Two subspecies of the snail mite Riccardoella (Proriccardoella) reaumuri Fain & van Goethem, 1986 (Acari, Prostigmata, Ereynetidae) from Japan

Riccardoella (Proriccardoella) reaumuri Fain & van Goethem, 1986 has been reported in terrestrial mollusks in France and the Japanese Archipelago. The purpose of this study was to describe two new subspecies of this mite species from Japan based on their morphological characters. Mites were sampled from terrestrial mollusks at 13 locations in Japan from Oct. 16, 2016 to Nov. 13, 2020. The sampled mites and specimens deposited in museum were also used for morphological observations. As a result of principal component analysis (PCA) and cluster analysis based on morphology of dorsal setae on idiosoma and solenidia on palptarsus and tarsus I and II, mite specimens from France and Japan were divided into three groups: Group 1 (mites sampled in France), Group 2 (Okinawajima Is.) and Group 3 (the area from Kyushu Is. to Hokkaido Is.). The solenidia shapes also differed between the groups. We propose that the mites of each of the three groups should be defined as subspecies based on these morphological differences. Our phylogenetic tree of the two subspecies based on amino acid sequences of the mitochondrial cytochrome c oxidase subunit 1 (CO1) confirmed that these Japanese mites are members of the genus, family Ereynetidae.