Great cormorants Phalacrocorax carbo were found dead in a goldfish farm in Aichi Prefecture. They were infected with trematodes in the oral cavity. Based on morphological observation and genetic analysis, the trematodes were identified as Clinostomum complanatum. This is the first case reporting C. complanatum infection of great cormorants in Japan. Heavy metacercarial infection of goldfish was found in the same fish farm. The metacercariae were shown to be the same species as the adult worms from the bird by molecular analysis. These results suggest that great cormorant is involved in the life cycle of this trematode in farmed goldfish.

and can cause mass mortality in farmed fishes (Lo et al., 1981). Mass mortality of goldfish Carassius auratus caused by Clinostomum while high temperature water treatment has been reported (Yasumoto et al., 2018). Infection of C. complanatum also reduces or eliminates the commercial value of ornamental fishes because metacercariae are externally visible as

In 2017, one individual of goldfish Carassius auratus which had tumor-like massive lesions in the skin was found in a goldfish wholesale market in Aichi Prefecture, Japan. The lesions were 2-4 mm in diameter and hemorrhage was observed in some of them. Microscopic observation revealed numerous myxospores with a single polar capsule. The spores were 17.1 ± 1.0 μm (mean ± SD) long, and 6.1 ± 0.7 μm wide. The partial sequence of 18S rRNA gene was 100% identical to that of Thelohanellus testudineus. This is the first report of T. testudineus in goldfish.