Species of Haliotrema Johnston & Tiegs, 1922 (Monogenea: Dactylogyridae) from Zanclus cornutus (L.) (Teleostei: Zanclidae) and Acanthurus nigrofuscus (Forsskål) (Teleostei: Acanthuridae) in the South China Sea.

Four species of Haliotrema Johnston & Tiegs, 1922, including three new taxa, are described from the gills of two species of coral reef fishes, Zanclus cornutus (Linnaeus) and Acanthurus nigrofuscus (Forsskål), off the Dongsha Islands in the South China Sea. Haliotrema dongshaense n. sp., from Z. cornutus, is differentiated from other existing congeneric species by its peculiar male copulatory organ, comprising a harp-shaped copulatory tube and a cup-shaped base, and two groups of short longitudinal muscles lying on either side of the vaginal vestibule. Haliotrema zigmoidocirrus n. sp. from Z. cornutus and H. nigrofusci n. sp. from A. nigrofuscus are differentiated from other congeneric species by their male copulatory organ, which has a cup-shaped base, bell-shaped middle and Z-shaped distal part, and the latter can be readily differentiated from the former by its distinctively wider haptor and longer connecting bars. Haliotrema sicklocirrus Wang, 2007, from Z. cornutus, is redescribed with additional details, including the sinistral position of the accessory piece of the male copulatory organ, the absence of eyespots and the morphology of the connecting bars.