Identification, characterization, and larval biology of a rhizocephalan barnacle, Sacculina yatsui Boschma, 1936, from northwestern Japan (Cirripedia: Sacculinidae)

We investigated the biology and host-parasite interaction in the rhizocephalan cirriped Sacculina yatsui (Boschma, 1936) (Sacculinidae) infecting the Asian shore crab Hemigrapsus sanguineus (De Haan, 1835) (Varunidae) at the Oga Peninsula, Akita, Japan. We identified the parasite based on molecular and morphological information. We describe the establishment of a system for long-term laboratory maintenance of the host-parasite interaction, and provide information on the larval biology of the species, including duration of larval stages, brood release intervals, sizes of male and female cypris larvae (cyprids), and changes in the ratio of cyprids among broods. Sacculina yatsui mainly settles on the thin and flexible arthrodial membranes of the chelipeds, maxillipeds, and pereiopods of the host. Preliminary analysis of transcriptome in the nauplii of the parasite indicated that four out of the top ten most highly expressed transcripts are related to the formation of the chitinous cuticle. Our results will provide a useful basis for subsequent transcriptomic studies to address the molecular mechanisms underlying larval biology and the biological interactions between rhizocephalans and their hosts.