Novel echinostomatoid trematode (Himasthlidae) parasitising an edible snail, Euspira gilva (Gastropoda), in the East China Sea.

Abstract

A trematode was identified in the gastropod Euspira gilva in the East China Sea. The intensity of infection in individual snails ranged from light to heavy, with an overall prevalence of 83.1% (n = 219). Given the observed decline in the E. gilva population, a series of diagnostic techniques were employed to identify the trematode and investigate the damage caused. These included smear observation, histopathological observation and molecular analysis. The results of the smear observation and histological sections indicated that this trematode only infected the gonad, and the presence of the larval rediae stage in the parasitized tissue was observed. The 28S rDNA sequence was used for molecular identification, which revealed a homology of 92.1-95.8% with the Echinostomatoidea superfamily and a genetic distance of 0.042-0.093 with existing genera within the superfamily. The considerable genetic distance between this trematode and other genera of the superfamily indicates that it cannot be clustered into any genus at present. The phylogenetic tree also demonstrated that this trematode constituted a discrete branch, albeit one that was closely related to Himasthla and Acanthoparyphium spp. within the family Himasthlidae. Based on the aforementioned data and in consideration of the observed decline in wild populations, we postulate that this echinostomatoid trematode represents a potential threat to E. gilva. This is the first report on trematodes in E. gilva.