Comparison of Anatomical Characters between Two Subspecies of Trishoplita eumenes

Abstract

Traditional taxonomy of shell-bearing mollusks has generally been dependent on the shell morphology including surface sculpture and color pattern. Nowadays, most researchers also use anatomical information and molecular analysis as the basis of the classification in addition to the shell morphology. In this study, we examined anatomical features in two presumed subspecies of Trishoplita eumenes, land snails distributed in Yamaguchi Prefecture. We then did a statistical comparison of the measured data. The results showed no significant differences between the two in the coloration of the dorsal soft-body, radular morphology, radula formula, jaw-plate morphology or general morphology of the genital system, including the form and microstructure of the penial verge. However, we did find distinct differences in the distribution pattern of black pigments in the dorsal mantle, the ratio of the length of the genitalia to shell diameter, the number of mucus glands, love dart morphology, and the ratio of the length of the love dart to the dart sac. These findings strongly suggest that the two forms represent two distinct species rather than subspecies.