First record of nudibranch mollusk Onchidoris muricata (O. F. Müller, 1776) (Mollusca, Gastropoda, Heterobranchia) in the Sea of Japan and its ephemeral population associated with unusual prey

The nudibranch mollusk Onchidoris muricata known from boreal waters of the western Pacific, North American Pacific shore, and both coasts of the northern Atlantic was first recorded from the Sea of Japan (East Sea). This discovery extends its distribution range southwards along the Asian Pacific coast from cool temperate waters of Kamchatka and Kommander’s Islands to cool temperate sub-zone of the Sea of Japan. Three discovered populations in the northern Sea of Japan are confirmed to be conspecific with other Pacific and Atlantic populations of O. muricata because of external and radular morphology along with low interpopulation genetic variation (