Rediscovery of introduced Korean Semisulcospira from Lake Sotonasakaura, Japan and implication for its identity (Mollusca: Gastropoda)

Assessments of the current status of non-native species and verification of its identity are essential for establishing their impacts on native ecosystems and determining their origins.True taxonomic accounts and recent conditions of non-native Semisulcospira snails introduced into the Tone River system in Japan, which were morphologically identified as "S.cf.forticosta" (Martens, 1886), have not been investigated.We rediscovered living snails of the introduced Semisulcospira snails in Lake Sotonasakaura in the lower reaches of the Tone River system.Although the identities of the most introduced snails could not be determined due to their mitochondrial DNA polymorphisms, molecular phylogenetic analysis confirmed that the population in Lake Sotonasakaura includes true S. forticosta indigenous to South Korea.The centre of its current distribution seemed to be in the lake and the snails may have been brought into the lake along with other non-native freshwater molluscs.The large morphological variation observed in the snails suggests a previously overlooked morphological variation of S. forticosta or the inhabitation of other Korean species in the Tone River system.Thus, further attempts to verify the identity of non-native snails are required, along with assessments of their dispersal and competition with other congeners.