Ciliophora

Smit, Nico J., Malherbe, Wynand & Hadfield, Kerry A., 2017, Alien freshwater fish parasites from South Africa: Diversity, distribution, status and the way forward, International Journal for Parasitology: Parasites and Wildlife 6 (3), pp. 386-401 : 395

3.2. Phylum Ciliophora

3.2.1. Trichodina acuta

The mobilid peritrich, T. acuta , is a known invasive parasite and has, since its original description, been reported from at least seven different non-native regions ( Basson and Van As, 1993). In South Africa, Basson et al. (1983) reported T. acuta from four cichlids and two cyprinid species collected at more than six different localities in the northern provinces of South Africa. These hosts included T. acuta 's type host, C. carpio , and thus further strengthened their conclusion that this parasite is a co-introduced species that spilled over to South African native fishes. However, in their remarks on the species, Basson et al. (1983) commented on the distinct variability in size and denticle dimensions between the South African population and those reported from Israel and the Philippines. Van As et al. (1984) also reported what they identified as T. acuta from a Fisheries Research Station where it was implicated in the mortalities of two different fish species. Bruton and Merron (1985) and De Moor and Bruton (1988) further included this species in their respective lists of confirmed invasive aquatic invertebrates. In their review on the taxonomic status of fish ectoparasitic trichodinids, Van As and Basson (1989), with new information available to them, re-evaluated their original records of T. acuta from South Africa. By using additional characteristics which enabled them to provide a better understanding of differences in denticle shape, Van As and Basson (1989) described what was previously identified as a South African population of T. acuta , as all belonging to a new species, Trichodina compacta Van As and Basson, 1989 , thereby removing T. acuta from the list of invasive parasites from South Africa. However, a few years later, Basson and Van As (1993) accurately identified T. acuta in South Africa and this time on rainbow trout, Oncorhynchus mykiss (Walbaum, 1792) . This species was collected from a cage culture on a trout farm in the Free State province of South Africa (Table 1, Fig. 2D ) confirming its status as a co-introduced parasite in South Africa. Basson and Van As (1993) also provided a detailed discussion on possible routes of introduction into South Africa, especially since its native hosts are European and Asian cyprinids and not salmonids, and concluded that it must have been a recent introduction and future research should focus on the potential spillover to South African native hosts.

3.2.2. Trichodina mutabilis

The history of discovery of T. mutabilis from South Africa is similar to that of T. acuta (see above) and thus not repeated here in detail. In short, Basson et al. (1983) reported this species from various invasive and native hosts in South Africa and then later Van As and Basson (1989) redescribed those specimens thought to be T. mutabilis as two species new to science, Trichodina kazubskii Van As and Basson, 1989 parasitising native fishes and Trichodina uniforma Van As and Basson, 1989 from the introduced C. auratus (see section 3.2.4). More than ten years later, Mouton et al. (2001) reported T. mutabilis again from South Africa, describing this parasite from C. carassius during a health survey of ornamental fishes imported to South Africa (Table 1, Fig. 2D ). The fact that spillover of T. mutabilis to native non-cyprinid hosts in India ( Mitra and Bandyopadhyay, 2005), and its heavy infection on moribund C. carpio in an aquaculture facility in the USA ( Kritsky and Heckmann, 2002) has been reported, shows the potential threat of this co-introduced parasite to both native species and aquaculture in South Africa.

3.2.3. Trichodina reticulata

As one of the most prevalent ectoparasites of the goldfish, C. auratus , it is not surprising that T. reticulata has a similar global distribution to that of its popular ornamental fish host. Basson and Van As (1993) found this to be true when they recorded T. reticulata from C. auratus obtained from a local ornamental fish distributor in Bloemfontein, South Africa (Table 1, Fig. 2D ). Notwithstanding being reported from more than 12 countries ( Martins et al., 2012), it has never been implicated in spillover to native hosts. This is confirmed by the study of Dove and O'Donoghue (2005) who examined 2003 fishes belonging to 33 species from 58 sites in Queensland, Australia, and only found T. reticulata on wild caught C. auratus and another introduced species, the Eastern mosquitofish Gambusia holbrooki Girard, 1859 . Based on current available information, it is most likely that if T. reticulata does get into South Africa's natural waterways it will remain a co-introduced parasite with a low possibility of spillover, however this needs to be further investigated.

3.2.4. Trichodina uniforma

As mentioned above (section 3.2.2), T. uniforma described by Van As and Basson (1989) from C. auratus was originally identified as the invasive T. mutabilis . The same authors further concluded that despite extensive surveys throughout southern Africa, they did not find this species in any other locality other than the original fish farm in the Komatipoort River, which they described it from, nor on any other hosts other than the introduced C. auratus (Table 1, Fig. 2D ). This raised the question as to whether T. uniforma was co-introduced with C. auratus or if it was spillback from its native hosts. Since its description in 1989, various authors have reported this species from (amongst other hosts) C. auratus and C. carpio from their native range in China (see Tang et al., 2007; Qi et al., 2011; Li et al., 2014), thus confirming its status as a co-introduced parasite in South Africa. Recently, Tang and Zhao (2016), using 18S rDNA, supported Van As and Basson (1989) morphological identification of T. uniforma as a separate species to T. mutabilis .

Figures

Fig. 2. Maps indicating the South African distribution records for (A) Lernaea cyprinacea Linnaeus,1758; (B) Argulus japonicus Thiele, 1900; (C) Ichthyobodo necator Henneguy, 1883 (needs molecular confirmation); (D) Trichodina acuta Lom,1961, Trichodina mutabilis Kazubski and Migala,1968, Trichodina reticulata Hirschmann and Partsch,1955, and Trichodina uniforma Van As and Basson, 1989.