Spatial distribution of monogenean gill parasites of Parachanna obscura (Günther, 1861) – Channidae – in Lake Ossa (Edéa, Cameroon)

Abstract

Parasites are a danger for fish even more in natural environment than in farming conditions. Knowledge of their biology of is important for prevention. The objective of this study was to investigate the distribution of monogenean gill community of Parachanna obscura (Pisces, Channidae). Monogenean species were identified using the morphology of haptoral and genital sclerotized parts. Appropriate statistical tests were used to compare prevalence and intensity of parasites. In Lake Ossa (south Cameroon), P. obscura individuals were in relatively good condition (K = 1,4±0,15) although they were infected by five monogenean species ( Eutrianchoratus magnus , E. minutus, E. imbachi, E. chibami and E. malleus ). Male and female fish harbor similar parasite intensity. There was not statistical difference in the infection patterns of different host sizes, although big or old fish seemed to accumulate parasites over time. The distribution of helminthes on the gills did not revealed host side preference. There is no evidence of competition between species of Eutrianchoratus in their distribution areas, but the filaments of different gill arches exert a progressive (antero-posterior) sifting effect on the infecting larvae. This study proves once again that in natural environment parasite intensities are very low or low and this state minimizes competition between monogeneans species. Keywords : Ancyrocephalidae, Eutrianchoratus , sifting effect, prevalence, intensity, fish.