Elthusa epinepheli sp. nov. (Crustacea, Isopoda, Cymothoidae) a branchial parasite of the grouper Epinephelus howlandi (Serranidae, Epinephelinae) from off New Caledonia

The cymothoid isopod Elthusa epinepheli sp. nov., a branchial parasite of the blacksaddle grouper Epinephelus howlandi (Serranidae, Epinephelinae) from the coral reef of New Caledonia (Southwestern Pacific), is described and figured.Within the genus, E. epinepheli shows some similarity with E. raynaudii and E. myripristae. The ovigerous female of E. epinepheli can be distinguished from E. raynaudii by a less ovate body; cephalon deeply immersed in pereonite 1; eyes almost concealed by the amphicephalic processes; pereonites 3–7 distinctly decreasing in size (width and length); pleonites 1–5 distinctly increasing in width; and pleotelson larger. E. epinepheli can be distinguished from E. myripristae by the anterior margin of the cephalon being rounded in dorsal view and all pleonites being visible. E. epinepheli is the first species of Elthusa reported from the host genus Epinephelus.