Spatial distribution of Monogenean and Myxosporidian gill parasites of Barbus martorelli Roman, 1971 (Teleostei: Cyprinid): The role of intrinsic factors

The gill parasite fauna of Barbus martorelli is much diversified and this raises up the problem of biotope partitioning by these pathogens. The gill colonization analysis of these organisms as well as four distribution gradients: transversal, lateral, longitudinal and vertical was undertaken as a function of the host’s side. The distribution of B. martorelli gill parasites did not reveal any asymmetry in function of the host’s side. The transversal partitioning applied solely to Dactylogyrus insolitus and Myxobolus barbi. The lateral partitioning was inexistent except for D. insolitus which was mostly concentrated on the posterior hemibranch of arch II and Myxobolus njinei which colonized mostly the anterior face of the same arch. The longitudinal partitioning was observed only for M. barbi which mostly encysted into sectors which are more opened to respiratory water current. The vertical partitioning of Monogeneans was subject to the size of their sclerified haptorial pieces; therefore, Dactylogyrus bopeleti and D. insolitus, which are robust, accumulate mostly in the filamentary distal zone whereas Dactylogyrus simplex and Dactylogyrus maillardi, which are weaker, prefer the basal zone. The volume of ventilated water currents and certain intrinsic factors of these fish parasites may determine their spatial gill distribution.