Contributions to Zoology, 81 (2) 95-101 (2012) The ecology of shell shape difference in chirally dimorphic snails

The Southeast-Asian tree snail subgenus Amphidromus s. str. (Gastropoda Pulmonata: Camaenidae) is unusual among all gas-tropods for its genetic antisymmetry: populations consist of stable mixtures of individuals with clockwise (dextral) and counter-clockwise (sinistral) coiling directions. Although previous studies in A. inversus suggest that this genetic dimorphism is maintained by sexual selection, it cannot be ruled out that environmental fac-tors also play a role. Adult shell shapes in A. inversus are known to show subtle differences between both coiling morphs, and it is known that in snails in general, shell shape is under environmen-tal selection, thus creating the possibility that micro-niche use of both coiling morphs differs. In this paper, we first confirm that hatchlings also differ in shell shape. We then proceed with field studies to compare dextral and sinistral juveniles and adults for (i