Meeting Abstract

S10-1.4  Saturday, Jan. 7  Metamorphosis in balanomorphan, pedunculated and parasitic barnacles: A video based analysis HOEG, JT*; CHAN, BKK; GLENNER, H; MARUZZO, D; OKANO, K; University of Copenhagen; Academia Sinica; Bergen University; University of Padova; Akita Prefectural University

All barnacles pass a profound metamorphosis between the larval phase and the attached juvenile. We use video microscopy to study metamorphosis in both suspension feeding thoracicans and in parasitic rhizocephalans. The morphology of the cirripede cyprid is incompatible with that of the ensuing juvenile form, whether suspension feeding or parasitic. Therefore, the reorganization involved in metamorphosis can only commence after permanent attachment, but must then proceed rapidly because the attached cyprid has limited energy resources and faces external dangers such as desiccation, predation, or removal by the host animal. In all cirripedes the metamorphic moult is initiated by a slight separation of the integument from the cyprid cuticle, and antennular muscles participate in the ensuing process. In balanomorphans a rotation of the body assures the correct orientation of the cirri, and pulsating movements of the prospective juvenile results in elimination of the cyprid carapace. The compound eyes are shed just before this event. Metamorphosis lasts from a few hours (Balanomorpha, Rhizocephala) to several days (pedunculates). The free balanomorphan juvenile is rather shapeless, with very thin cuticle and continues its pulsating movements, but it quickly assumes the volcano shape of a barnacle with incipient shell plates and beating cirri. Pedunculated forms have a more gradual metamorphosis. In rhizocephalans, female cyprids moult into a kentrogon, which after two days use a stylet to penetrate into the host and enter as a simplified vermigon stage, the injection lasting seconds only. Elimination of the cyprid carapace is essential in thoracicans but not in all rhizocephalans.