Two new species of Haliotrema Johnston & Tiegs, 1922 (Monogenea: Dactylogyridae) from Acanthurus nigrofuscus (Forsskål) and A. triostegus (Linnaeus) (Teleostei: Acanthuridae) in the South China Sea

Haliotrema nanhaiense n. sp. and Haliotrema triostegum n. sp. are described respectively from the gills of Acanthurus nigrofuscus (Forsskål) and Acanthurus triostegus (Linnaeus) in the South China Sea. Haliotrema nanhaiense n. sp. differs from other existing congeneric species by its male copulatory complex, comprising a C-shaped copulatory tube, a saucer-shaped base and a sickle-shaped accessory piece. Haliotrema triostegum n. sp. can be differentiated from all other members of Haliotrema by having a unique copulatory complex, a cup-shaped base, inverted L-shaped copulatory tube with a small sclerotised piece arising from its distal portion, and a large accessory piece from the proximal portion of copulatory tube.