Graphical abstract

The genus Cymothoa Fabricius, 1793 is revised for southwestern Indian Ocean waters. Cymothoa borbonica Schioedte & Meinert, 1884 and C. eremita Brünnich, 1783 are redescribed. Cymothoa rotundifrons Haller, 1880, from Mauritius lacks type material and the host is unknown, therefore it is here relegated to nomen dubium. Cymothoa sodwana sp. nov., from Trachinotus botla (Carangidae), collected from the Kwazulu-Natal coast of South Africa, is described and is distinguished by the large, ovoid, hunched body with rugose dorsal surfaces; the anterolateral angles of pereonite 1 are narrow and rounded reaching half the length of the cephalon; the ischium of pereopod 7 has a large protrusion and pereonite 7 which laterally overlaps the pleon margins, extending posteriorly to the pleotelson.

The global translocation and introduction of freshwater fish into non-native regions has created the perfect opportunity for the co-introduction of their parasites. In a recent review on non-native freshwater fish introductions in South Africa, 55 fishes were reported as introduced into novel environments in South Africa, with 27 alien and 28 extralimital. However, the parasites potentially co-introduced by these non-native fishes have received much less attention from researchers than the hosts themselves. Thus far, the only attempts at summarising our knowledge on the diversity of introduced freshwater fish parasites in this region dates back to the 1980s when only four parasite species were considered to be alien, with a further eight species as doubtful. Over the last thirty years, more records have been added and this paper aims to provide an up-to-date review of our knowledge on the diversity, distribution, status (co-invasive or co-introduced) and the direction for future studies on introduced freshwater fish parasites in South Africa. Here we consider seven species (four ciliates, and one cestode, copepod and branchiuran respectively) as confirmed co-invaders, and 16 species (one flagelate, four ciliates, one cestode and ten monogeneans) as co-introduced. In addition, six species (three ciliates, two monogeneans and one copepod) previously recorded as invasive are deemed to be of uncertain status, and one ciliate is removed from the list of known invasive parasites from this region. It is further proposed that future research should focus on extralimital co-introductions, especially in the Eastern and Western Cape regions of South Africa where more than half of the fishes present are introduced species. It is also recommended that all new records of introduced parasites and new distribution records of known invasive parasites should include the deposition of voucher specimens in museums and, as far as possible, include molecular confirmation of its identification.

The parasitic isopod Cinusa tetrodontis Schioedte and Meinert, 1884, is the only species in Cinusa and has one known host, the evil-eye puffer fish, Amblyrhynchotes honckenii. The original Latin description contained many generic or family traits and thus the genus and species are redescribed. A complete revision of the genus was carried out, detailed illustrations of C. tetrodontis are provided and a lectotype designated and deposited in the Zoological Museum, University of Copenhagen.