A New Polyclad Turbellarian Associating with a H ermit Crab in the Hawaiian Islands

AT THE REQUEST of Dr. Ernst S. Reese of the Universi ty of Hawaii the wri ter has studied seven specimens of a polyclad turbellarian found in the shells of Trocbus sand taicbensis occupied by the hermit crab Calcines latens in Kaneohe Bay, Oahu, Hawaiian Islands. Accord ing to Dr. Reese ( in litt. ) the worm wraps itself around the abdomen of the crab and usually occurs deep in the spira l cavity of the molluscan shell. W hen dislodged from its shelter and placed in a dish of water together with the crab in its shell, the worm tries to re-enter the shell, but only one case was actually seen of the worm entering. The frequency with which this association occurs is about one per 25-30 crabs, but a particularly high incidence of four worms to 60 crabs was found on March 7, 1967, in the same location in Kaneohe Bay. Apparen tly the polyclad has not been found in the shells of other hermit crabs, Calcines laeoimanus and Clibanarins zebra, associating with Calcines latens, although the three species use T rocbus snnd ioicbensis shells, and the only ecological difference between them is that Calcines latens extends further down into the sub-tidal than does either of the other two species. The present specimens und oubtedly belong to the genus Em prostbopbarvnx and appear to represent a new species. They were first noticed by Dr. Reese's research assistant, Mrs. Anne Phillips Rasa, and the writer has much pleasure in naming the species after her. The writer would like to thank Dr. Reese for giving him the opportunity of examining the worms, and for providing information on their behaviour. Th e type specimens are deposited in the collections of the British M useum (Natural H istory) .