ABSTRACT
In gonochores, female and male sexes are expressed and functional in separate individuals. Jame and Auld estimated from Heller ‘s data that hermaphroditism has originated independently at least 40 times from the ancestral gonochoric gastropods. Yet, it must be noted that among the earliest diploplastic Porifera, most of them are hermaphrodites but function as behavioral gonochores. To reduce the cost of semen production, gonochorics have adopted the following strategies: reduction in male ratio at population level and reduction in somatic size of males and/or production of semelparous males. Labile sex differentiation has been demonstrated in the echiuran Bonellia and cirripedes. In cirripedes, the cyprid larva settling on the mantle rim of conspecific hermaphrodite metamorphoses into a dwarf male but that on a substratum becomes a hermaphrodite. Androdioecy is constituted by the presence of hermaphrodites and males. It is common among notostrocan (12 species) and spinicaudatan (40 species) crustaceans.
