The cypris larvae of Sacculina carcini Thompson (Crustacea: Cirripedia: Rhizocephala)

Abstract

Populations of nauplii of the parasitic barnacle, Sacculina carcini Thompson were cultured to the cypris stage at various times throughout the year. In all 28 populations were studied. The carapace length of 310 cyprids from each population was measured and the data showed that only large “male” cyprids occurred during the autumn and winter. The smaller “females” appeared in the populations during the summer, making up all of a population or mixed in varying proportions with “males”. Relaxed cyprids, both “males” and “females”, were studied with the light microscope and the scanning electron microscope and differences in antennular morphology observed. The absence of the large posterior sac in the “female” is a clear distinguishing feature. The antennular morphology of S. carcini is compared with that found for the cyprid of the thoracican barnacle, Balanus balanoides (L.). Settlement experiments using “female” cyprids of Sacculina carcini showed the wide range of sites selected on the crab and also the long post-settlement period needed for the inoculation stage (kentrogon) to develop.