The cercaria of Galactosomum bearupi Pearson, 1973 (Trematoda : Heterophyidae) at Heron and Masthead Islands, Great Barrier reef, Australia

Magnacercous cercariae, all morphologically identical but with different co loured tails, were found naturally infecting the intertidal prosobranch gas tropod Clypeomorus batillariaeformis Habe & Kosuge (Cerithiidae) at Heron a nd Masthead Islands. Several species of coral-dwelling fishes were exposed to magnacercous cercariae. Active ingestion by the fish, followed by the co mplete development of the metacercaria in the optic lobes, occurred in Poma centrus molluccensis Bleeker, but not in Dascyllus aruanus (L.), where deve lopment stopped short after encystment. All cercariae turned out to belong to the same species, Galactosomum bearupi Pearson, 1973. Natural infections of G. bearupi metacercariae were found in eight species of fish at Heron I sland: Pomacentrus molluccensis, P. wardi Whitley, P. bankanensis Bleeker, P. flavicauda Whitley, Stegastes cf. fasciolatus (Ogilby), Sillago maculata Quoy & Gaimard, S. cf. ciliata Cuvier and Crenimugil crenilabris (Forsskal ). This represents the fourth account of the cercaria of a species of Galac tosomum.