Periclimenes attenuatus sp. nov. (Crustacea, Decapoda, Natantia, Pontoniinae), a New Commensal' Shrimp from the Duke of York Islands

Periclimenes attenuatus, a new species of pontoniid found in association with an unidentified crinoid from the Duke of York Islands, New Ireland, Bismarck Archipelago, is described and its morphology illustrated. The distinctive features of the shrimp and its relationship to other species of the genus is discussed. The information available concerning pontoniid-crinoid associations is reviewed and tabulated. THE SPECIES of the genus Periclimenes Costa, 1844, are found in association with a wide variety of invertebrate hosts representing several phyla. Amongst these species many are found as commensals of the Echinodermata, where they are particularly associated with the Crinoidea, Echinoidea, and Asteroidea, although a few examples have also been reported in association with ophiuroids (Gorgonocephalidae) and holothurians. The first species of Periclimenes reported in association with a crinoid was Periclimenes amboinensis. This species was described by De Man in 1888, on the basis of a single specimen obtained from Ambon, Indonesia. The host was not identified and the species has not been recorded since. Another species was described by Zehntner in 1894 and the host was, on this occasion, identified as an Actinometra. Subsequently, in 1915, Borradaile described a number of new species of several genera and the hosts of some of these were identified to specific level. Kemp, in 1922, listed the species then known to be associated with crinoids in the Indo-WestPacific region and a more detailed list was provided in 1952 by Holthuis who tabulated the available information for all pontoniid shrimps. A similar list was provided for crinoid associates by Balss (1956). Bruce (1965) provided a list of the echinoderm associates of the Indo-West-Pacific species of Periclimenes, In1 Manuscript received January 4, 1971. 2 East African Marine Fisheries Research Organization, P. O. Box 81651, Mombasa, Kenya. eluding the crinoids. Information upon the crinoid hosts is still deficient and the range of host variation for most species is poorly known. It is also possible that some of the less-wellknown species of pontoniid shrimps will be found to have· crinoid associations. Through the kindness of Dr. R. U. Gooding, I have been able to examine some specimens of Periclimenes that he collected from crinoids in the Bismarck Archipelago, which upon examination proved to belong to another undescribed species. A report upon these specimens is presented in this work. I am grateful to Miss A. M. Clark for the identification of the crinoid hosts referred to in this paper. Periclimenes attenuatus sp. nov.