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 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.

A new genus and species of fish parasitic cymothoid (Crustacea, Isopoda) from the Indian Ocean coast of South Africa, with a key to the externally attaching genera of Cymothoidae

“…Unidentified material from Sodwana Bay, South Africa, was loaned from the Iziko South African Museum ( SAMC ). Methods follow Hadfield et al (2010) and van der Wal et al (2019). Species descriptions were prepared using DELTA (Descriptive Language for Taxonomy), following a general Cymothoidae character data set originally developed by Hadfield et al (2013) and recently updated (Hadfield et al 2016).…”

“…The South African cymothoid fauna had remained little studied, with only 12 species in seven genera reported (Kensley 1978) until the recent revisions of Hadfield et al (2010, 2013, 2014a, 2014b, 2015; Hadfield and Smit 2017), Van der Wal et al (2017, 2019), and Welicky and Smit (2019), now with 21 species in eight genera. The major taxa remaining to be revised are the externally attaching genera Nerocila and Renocila , both of which have numerous unreported species in the Western Indian Ocean region (pers.…”

Exceptionally preserved cryptoniscium larvae - morphological details of rare isopod crustaceans from French Cretaceous Vendean amber

“…Yet, based on their ecological function (dispersal) they may be interpreted as functional larvae (if dispersal is considered a larval feature; see Haug, in press). In Cymothoidae subsequently gradual morphological changes in favour of a close parasite-host interaction can happen, which can, for example, lead to the loss of the bilateral symmetry in late stages of the individual development (e.g., van der Wal et al, 2019).…”

Triple barcoding for a hyperparasite, its parasitic host, and the host itself: a study of Cyclocotyla bellones (Monogenea) on Ceratothoa parallela (Isopoda) on Boops boops (Teleostei)

“…Overall, the Cymothoidae are taxonomically challenging as descriptions of many species were originally based only on the morphology of few or sometimes single specimens, thus providing no information on polymorphism [ 76 ]. In addition, many misidentifications and incorrect data on species were generated when not considering the morphological variability ascribed to the parasitic lifestyle of cymothoids, polymorphism and sister species, as well as the variations in attachment site and the morphological adaptations [ 29 , 72 , 76 ]. In recent years, numerous genera and species described early were revised, eliminating some of the uncertainties and confusion [ 30 , 72 , 76 ].…”