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.