Branchial monogenean parasites (Monogenea: Dactylogyridae) of fishes from the Okavango River and Delta, Botswana

English: The Okavango Delta has received much popularity for the host of wildlife that it sustains. More recently it has gained increasing interest for the rich diversity of fish species that occur there. The fishes of the Okavango are also becoming increasingly important as a natural resource attracting revenue to Botswana in the forms of ecotourism and aquaculture and also as an important food source for the local community. The Okavango Delta is a flood driven system and much of the fish distribution throughout the Delta and the timing of certain behavioural activities are dependent on the timing and magnitude of the flood. For the purpose of determining the distribution of fish parasites throughout the system, the distribution of the fish hosts was determined and it was found that fish community structure could be used to distinguish different habitat types within the different ecological regions. Fifty-nine of the expected 68 fish species for the Delta have been collected. These species represent 12 families of which the families Cichlidae and the Cyprinidae are the most abundant, making up about 50 percent of the species collectively. Various parasites have been collected from these fishes of which the monogeneans seem to be the most prevalent and abundant and currently represent approximately 36% of the parasites collected. Most of the monogeneans recorded thus far were representatives of the subclass Polyonchoinea. Of these, all belonged to the families Dactylogyridae and Gyrodactylidae. Of the monogenean parasites infesting the Okavango fishes, the representatives of the family Dactylogyridae were the most diverse. Genera of African dactylogyrids are either endemic to Africa or belong to genera with wider geographical ranges. In general dactylogyrids are host specific and their zoo geographical affinities are therefore linked to the faunistic origin of their hosts. The distribution of dactylogyrid species within Africa is determined by the distribution pattern of their hosts. Twenty-two dactylogyrid species comprising seven genera were recorded, of these 10 species were previously undescribed. This study represents the first records of representatives of the class Monogenea from Botswana and hence the Okavango Delta.