Paradiscogaster flindersi and P. oxleyi n. sp. (Digenea: Faustulidae): overlapping host and geographical distributions in corallivore chaetodontid fishes in the tropical Indo-west Pacific

A total of 2,868 individuals of 47 species of chaetodontids were examined for faustulids at seven major localities in the Tropical Indo-West Pacific (TIWP). Combined morphological and molecular analyses allowed us to describe Paradiscogaster oxleyi n. sp. from three localities in the TIWP and in three host species, Chaetodon lunulatus Quoy & Gaimard (type-host), C. ornatissimus Cuvier and C. meyeri Bloch & Schneider. Molecular analysis of the ITS2 region of rDNA from two host species and three localities supports the morphology-based conclusion that P. oxleyi n. sp. is the same species at the three localities. Paradiscogaster flindersi Bray, Cribb & Barker, 1994 is reported from three new localities in the TIWP and is now known from 13 chaetodontid species. Sequences from samples consistent with P. flindersi differed from those from P. oxleyi n. sp. in 11–12 base pairs. The host ranges of the two species overlap broadly. Neither species was found in French Polynesia but both were found at Swain Reefs on the Great Barrier Reef. Only one of the two species was found at each of the five other sites. Both species occur almost exclusively in specialist corallivores allowing the inference that the metacercariae occur in corals. Finally, a key to the species of Paradiscogaster is provided.