Distribution of Monogeneans of the Genus Ligophorus on Gills of the Soiuy Mullet Planiliza haematocheilus

The distribution on the host gills of three monogenean species of Ligophorus Euzet et Suriano, 1977, parasitizing soiuy mullet Planiliza haematocheilus (Temminck & Schlegel, 1845) in the Black Sea and Sea of Azov was studied. Specimens of L. pilengas and L. llewellyni prefer to localize on the same gill sites, namely, I–III gill arches and their medial sectors. The third species, L. kaohsianghsieni, was distributed on the gills more crowdedly, with about 80% of its specimens being present on II gill arch, occurring on the medial and ventral sectors approximately equally. In general, most monogeneans were found on the largest (in area) and well-watered gill arches and sectors, as well as the anterior hemibranchs; however, within these areas, they preferred to attach to the proximal half of filaments with less amount of water current. The presence of congeners on gills had no significant effect on the distribution of L. pilengas and L. llewellyni. Increasing infrapopulation number resulted in a more uniform distribution of monogeneans on gills; their proportion grew significantly on the faster growing anterior hemibranchs as fish size increased.