title: Comparative karyology of the freshwater snails Bulinus tropicus and B. natalensis.
abstract: Species of the subgenus Bulinus s.s. occur in a polyploid series which is of interest because of the rarity of polyploidy in animal species and because there appears to be a relation between ploidy level and ability to transmit Schistosoma haematobium, a parasite of major public health importance. We describe a technique for the preparation of standard karyotypes using cell suspensions from colchicine-treated embryos. The results for two diploid species, B. tropicus (Krauss) and B. natalensis (Küster), are presented. Both karyotypes consist of 15 metacentric and 3 submetacentric chromosomes. However, differences in centromere position are found in four pairs of chromosomes, and in the appearance of a secondary constriction. Because B. natalensis may represent a relict taxon involved in the origin of the polyploids, the results of significance for future work on the phylogeny of this group.
mesh_terms: D000818:Animals; D002033:Bulinus / Q000235:genetics*; D002871:Chromosome Banding; D002875:Chromosomes / Q000648:ultrastructure*; D004199:Disease Vectors; D007621:Karyotyping; D011003:Ploidies; D012552:Schistosomiasis; D013045:Species Specificity