Some pathophysiological insights into ovarian infestation by Myxobolus sp. (Myxozoa: Myxosporea) in Clarias gariepinus (Clariids: Silurids) from Bénin (West Africa)

Abstract : Mature female specimens of the catfish Clarias gariepinus originating from Ouémé River (Benin) were investigated into ovarian myxozoan parasites. Spores of Myxobolus sp. (Myxozoa: Myxosporea) were found encrusted in the whitish color oocytes which present fat dot aspect in the gonads. The pathological investigation by electron microscopy revealed that maturation and multiplication of spores induced lytic action, deformation and dysfunction of the oocyte internal structures. No host inflammatory reaction was observed, while yolk, lipid, mitochondria, and other oocyte components were degenerated inducing empty area in the oocyte and could lead to castration in case of wide infestation. The mean prevalence was 19.79 %. No significant difference was observed within seasonal prevalence (χ2 = 1.771; df = 3; p > 0.05). Though the host length classes ranging from 35 to 39 cm and 40 to 45 cm were more infected, difference was not significant (χ2 = 2.273; df = 4; p > 0.05) within them. The spores are ovoid in shape with two polar capsules which are equal in size, pyriform, and converging in anterior part of spore with four to five polar filament turns. Spore body are (11.47 ± 0.67) × (8.19 ± 0.52) μm length by width while polar capsule size are (4.24 ± 0.25) × (3.07 ± 0.28) μm and located in the first third portion of the spore. The molecular approaches are still running for accurate identification of this parasite.