Study of Biomphalaria Tenagophila Tenagophila, B. t. Guaibensis and B. Occidentalis by Polymerase Chain Reaction Amplification and Restriction Enzyme Digestion of the Ribosomal RNA Intergenic Spacer Regions

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Abstract
Biomphalaria tenagophila tenagophila, B. tenagophila guaibensis and B. occidentalis are indistinguishable on the basis of shell morphology and the majority of organs of the genital system. Only B. t. tenagophila is susceptible to infection with Schistosoma mansoni. The identification of this species is important for epidemiological studies of schistosomiasis. Snails from different sites in Brazil, Argentine and Uruguay were studied using the Polymerase Chain Reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP) of the Ribosomal RNA Internal Transcribed Spacers (ITS) using seven enzymes. Profiles resulting from digestion with AluI showed some invariant species-specific products allowing correct identification of B. t. tenagophila, B. occidentalis and B. t. guaibensis. Profiles obtained with other enzymes did not permit species identification as extensive intraspecific polymorphism or invariant RFLP profiles were observed. Restriction profiles obtained with all enzymes were used to calculate the percentage of band sharing between all individual snails and these data were used for a cluster analysis. A closer relationship between B. occidentalis and B. t. guaibensis than B. t. tenagophila and the subspecies B. t. guaibensis was observed. Based on previous morphological data and these molecular data, we propose grouping B. t. tenagophila, B. occidentalis and B. t. guaibensis into a B. tenagophila complex.

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