Morphological and molecular characterization of larval trematodes infecting the assassin snail genus in Thailand.

The assassin snail genus is widespread in Southeast Asia, and is distributed all over the world via the aquarium trade. One species of genus , , is known to act as intermediate host of parasitic trematodes. This study investigates the taxonomic diversity of larval trematodes infecting . and in Thailand. Larval trematodes were identified by combining morphological and DNA sequence data (cytochrome oxidase I and internal transcribed spacer 2). Species delimitation methods were used to explore larval trematode species boundaries. A total of 1107 specimens of sp. were collected from 25 localities in Thailand. Sixty-two specimens of . ( = 33) and . ( = 29) were infected by zoogonid cercariae, heterophyid metacercariae and echinostome metacercariae, with an overall prevalence of 5.6% (62/1107) and population-level prevalences in the range of 0.0-22.3%. DNA sequence data confirmed that the larval trematodes belong to the families Echinostomatidae, Heterophyidae and Zoogonidae. As such, this is the first report of zoogonid cercariae and heterophyid metacercariae in . , and echinostome metacercariae in . . Moreover, this study provides evidence of tentative species-level differentiation between Thai sp. and Cambodian , as well as within , and .