A new species of Bivesiculoides (Digenea: Bivesiculidae) infecting atherinid fishes of the Great Barrier Reef, Queensland, Australia.

We describe a new species of Bivesiculidae, Bivesiculoides maiae n. sp., from Hypoatherina tropicalis (Whitley) (Atherinidae) collected from off Heron Island (southern Great Barrier Reef, Queensland, Australia). Bivesiculoides maiae n. sp. is morphologically consistent with Bivesiculoides Yamaguti, 1938 in the entirely pre-testicular position of its uterus, and the possession of caeca and vitelline fields that extend posteriorly to level with the anterior extremity of the testis. The new species is morphologically distinct from the six known Bivesiculoides species in body size and shape, and shape of the pharynx and testis. Bivesiculoides maiae n. sp. is genetically distinct from the only other sequenced Bivesiculoides species, Bivesiculoides fusiformis Cribb, Bray & Barker, 1994, with which it occurs sympatrically at Heron Island. A review of related species allows two systematic recombinations. In view of the pre-testicular position of its uterus, we recombine Bivesicula hepsetiae Manter, 1947 as Bivesiculoides hepsetiae (Manter, 1947) n. comb. In view of its obtriangular body shape, round pharynx, strongly elongated testis, and the position of its ovary opposite the testis, we recombine Bivesiculoides triangularis Machida & Kuramochi, 2000 as Treptodemoides triangularis (Machida & Kuramochi, 2000) n. comb. Host-specificity of species of Bivesiculoides and their geographic distributions are discussed.