Two new species of protogyrodactylus (Monogenoidea: Dactylogyridae) from the gills of Gerres nigri (Teleostei: Gerreidae) from Senegal

Protogyrodactylus ethiopicus sp. n. and P. kritskyi sp. n. are described from the gills of Gerres nigri Günther (Gerreidae, Perciformes) captured from the estuary of the Sine-Saloum River (Senegal, West Africa). These new species differ from previously described species within the genus by a mid- or dextro-ventral vaginal opening (dextral in all other species). They are part of a morphological species group within Protogyrodactylus Johnston et Tiegs, 1922 that has the tip of the superficial root of the ventral anchor resembling a hook and two anterior projections on the anterior margin of the ventral bar. Protogyrodactylus ethiopicus differs from the remaining species in this group mainly by the morphology of the base of the male copulatory organ (MCO), which is disk-shaped, and the shape of the anterior projections of the ventral bar (round in the new species and relatively elongate in the other species of the group). The other new species, P. kritskyi, differs from all others in the same morphological group in having a MCO with a greatly expanded base that bears a heel-like subterminal sclerotization.