Abstract
The branchial-attaching cymothoid genus, Elthusa Schioedte & Meinert, 1884 is a genus with a worldwide distribution of 36 species, including the three species described here. Elthusaraynaudii (Milne Edwards, 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 species were identified, Elthusaraynaudii and three species that proved to be undescribed. Elthusaxenasp. 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. Elthusaacutinasasp. n. is identified by the produced and narrowly rounded cephalon anterior margin, acute uropods that are shorter than half the length of the pleotelson, and pereonite 1 anterior margin with medial projection. Elthusarotundasp. 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.
Highlights
Elthusa Schioedte & Meinert, 1884 is a branchial cavity-inhabiting cymothoid genus that was described as a monotypic genus for Elthusa emarginata (Bleeker, 1857)
Species descriptions were made with the aid of the taxonomy software package DELTA (Descriptive Language for Taxonomy), following a general Cymothoidae character data set originally developed by Hadfield et al (2010) and recently updated for other genera (Hadfield et al 2013, 2016b)
Elthusa raynaudii can be distinguished by the cephalon having a narrowly truncate rostrum; pereonite 1 with anterior margin straight; pleonites subequal in shape and width; and broadly rounded uropod apices that extend to more than half the length of the pleotelson
Summary
Elthusa Schioedte & Meinert, 1884 is a branchial cavity-inhabiting cymothoid genus that was described as a monotypic genus for Elthusa emarginata (Bleeker, 1857). Most species of Elthusa were originally described and placed within the genus Livoneca before their revision and redescription by Bruce (1990). Elthusa raynaudii (Milne Edwards, 1840) is the only species of Elthusa that has been described from sub-Saharan Africa. The lack of species records is most likely due to the lack of studying cymothoid isopods from this region and is not a true representation of the biodiversity of this genus. This paper forms part of a detailed study on the cymothoids from sub-Saharan Africa and confirms this postulation with the identification of three new species from the region
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