Genetic and morphological variations in populations of Oncomelania spp in China.

ABSTRACT

Oncomelania snails are the intermediate hoste of Schistosoma japonicum in Asian countries. In order to understand the genetic and morphological variation of Oncomelania snails in mainland China, field snails from 31 localities were collected and investigated by means of allele enzyme electrophoresis and numerical taxonomical technics. Results demonstrated that out of 17 loci examined, seven polymorphic loci were presented. Genetic distance (Nei, 1978) among the populations varied from 0.03 to 0.27. The phenogenetic tree based on UPGMA cluster analysis showed that genetic diversity corresponded to geographic distribution along the Yangtze River, which provided supplementary genetic data about the evolution of Oncomelania spp. A morphological study showed that Mahalanobis' morphological distance ranged from 1.53 to 346.7. Both genetic and morphological data indicated that the diversity among populations of smooth shelled snails was higher than that among populations of ribbed shelled snails. A positive correlation (r = 0.80) between Mahalanobis' morphological distance and genetic distance supports the hypothesis that the different shell phenotypes represent different species or subspecies.