OBSERVATIONS ON THE LARVAL DEVELOPMENT OF SACCULINA-CARCINI (CRUSTACEA, CIRRIPEDIA, RHIZOCEPHALA)

The larval development of the parasitic barnacle, Sacculina carcini, has been closely followed. Size and volume measurements have been made for the four naupliar stages and cyprids of both male and female broods. Volume increases between naupliar stages and cyprids of both male and female broods. Volume increses between naupliar stages were minimal (.times. 1.03-1.09) and in line with other barnacle species with lecithotrophic larvae. However, the large volume reduction between stage IV and cyprid for S. carcini, which is more acute for the female larvae, is a unique characteristic. The reduced setation formulae of the larval appendages of S. carcini and another rhizocephalan are compared to those of larvae, both lecithotrophic and planktotrophic, of a range of barnacles. Sex ratios and carapace length data for 184 S. carcini cypris populations are presented which reinforce the seasonal changes in sex ratios.