2018 Volume 76 Issue 1-4 Pages 1-18
The Recent species of the genus Volutharpa in Japanese and adjacent waters are reviewed based on the morphology of the shell, operculum, penis and radula, as well as their geographical distribution. The genus is provisionally distinguished from the allied genus Buccinum based on the differences in the general morphology of the shell. Five operational taxa are recognized, and compared with each other. The morphology of the penis, especially the gonopore, and of the periostracum were found to be most valuable in distinguishing species and subspecies within the genus. Radula characters, including the number of cusps, were shown to be variable even within species, and not suitable for species-level classification. Three discontinuous morphotypes were recognized in the shape of the gonopore, and these were considered to represent three species groups: 1) papillary type: ampullacea; 2) triangular type: nipponkaiensis species group comprising nipponkaiensis and limnaeformis; and 3) pointed type: perryi species group comprising perryi and ainos. Furthermore, two taxa in each species group were morphologically distinguished by the condition of the periostracum, and distinguished as subspecies. The subspecific distinction of limnaeformis and ainos are also supported by their allopatric distribution with corresponding nominotypical subspecies. As a result, the genus Volutharpa in Japanese waters is revised to comprise three species and two subspecies.