Predation by Gecarcoidea lalandii (Crustacea, Gecarcinidae) on dextral and sinistral Amphidromus inversus (Gastropoda, Pulmonata, Camaenidae)

The tropical tree snails of the subgenus Amphidromus s.str. receive much attention from researchers because populations consist of roughly equal proportions of dextral and sinistral individuals. Studies indicate that this stable genetic antisymmetry is maintained because of disassortative mating. Deviations of the theoretically expected 50:50 proportion have, however, been frequently reported. An explanation for this deviation could be modulation by chirally biased predation. On the island of Kapas, Malaysia, seventeen individuals of Gecarcoidea lalandii, a nocturnal terrestrial crab, were caught and housed with live Amphidromus inversus. A low level of predation by the crab on the snails was found. However, there is no reason to assume that predation by G. lalandii is chirally biased.