Description of Idiomysis diadema sp. nov. (Mysida, Mysidae, Anisomysini), associated with Diadema urchins in the Red Sea; with nomenclatorial notes on its genus

Abstract

The mysid Idiomysis diadema sp. nov. is described from small swarms hovering between the spines of the sea urchin Diadema setosum (Leske, 1778) at the reef flat of Dahab, Red Sea. The most striking characters within its genus are the subdivided antennal scale, endopod of uropods longer than exopod, and a pair of minute spines on the terminal margin of the telson. With this first description, a total of six Idiomysis species are now known, two of which are associated with cnidarians and only the new one with echinoids. An updated definition is given for the genus Idiomysis W. M. Tattersall, 1922, in order to match the current species inventory. To avoid previously incorrect and ambivalent gender attribution, I propose using the feminine gender for this genus throughout. Consequently, the spelling of two of its taxa, I. mozambica Deprez, Wooldridge & Mees, 2001, and I. robusta Connell, 2008, is changed.