Review of the fish parasitic genus Elthusa Schioedte & Meinert, 1884 (Crustacea, Isopoda, Cymothoidae) from South Africa, including the description of three new species

Abstract

The branchial-attaching cymothoid genus, Elthusa Schioedte & Meinert, 1884 is a genus with a world-wide distribution of 36 species, including the three species described here. Elthusa raynaudii (Milne Ed-wards, 1840) is the only species that has been described from southern Africa. All South African material held at the National Museum of Natural History, Paris, France (MNHN) and the Iziko South African Museum, Cape Town (SAMC) identified as, or appearing to belong to, Elthusa was examined. Four spe-cies were identified, Elthusa raynaudii and three species that proved to be undescribed. Elthusa xena sp. n.can be distinguished by an evenly rounded pereonite 1 anterior margin, a roughly rectangular pleotelson, and narrowly rounded uropod apices that extend to more than half the length of the pleotelson. Elthusa acutinasasp. n. is identified by the produced and narrowly rounded cephalon anterior margin, acute uro-pods that are shorter than half the length of the pleotelson, and pereonite 1 anterior margin with medial projection. Elthusa rotundasp. n. is characterised by the round body shape, broadly rounded uropod apices, and protrusions on the proximal and lateral margins of the merus and carpus of pereopod 7. A key to the South African Elthusa species is provided, together with a table summarising the hosts and localities of the 33 previously known species of Elthusa