A review of the genus Antorchis Linton, 1911 (Trematoda: Faustulidae) from Indo-Pacific fishes with the description of a new species.

Species of the faustulid genus Antorchis Linton, 1911 of the tropical Indo-West Pacific are reviewed. We recognise five species in the region, including a novel form. Antorchis nasonis n. sp. is described from Naso annulatus (Quoy & Gaimard) and N. tonganus (Valenciennes) on the southern Great Barrier Reef (GBR). We interpret specimens reported from Naso hexacanthus (Bleeker) from Japan as the same species. This species appears to be the only faustulid known from acanthurid fishes and differs from all other species in the genus in having the prominent dorsal genital invagination close to the posterior end of the body. In addition, new host and locality records are reported for two described species of Antorchis, A. pomacanthi (Hafeezullah & Siddiqi, 1970) and A. tsushimaensis (Machida, 1971). The wide distribution of A. pomacanthi was further demonstrated by the generation of identical ITS2 rDNA sequences for specimens from Ningaloo Reef off Western Australia, off Lizard and Heron Islands (GBR) and off New Caledonia, localities separated by up to 5,300 km. The host-specificity of the genus is considered.