The African monogenean gyrodactylid genus Macrogyrodactylus Malmberg, 1957, and the reporting of three species of the genus of Clarias gariepinus in South Africa.

Three different species of the genus Macrogyrodactylus Malmberg, 1957, collected from the gills and skin of Clarias gariepinus (Burchell, 1822) from the Middle Letaba Dam and Mokgoma-Matlala Dam in South Africa were examined and identified. This is the first record of a species of the genus in South Africa. The three species are M. congolensis (Prudhoe, 1957)--found on the skin, M. clarii Gussev, 1961 and M. karibae Douellou & Chishawa, 1995--found on the gills. The last species is elevated to the status of a species having been described previously as a subspecies of M. congolensis. The present study presents and discusses the value of some of the taxonomic characters which can be used to differentiate the species of the genus. The shape and size of the sclerites of the haptor are found to be the most reliable characters. Only four species of the genus, namely M. polypteri and the three above-named species are regarded to be valid. Three species, namely M. latesi Paperna, 1969, M. anabantii Paperna, 1973 and M. ctenopomii Paperna, 1973 are regarded as species inquirenda. Generic diagnoses, measurements and illustrations of the sclerites of the four valid species are presented and a key for their differentiation is provided. The development of the gyrodactylid population on C. gariepinus during the filling of the Middle Letaba Dam in South Africa is discussed.