Fish myxosporeans from the Okavango Delta, Botswana and the south coast of South Africa

[摘要] English: Myxozoans form a diverse and economically important group of endoparasites thathave been intriguing researchers ever since the early1800's. These parasites arenotorious, having been associated with the devastating effects many species haveshown in aquaculture and fisheries industries throughout the world. Research on bothfreshwater and marine myxosporeans in Africa is limited to a few countries and has,until recently, been largely neglected in southern Africa. In recognition of the need toinvestigate the presence of fi sh-infecting myxosporeans in both the freshwater andmarine environments of southern Africa, a study was initiated in 1997 investigatingthe biodiversity of myxosporeans infecting fi shes in two very unique southern Africanlocalities. Firstly, the Okavango River and Delta in Botswana contains one of theworlds largest inland deltas composed of about 18 000 km2 waterways. Situated inthe middle of the Kalahari Desert, this pristine wetland is the only one of its kind thatforms an inland delta and one of the few river systems in the world that is visible fromspace. The research on myxosporeans infecting marine fi shes was conducted alongthe Cape south coast of South Africa, which has one of the most diverse marine faunaand flora compositions in the world of which 13 % is endemic. This study aimed toreview all existing literature concerning freshwater and marine fish-infectingmyxosporeans in Africa, report on the biodiversity and prevalence of fi sh-infectingmyxosporeans in the Okavango River and Delta, Botswana, investigate the pathogenicpotential of myxosporeans infecting the Okavango fi shes, determine the taxonomicstatus, species biodiversity and prevalence of myxosporeans infecting fi shes along theCape south coast, South Africa and investigate the pathogenic potential ofmyxosporeans infecting intertidal and surf zone fi shes along the Cape south coast ofSouth Afri ca. The examination of 285 8 fi shes representing 14 families and 65 specieson several field trips to the Okavango Ri ver and Delta from 1997 to 2001 revealed thepresence of 29 different fish infecting myxosporeans representing the generaHenneguya Thelohan, 1892 and Myxobolus Btitschli, 1882. Six of these species havebeen described as new in three articles prior to this study. Another two new specieshave been recorded in this thesis, together with the records of 14 miscellaneousspecies that have never been described before, but require more materi al for thecompletion of species descriptions. During the course of nine surveys conductedalong the Cape south coast of South Africa since March 1998, a total of 410 fishes representing 33 species were examined for parasitic infections. Results from thesesurveys revealed the presence of 15 different myxosporean species. Three speciesfrom the genus Ceratomyxa Thelohan, 1892, one species from the genus Henneguya,two from the genus Myxidium Biltschli, 1882, one species from the genus Myxobolusand one species from the genus Sphaeromyxa Thelohan, 1892 are described in thisthesis. Two keys for the identification of both the freshwater, as well as marine andestuarine fish-infecting myxosporeans in Africa are presented as a conclusion to thisstudy. The results obtained from this study have laid the foundation for thecontinuation of research on these parasites in southern Africa and has provided aninsight into the great diversity of myxosporeans infecting southern African fishes.

[发布机构] University of the Free State