Morphological and Molecular Identification of Stellantchasmus dermogenysi n. sp. (Digenea: Heterophyidae) in Thailand

Abstract

We tried a series of morphological and molecular approaches to identify a new species of Stellantchasmus (Digenea: Heterophyidae) originating from the wrestling half-beaked fish, Dermogenys pusillus of Thailand. Adult worm samples of the new species were recovered from hamsters experimentally infected with the metacercariae from D. pusillus in Thailand. Two isolates (Thai and Korean) of Stellantchasmus falcatus were used as comparative control groups. Worm samples of 3 Stellantchasmus groups were morphologically observed and molecularly analyzed with the mitochondrial cytochrome c oxidase 1 gene. The morphological characteristics of S. dermogenysi n. sp. are similar to S. falcatus originating from brackish water fish, but minor difference was noted including the absence of the prepharynx, position of the ovary near the ceca end, smaller body size, and shorter esophageal length. A phylogenetic tree derived from neighbor-joining and maximum-likelihood methods suggests that S. dermogenysi n. sp. is separated from S. falcatus supported by high bootstrap values. The relative divergences persist between these host-specific trematodes, which we suggest should be recognized as 2 distinct species. Comparisons of S. dermogenysi n. sp. with S. falcatus isolated from mullets in Thailand and Korea indicate a genetic divergence of mitochondrial DNA of 19.4% and 21.7%, respectively. By the present study, a new species, Stellantchasmus dermogenysi n. sp. (Digenea: Heterophyidae), is proposed in Thailand based on molecular evidences, in addition to minor morphological differences between S. falcatus and the new species.

Morphological and molecular characterization of larval trematodes infecting the assassin snail genusAnentomein Thailand

“…Moreover, the mean K2P distance between heterophyid species was 23.37% (14.92-31.39%) for COI and 13.65% (2.00-19.66%) for ITS2. Similar COI distances are indicative of species-level differentiation in other heterophyids, such as in the genus Stellantchasmus (Wongsawad et al, 2019), so both the morphological and DNA evidence suggest that the heterophyid metacercariae in this study indeed belong to Heterophyidae. Still, this tentative conclusion needs further corroboration since heterophyid metacercariae are usually found encysted in fish (Waikagul & Thaenkham, 2014) and the family Heterophyidae appeared paraphyletic with respect to the Opisthorchiidae; however, if the assignment of Heterophyidae is correct, then this is the first report of heterophyid metacercariae infecting the snail A. helena.…”

Infections of Digenetic Trematode Metacercariae in Wrestling Halfbeak, Dermogenys pusilla from Bangkok Metropolitan Region in Thailand

“…Many species of fish, including the wrestling halfbeak, garfish (Xenentodon canciloides), mullet (Mugil cephalus), mullet (C. macrolepis), common carp (Cyprinus carpio), and grass carp (Ctenopharyngodon idella) have been reported to be the second intermediate hosts for S. falcatus metacercariae in Thailand, Myanmar, Laos, Cambodia, Korea, and Vietnam [10,17,19,20]. Recently, Wongsawad et al [7] reported that the metacercariae found in the wrestling halfbeak in Chiang Mai province was S. dermogenysi n. sp., which was derived using molecular biology techniques with the mitochondrial cytochrome c oxidase 1 gene.…”

“…[3][4][5][6]. Recently, Wongsawad et al [7] reported Stellantchasmus dermogenysi from wrestling halfbeak, the morphological characteristics of S. dermogenysi are similar to S. falcatus from mullet, Chelon macrolepis, but minor difference was noted including the absence of the prepharynx, smaller body size, and shorter esophageal length. In addition, a phylogenetic reconstruction suggests that S. dermogenysi is separated from S. falcatus.…”