Acanthocephalans from fishes and amphibians in Vietnam, with descriptions of five new species

Eight species of acanthocephalans are reported, and five are new. Specimens of Neoechinorhynchus (Hebesoma) manubrianus Amin, Ha & Ha, 2011 were similar to the original description. Neoechinorhynchus (Hebesoma) spiramuscularis n. sp. (Neoechinorhynchidae), from Xenocypris davidi, has a unique proboscis receptacle wrapped in a spiral muscular layer, and an undulating flask-shaped lemnisci, as well as double para-receptacle structures. Heterosentis mongcai n. sp. (Arhythmacanthidae), from Acreichthys sp., has a small fusiform trunk with an unarmed cone and anterior trunk spines, and a proboscis with two circles of rooted apical hooks and 3-4 circles of rooted posterior spines as well as a para-receptacle-like structure at the posterior end. The poorly known Filisoma indicum Van Cleave, 1928 is fully described and illustrated for the first time. Acanthocephalus parallelcementglandatus n. sp. (Echinorhynchidae), from Clarias batrachus, is distinguished from other species of Acanthocephalus by its small fusiform trunk and parallel tubular cement glands. Pseudoacanthocephalus coniformis n. sp. (Echinorhynchidae), from Hylarana sp., is distinguished from other species by having an anterior trunk collar and staggered prominent filiform cement glands, among other features. Cathayacanthus spinitruncatus n. sp. (Rhadinorhynchidae), from Leiognathus equulus, is distinguished from the only two known species of the genus by having a very long and slender proboscis with more than 50 hooks per row and a totally spined trunk. The generic diagnosis of Cathayacanthus Golvan, 1969 is emended. Rhadinorhynchus johnstoni Golvan, 1969 (Rhadinorhynchidae) perfectly fits the only complete description of that species from the Fiji Islands.