We found Anemina species in a canal in Yaizu City, Shizuoka Prefecuture, central Honshu, Japan. In this paper, we attempt to determine its taxonomic position by means of molecular phylogenetic analysis and morphological observation. The shell morphology of Anemina sp. matches well that of Anemina euscaphys (Heude, 1879), which was described from the lower Yangtze River basin of China. In the molecular phylogenetic analysis, however, Anemina sp. clustered with the reference sequences of not only Anemina euscaphys but also Anemina arcaeformis (Heude, 1877) and Anemina globosula (Heude, 1879) so that we could not determine which species it belongs to. Anemina sp. is known to occur in China, South Korea and northern Kyushu Island in Japan, and this is the first record from Honshu Island. It was found in a canal flowing from eel farms (Anguilla japonica) in Shizuoka Prefecture, so it was possibly introduced from elsewhere together with imported juvenile eels ("glass eels"). On the other hand, there is also a possibility that Anemina sp. in Shizuoka Prefecture is indigenous and has until now been confused with other similar species [e.g., Sinanodonta lauta (Martens, 1877), Beringiana japonica (Clessin, 1874) or Beringiana fukuharai Sano, Hattori & Kondo, 2020].

Scapharca broughtonii (Schrenck, 1867) and S. aff. broughtonii have been recovered for the first time from the upper Pliocene (Piacenzian) deposits on the Japan Sea side of Honshu. This is the oldest record of S. broughtonii and its related species. S. satowi is known from the same locality as S. broughtonii in the upper Pliocene Tentokuji Formation in Akita Prefecture, Japan Sea side of northern Honshu. These fossils suggest that the genetically similar ark shells speciated near the northern limit of the warm-water current in the semi-enclosed Japan Sea by the late Pliocene. In the middle Pleistocene (Chibanian), S. broughtonii first adapted to cold-temperate water, being known from the Dateyama Formation on the Japan Sea side of central Hokkaido and associated with many cold-water and a few temperate-water species.

We observed sphaeriid clams attached to the digits of salamanders distributed in wetlands of eastern Hokkaido, Japan. One of the clams in either the genus Euglesa or Odhneripisidium was found on a salamander (Salamandrella keyserlingii) captured on dry land, showing that the clam was being transported by a land-walking amphibian. It is possible that sphaeriid clams migrate between water areas using salamanders to expand their distribution.