Distribution of Gill Parasites of the Freshwater Fish Barbus martorelli Roman, 1971 (Teleostei: Cyprinidae) and Tendency to Inverse Intensity Evolution Between Myxosporidia and Monogenea as a function of the Host Age

Abstract

The study of gill parasite fauna from 558 Barbus martorelli in a tropical freshwater course near Yaounde (Cameroon) was undertaken to collect data on the distribution of pathogens in a wild population, which is essential to find means of avoiding catastrophic losses often observed in intensive aquaculture. The analysis revealed the presence of two myxosporidian species (Myxobolus barbi and M. njinei) and eight monogenean species (Dactylogyrus bopeleti, D. insolitus, D. simplex, D. maillardi, Dogielius martorellii, Dogielius sp., one species of Gyrodactylidae and one larva of Polystomatidae). Four individual fish were found without parasites, whereas 24 and 530 presented monospecific and multispecific infections, respectively. Each infested host harbored an average of four parasite species. As the prevalence and mean intensity reduced with the host size for protozoans, the reverse phenomenon was observed for helminths. A sexual effect was observed on the infestation of B. martorelli by the myxosporidian M. njinei and by most monogenean species; females were thus more infested than males due to the biology of gravid specimens. Finally, the high parasite species richness appeared to reduce the host weight.