Trematodes from Red Sea fishes: Proneohelicometra aegyptensis gen. nov., sp. nov. (Opecoelidae Ozaki, 1925) and Neohypocreadium gibsoni sp. nov. (Lepocreadiidae Odhner, 1905)

Abstract Specimens of the fishes Pterois volitans Linnaeus (Scorpaenidae) and Chaetodon auriga Forsskål (Chaetodontidae) were caught in the Red Sea off the coast of Sharm El-Sheikh, South Sinai, Egypt. Five (20%) and 20 (44%) of these fishes, respectively, were found to harbour intestinal trematodes. P. volitans was parasitised by Proneohelicometra aegyptensis gen. nov., sp. nov. (Opecoelidae) and C. auriga by Neohypocreadium gibsoni sp. nov. (Lepocreadiidae). Proneohelicometra gen. nov. is similar to Neohelicometra Siddiqi et Cable, 1960 which is the only opecoelid genus having caeca opening with separate ani and eggs with unipolar filaments, but differs significantly from it in having two lateral folds of body wall extending along the posterior third of body, an oral sucker smaller than the ventral sucker, a median cirrus sac not reaching the ventral sucker posteriorly and a median genital pore situating immediately posterior to the intestinal bifurcation. Neohypocreadium gibsoni sp. nov. is similar to the other four species of the genus, but is unique in having a distinctly pear-shaped body and a much smaller egg size, and differs significantly from each in several other characters: from N. longisaccatum, it differs in having a cirrus sac not reaching the testes and a pretesticular ovary; from N. dorsoporum in having an external seminal vesicle much shorter than the cirrus sac, a longer cirrus sac extending posteriorly to the level of the posterior margin of the ventral sucker and a pretesticular ovary; from N. chaetodoni in having a smaller body size, symmetrical testes, a longer cirrus sac extending posteriorly to the level of the posterior margin of the ventral sucker and a trilobed ovary; and from N. aegyptense in having a smaller body size, symmetrical testes, a longer cirrus sac extending posteriorly to the level of the posterior margin of the ventral sucker, a trilobed ovary and vitelline follicles terminating anteriorly at the level of oesophagus. Neohypocreadium Machida et Uchida, 1987 is briefly reviewed.