COST OF RESISTANCE, EXPRESSED AS A DELAYED MATURITY, DETECTED IN THE HOST-PARASITE SYSTEM BIOMPHALARIA-GLABRATA ECHINOSTOMA-CAPRONI

Theoretical models have shown that when susceptibility to a parasite i s genetically determined, polymorphism with regard to susceptibility c an only be maintained by costs associated with resistance. However, an apparent resistance, or nonsusceptibility, may result from a lack of adaptation of the parasite, which does not imply any costs for the hos t. In this study, we analysed whether susceptibility was genetically d etermined in the Biomphalaria glabrata/Echinostoma caproni system, and we investigated the existence of costs associated with nonsusceptibil ity. Results showed that nonsusceptibility of B. glabrata to E. capron i was genetically determined and could be strongly selected for throug h generations. Furthermore, analysis of age at maturity among offsprin g segregating for susceptibility revealed that nonsusceptible individu als reached maturity later than susceptible ones. The delay in maturit y is statistically significant and reflects a cost associated with res istance.