Geographical Variation of Shell Morphology in Cypraea Annulus(Gastropoda: Cypraeidae)

摘要

Macro- and microgeographic variation of shell morphology in Cypraea annulus was studied. Surveys of phenotypic variation in 19 populations from the Indian and West Pacific Oceans revealed a significant positive relationship between average seawater temperature and callus thickness. In contrast, juvenile shell size after maturation had no significant relationship with seawater temperature. Research on within-population variation in Okinawa Island indicated that shell morphology is correlated with some ecological factors such as temperature and algal abundance. Both juvenile shell size and callus thickness decreased with increasing density of individuals. These microgeographical patterns suggest that ecophenotypic variation, rather than genetic differentiation, causes the latitudinal clines in shell morphology that have been reported in several cypraeid species.