Myxosporean parasites (Myxozoa: Myxosporea) infecting fishes in the Okavango River system, Botswana

[摘要] English: The Class Myxosporea Butschli, 1882 comprises an enormous group of spore formingobligatory parasites that are able to infect any organ of the hosts in which they are found.Myxosporeans mostly parasitise fish and to date there are more than 1300 species knownfrom fishes throughout the world. In Africa, approximately 84 species have been describedfrom primarily freshwater fish. Research on myxosporeans in southern Africa is verylimited, with only a few publications appearing from the coast of South Africa during theearly 20th century. In Botswana no research has ever been conducted on myxosporeanparasites infecting fishes. Botswana contains one of the worlds largest inland delta systemsformed by the Okavango River, which flows in a southeasterly direction from Angola.Knowledge on the fishes as well as their parasites is essential for the well being of a uniquebody of water such as this. Since myxosporean parasites of fish hold the potential to bepathogenic to their hosts and have been known to cause serious economical losses inaquaculture industries throughout the world, it is thus essential to determine the distributionand biodiversity of these parasites in the Okavango River and Delta in Botswana. The mainaims of this project were to investigate the available literature regarding Africanmyxosporeans, compile a database of species infecting freshwater fishes in Africa and toinvestigate the taxonomic status, species biodiversity and prevalence of myxosporeansinfecting fishes in the Okavango River and Delta in Botswana. Fieldwork for this projectwas conducted in June and July 1998 and 1999 in the Okavango and a total of 275 fishesbelonging to 31 species from nine different families were examined for the presence ofmyxosporean parasites. Five myxosporeans from the genus Henneguya Thélohan, 1892were collected from four different fish hosts. Only one of these was identified as a knownspecies and was described in this dissertation. A comprehensive morphological descriptionof the four unknown species was also provided. Eight myxosporeans from the genusMyxobolus Butschli, 1882 were also found infecting nine different fish hosts, of which fourwere identified as known species and described. Detailed descriptions of the four unknownspecies were provided. It was also found that some fish species showed very high gillinfections of these parasites, which may cause some form of respiratory deficiency. Thiscurrent investigation into myxosporean parasites infecting fishes in the Okavango RiverSystem in Botswana provided new insight into the distribution of myxosporeans in southernAfrica and has also opened the door for future research in this unique group.

[发布机构] University of the Free State