Authors

M Truter²; A A Acosta²; O L Weyl¹; N J Smit²;  ¹ South African Institute for Aquatic Biodiversity, South Africa;  ² Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa

Discussion

The viviparous genus Macrogyrodactylus Malmberg, 1957 is an endemic group of Monogenea parasitic on fish from Africa. The genus consists of nine species, primarily parasitising the skin and gills of freshwater catfishes (Clariidae).  Interest in this parasitic genus was driven by its pathogenic potential, first noted in aquaculture conditions and later in natural habitats. To date three species, Macrogyrodactylus clarii, M. congolensis and M. karibae have been recorded from the pan-African distributed African sharptooth catfish Clarias gariepinus. It is also suggested that these three species have a specificity or affinity for C. gariepinus as a host. More recently, based on morphological and molecular analyses a so-called hybrid species, Macrogyrodactylus clarii x M. heterobranchii was observed from two African countries. 

In southern Africa C. gariepinus is predominantly a native species, however it has been translocated to freshwater systems in the Eastern and Western Cape provinces of South Africa. During the present study 184 individuals of C. gariepinus were collected from various localities in Zambia and South Africa and was subjected to a parasitological screening. Infestation of the skin, fins and gills with M. clarii, M. congolensis and M. karibae were found with a Prevalence of 64–100% and infestation intensity of 1–109 per individual host. Co-occurrence of the three species differed between native distribution localities and co-introduction of Macrogyrodactylus spp. did not occur to the freshwater systems in South Africa where C. gariepinus is invasive. Morphological observations, their phylogenetic position, using the entire ITS-1 and ITS-2 regions, and new locality records for all three species are presented.

This study also reviewed the distribution of Macrogyrodactylus spp. from C. gariepinus in Africa and i) revealed support for preference or affinity of three Macrogyrodactylus spp. toward C. gariepinus; ii) the ecology of Macrogyrodactylus spp. is understudied and iii) highlight the disparity in parasitological surveys and records in Africa where at least 78% of African countries have no freshwater fish parasitology data, even from a host as widely distributed and utilised as C. gariepinus.

Keywords: fish parasites, endemic species, phylogeny