Alien freshwater fish parasites from South Africa: Diversity, distribution, status and the way forward

Abstract

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.

Biotic Interactions as Mediators of Biological Invasions: Insights from South Africa

“…The introduction of 27 alien fishes to South Africa has provided opportunities for at least 23 parasitic co-introductions of ten monogeneans, eight ciliates, two cestodes, a copepod, a flagellate, and a branchiuran (Smit et al 2017). Most (16) of these parasites are not known to have infected native fishes (Smit et al 2017). For example, five ancyrocephalid monogeneans are found only on the alien Largemouth Bass, Micropterus salmoides.…”

“…Despite the almost ubiquitous presence of bass in South African rivers (Ellender et al 2014), these parasites have not been observed to infect native fishes to date (Truter et al 2017). The other seven co-introduced parasites, however, have formed new associations with native hosts, probably because of broader levels of generalism in their symbiotic requirements (Smit et al 2017). While significant impacts on the health status of novel hosts have been documented (see Weyl et al 2020, Sect.…”

Morphological and molecular characterization of myxobolids (Cnidaria, Myxozoa) infecting cypriniforms (Actinopterygii, Teleostei) endemic to the Iberian Peninsula

“…The common carp Cyprinus carpio, for instance, is largely recognized as being responsible for numerous co-introductions and co-invasions of different parasitic groups worldwide, including myxozoans (e.g. [50,60,68,71,76]). Reported cases of co-introduction with C. carpio include the myxobolid species Thelohanellus hovorkai Akhmerov, 1960 and T. nikolskii Akhmerov, 1955, both originally from the Amur basin and later introduced to Hungary [48,50].…”

A neglected fish stressor: mechanical disturbance during transportation impacts susceptibility to disease in a globally important ornamental fish

“…Due to mixing of species from different geographic regions, disease dynamics in wholesalers, retailers and hobbyist aquaria may result in parasite host switching and increased virulence (Kelly et al 2009). Accidental or intentional introduction of exotic species into local fish populations can cause transmission of highly virulent parasites to which native fish species may be especially susceptibile 90 (Smit et al 2017). 91…”