Parasite diversity of African longfin eel Anguilla mossambica Peters with comments on host response to the monogenean Pseudodactylogyrus anguillae (Yin and Sproston)

Parasite diversity and community structure of translocated Clarias gariepinus (Burchell) in South Africa: Testing co-introduction, parasite spillback and enemy release hypotheses

Clarias gariepinus (Burchell) is one of several freshwater fish species that have been translocated beyond its natural geographic range in South Africa. The present study investigated the parasitic communities of two translocated populations (one in the Riviersonderend River, Western Cape and the other from the Great Fish River, Eastern Cape) as well as its native source population from Gariep Dam, Free State. A total of nine, seven, and eight parasitic taxa were found to parasitise various organs of C. gariepinus from the three populations, respectively. The diversity and abundances of parasitic species in the two translocated populations were similar, but distinct community assemblages were observed. Parasite community composition from the Great Fish River was similar to that of the source population from Gariep Dam, whereas the parasitic community from C. gariepinus in the Riviersonderend River was distinct from that of Gariep Dam. This, together with the introduction history into the Western Cape, suggests that translocated C. gariepinus is sourced from various systems across South Africa, or that suitable intermediate hosts are present in the recipient ecosystems to sustain host-specific co-introduced parasitic taxa of C. gariepinus. In total, the resilience of 11 specialist parasite species of C. gariepinus is demonstrated in their persistence upon co-introduction into the two novel environments with their host, and support for the enemy release hypothesis is confirmed in the loss of known parasite taxa in translocated populations. The presence of the co-invasive fish lice Argulus japonicus Thiele, 1900 is reported from C. gariepinus in Gariep Dam and the Asian tapeworm Schyzocotyle acheilognathi (Yamaguti, 1934) was found from translocated C. gariepinus in the Riviersonderend River, Western Cape and lastly, a suspected case of parasite spillback from an unknown native host is reported.

Pseudodactylogyrus anguillae (Yin & Sproston, 1948) from the giant mottled eel Anguilla marmorata Quoy & Gaimard, 1824, in the Phongolo River, South Africa: an invader on the African continent

The global invasive anguillid gill parasite Pseudodactylogyrus anguillae (Yin and Sproston, 1948) has only recently been documented from eels in South Africa. As there is no known eel trade in South Africa, the source of introduction of this parasite has been debated, and its status as an alien parasite was rendered uncertain. We report on the first infection of Pseudodactylogyrus anguillae from the giant mottled eel Anguilla marmorata from the Phongolo River (South Africa) using classic morphological and molecular methodologies and clarify the introduction status category of this parasite as alien and invasive.

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

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.