Host-parasite associations on a coral reef: pomacentrid fishes and digenean trematodes.

A comprehensive survey of 39 sympatric species from the Pomacentridae from the southern Great Barrier Reef revealed 18 species of digenean trematodes. Individual species of trematodes infected between one and 24 species of pomacentrids. Overall, host specificity was low, indicating host switching during the evolution of associations among these hosts and their parasites. Factors which may have facilitated host switching are discussed.