Adult digeneans of fishes from the lagoon flats of Palmyra Atoll, Eastern Indo-Pacific, with the description of three new species of the Monorchiidae Odhner, 1911

Abstract Palmyra Atoll is considered a well-conserved and relatively pristine area with high fish diversity. Since digenean trematodes represent one of the most abundant and diverse parasites of marine fish, the aim of this study was to perform taxonomic analysis of adult digeneans in fishes from the intertidal lagoon of Palmyra Atoll. Parasitological analyses were conducted on 653 individual fishes from 44 species collected from the intertidal sand flats, lagoon, and submerged reefs. Along with morphological descriptions of the adult digeneans, we report prevalence, mean intensities, host species, and tissue microhabitats. We identified 306 individual digeneans representing ten species across six families: one enenterid, Enenterum elongatum Yamaguti 1970; one gyliauchenid, Ichthyotrema vogelsangi Caballero & Bravo-Hollis 1952; one lepocreadiid, Diploproctodaeum arothroni Bray & Nahhas 1998; two opecoelids, Opecoelus mulloidichthydis Yamaguti 1970 and Paropecoelus parupenei Yamaguti 1970; one zoogonid, Lecithostaphylus nitens (Linton 1898) Linton 1940; and four monorchiids, Hurleytrematoides coronatus Yamaguti 1970; Sinistroporomonorchis palmyrensis n. sp.; Sinistroporomonorchis crenimugilis n. sp.; and Lasiotocus glossodontae n. sp. The composition of adult digenean species in fishes from Palmyra Atoll’s sand flats shows significant affinities with previously reported for the Eastern Indo-Pacific (EIP) marine ecoregion, specifically Hawaii and the Central Indo-Pacific (CIP), as well as the Great Barrier Reef.