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A parasite introduced from Mainland China invades parts of the Tone River system

A collaborative research team from Toho University, the Japan Fisheries Research and Education Agency, Nihon University, the Global Environmental Forum, and the Museum Park Ibaraki Nature Museum has revealed that a newly introduced parasite, bucephalid trematode, is infecting native fish in the Tone River system.

Their study also confirms that the golden mussel, an invasive species, acts as the infection source, while non-native fish such as bluegill and channel catfish help sustain the parasite's life cycle.

This study was in the Journal of Helminthology.

Although previously reported in China, the parasite lacked a valid scientific name. It has now been described as Dollfustrema invadens, marking the second case of an introduced bucephalid trematode in the Tone River system, following Prosorhynchoides ozakii.

D. invadens uses the invasive golden mussel (Limnoperna fortune) as its infection source. It parasitizes native freshwater fish, such as Tridentiger brevispinis and Tridentiger obscurus, as well as non-native freshwater fish, including both domestically and internationally introduced species.

Yellow-colored parasites were observed in the fins and their bases of infected native fish. Notably, high parasite loads were found in infected individuals of the channel catfish (Ictalurus punctatus) and bluegill (Lepomis macrochirus), both of which are designated as invasive species.

These findings suggest that these three invasive species play a crucial role in sustaining the life cycle of the parasite and facilitating its transmission to native fish. This parasite is estimated to have been introduced into the Tone River system around 2020, though its exact introduction route remains unknown. To date, no cases of human infection have been reported.