Some Notes on the Morphology of an Aberrant Actinian (Hexacorallia, Actiniaria) Associated with the Glaucothoe of the Hermit Crab Paguropsis typica Henderson (Anomura, Paguridae)

The planktonic glaucothoe of the Indo-West Pacific hermit crab Paguropsis typica Henderson has an aberrant anthozoan polyp, identified as a nynanthean actinian, attached to the underside of its thorax. The morphology of the anemone is described. The scapus is dumb-bell shaped and exhibits a slit-like mouth opening oriented transverse to the animal's siphonoglyphal plane. The gonads are very well developed, whereas tentacle-like structures or retractor muscles of certain septa are reduced. In the adult stage, Paguropsis typica is associated with the zoanthidean Epizoanthus paguropsides . It is assumed that the actinian is lost at the ecdysis leading to the first "hermit stage" and that P. typica might possibly seize a free Epizoanthus colony and adapt it to its body.