Assessment of genetic heterogeneity within laboratory-maintained Schistosoma mansoni-resistant stocks of Biomphalaria glabrata snails by RAPD-PCR

Abstract

Random amplified polymorphic DNA (RAPD)-PCR analysis was used to assess the extent of genetic diversity within two laboratory-maintained Schistosoma mansoni-resistant stocks of Biomphalaria glabrata (10-R2 and BS-90). Both stocks routinely serve as parents in crosses with susceptible snails for studying the genetics of parasite resistance in the snail host. Genomic DNA was isolated from individual adult 10-R2 and BS-90 snails. From RAPD-PCR conducted with 16 anonymous primers, no polymorphisms were detected within the BS-90 stock, whereas 13 primers revealed considerable intrastrain variations showing different sized bands among the 10-R2 snails. The polymorphisms in the 10-R2 stock allowed us to identify three distinct groups (Types 1, 2 and 3) within these snails. Random screening of individual 10-R2 snails revealed that, of the three distinct types, Types 1 and 2 snails were found at similar frequencies (approximately 45%), whereas 10% fell into the third group (Type 3). The identification of genetic variants within the 10-R2 stock demonstrates the need for careful assessment of the existence of diverse forms in this stock prior to conducting genetic crosses with these snails.