Reproduction in Crepidula philippiana (Gastropoda, Calyptraeidae) from Southern Chile

Crepidula philippiana differs from most congeneric species in having only one embryo per capsule which attains a great hatching size, a feature shared only with C. monoxyla from New Zealand. In C. philippiana , this single embryo results from the ingestion of numerous nurse eggs. The clutch size (fecundity per spawn) is accordingly reduced. A significantly smaller but more uniform hatching size is observed among the remaining species of Crepidula , and clutch size is greater. Why do Crepidula species adopt different embryo nourishing mechanisms to attain direct development? Hypotheses considering ecological aspects and reproductive strategies are discussed.