploid populations were obtained from three sites: Legadadi, Aleltu and Chacha while octoploid populations were found in four sites: Sululta, Debreberhan, Bati and Gefersa streams. Tetraploid populations were observed from three sites: Lake Hora, Senkale and Gerbi. In Lake Hora, both diploid and tetraploid populations were occurring together in the same micro-habitat.