Larval Development in the Rhizocephalan Barnacle Sacculina pilosella

We studied, under laboratory conditions, the larval development of a rhizocephalan barnacle Sacculina pilosellaVan Kampen et Boschma, 1925, which parasitizes the kelp crab Pugettia quadridens(de Haan) in Vostok Bay, Sea of Japan. It is shown that at 22–23°C, the whole cycle of larval development takes about 3 days. The larvae of S. pilosellaare lecithotrophic; their development, like in other rhizocephalans, comprises five naupliar instars. Like the larvae of all sacculinids, the nauplii of S. pilosellahave no flotation collar. In their structure, the larvae of S. pilosellaare similar to the nauplii of the typical sacculina, S. carcini(elongated body outline, long furcal branches, and weakly pronounced segmentation of the abdomen). On the other hand, the characteristic outgrowth inbetween the furcal branches that is characteristic of stages IV and V in S. carciniand S. polygeneais absent in the larvae of S. pilosella.The first seta on the antennula of S. pilosellacompletely disappears only at stage IV; however, at stage III, it is already significantly reduced. No morphological differences have been revealed between male and female larvae of S. pilosellaexcept certain size differences.