The first intermediate host of the invasive frog trematode Glypthelmins quieta in Japan

Glypthelmins quieta is a frog trematode native to North and Central America. This trematode was recently detected in Japan in the American bullfrog Lithobates catesbeianus, which was introduced from North America to Japan. As the first intermediate host of G. quieta, typically a snail, has not yet been identified in Japan, we conducted a snail survey in eastern Japan to screen for an intermediate host using DNA barcoding based on the nuclear 28S ribosomal RNA and mitochondrial cytochrome c oxidase subunit 1. We sampled 3 different snail species, Orientogalba ollula, Physella acuta, and Sinotaia quadrata histrica (157 individuals in total), and only the freshwater snail Physella acuta, which is also believed to have been introduced from North America to Japan, had sporocysts of G. quieta in its hepatopancreas. The introduction of the intermediate and definitive hosts from North America may have facilitated the invasion of G. quieta into Japan.