Arthropoda

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 : 393

2.3. Phylum Arthropoda

2.3.1. Lernaea cyprinacea

The global distribution of the copepod Lernaea cyprinacea as an invasive ectoparasite, and the severe effects of it on native freshwater fish hosts, has been well documented (see Welicky et al., 2017). Despite the first record of the introduction of this ectoparasite into Africa dating back to the 1960s ( Robinson and Avenant-Oldewage, 1996), it was only recorded for the first time from South Africa twenty years later. Van As and Basson (1984) recognise the unpublished Masters dissertation of Viljoen (1982) as the first document to report L. cyprinacea from South Africa. In addition to Viljoen (1982) records of O. mossambicus and Labeobarbus marequensis (Smith, 1841) from Hartebeespoort Dam in the Crocodile River (West) and Labeo cylindricus Peters, 1852 from the Limpopo River as hosts, Van As and Basson (1984) recorded an infestation of L. cyprinacea on O. mossambicus from the Lowveld Fisheries Station (Table 1, Fig. 2A ). Further confirmation of the presence of L. cyprinacea on South African native fishes was by Van As and Viljoen (1984) and Viljoen (1986) who also reported the presence of L. cyprinacea on O. mossambicus in Hartebeespoort Dam as well as from Labeo congoro Peters, 1852 (syn. Labeo rubropunctatus ) in the Glen Alpine Dam, Mogalakwena River (Table 1, Fig. 2A ).

Interestingly, Bruton and Merron (1985) included L. cyprinacea in their list of what they considered to be doubtful alien species and therefore De Moor and Bruton (1988) did not include this species in their atlas to alien aquatic animals in southern Africa. More than ten years later Robinson and Avenant-Oldewage (1996) increased our knowledge on the distribution and hosts of L. cyprinacea and added another six cyprinid hosts collected from three different rivers (Table 1, Fig. 2A ). These authors also provided a detailed morphological study of L. cyprinacea as well as an updated geographical distribution in Africa. Recently the identity of L. cyprinacea in South Africa was genetically confirmed and two more hosts and three localities where added ( Smit et al., 2016; Truter et al., 2016; Welicky et al., 2017). The most surprising fact regarding the host records of L. cyprinacea in South Africa is that it does not include any of the invasive cyprinids which were potentially responsible for the co-introduction and subsequent co-invasion of this parasite. Globally, the severe effects on native freshwater fish hosts by L. cyprinacea have been well documented; however, the first study on the impact of this co-invader on native fish health in South Africa is the recent work by Welicky et al. (2017). In their paper, the authors reported on the change in host health following a natural drought induced treatment for L. cyprinacea , leaving hosts without this parasite in a much better overall health state than those infected. Future work should include host immune response to infection as well as laboratory based studies on the effect of L. cyprinacea on host fitness.

2.3.2. Argulus japonicus

With a very low host specificity, and one of its hosts from its native range ( C. carpio ) being considered among 100 of the world's worst invasive alien species ( Lowe et al., 2000), it is no surprise that the Japanese fish louse, A. japonicus , is one of the most prevalent and widespread co-invaders in South African freshwater systems. Although reports exist that C. carpio , and its other native host, the goldfish Carassius auratus , were already introduced into South Africa in 1859 and 1726 respectively ( De Moor and Bruton, 1988), the first official record of the co-invading A. japonicus was only in 1983. Kruger et al. (1983) reported it from 11 hosts, including C. carpio , from two sites (Lake Baberspan and Bloemhof Dam) in the Orange- Vaal River system (Table 1, Fig. 2B ). However, it was clear that the introduction of A. japonicus happened much earlier, with Van As and Basson (1984) adding another five hosts and four more localities, including sites from the Crocodile River (West) (Hartbeespoort Dam and Roodeplaat Dam), showing a wide spread occurrence not typically associated with a recent introduction. Van As (1987) supported this and went further by proposing that the records of Argulus spp. by Du Plessis (1952) and Lombard (1968) from the South African Mpumalanga Province were in fact A. japonicus , indicating a much earlier introduction. Following the above reports, additional records of its co-invasion have been published, clearly indicating its wide distribution throughout South Africa ( Fig. 2B ) and successful spillover onto at least nine native hosts ( Avenant-Oldewage, 1994, 2001). Although more recent work on A. japonicus in South Africa focussed on its anatomy, ultrastructure, and reproduction ( Tam and Avenant-Oldewage, 2006; Avenant-Oldewage and Everts, 2010), there are still gaps in our knowledge on the full extent of its distribution throughout South Africa and its impact on native fishes at population and community levels.

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.