Species identification of introduced veronicellid slugs in Japan

Taxonomic insights and evolutionary history in East Asian terrestrial slugs of the genus Meghimatium

East Asia, specifically the Japanese Archipelago, is a biodiversity hotspot of both vertebrates and invertebrates. Mollusks represent a burst of species diversity in this region due to the effects of biotic and abiotic factors on their morphological traits, such as shell shape and size. However, the evolutionary history of terrestrial slugs in East Asia remains unknown. In the present study, we investigated the molecular phylogeny of terrestrial slugs of the genus Meghimatium. This genus includes three described and eight undescribed species, and our study used all except for two. Based on phylogeny and the species delimitation tests, the genus Meghimatium was split into many putative species, suggesting higher species diversity than previously thought based on morphological and anatomical studies and that almost undescribed species may be inappropriate. Therefore, morphological traits, such as body size and colour, conventionally considered for classification may easily vary or be similar across geographic region. Moreover, the divergence time of this genus is almost concordant with the geographical time scale of the formation of the Japanese mainland. Our findings suggest that molecular phylogenetics helps classify Japanese Meghimatium slugs, but comprehensive taxonomic revisions using multi-locus analyses are needed.

Non-native terrestrial slugs from Sinaloa, Mexico: Deroceraslaeve (O. F. Müller, 1774) and Sarasinulaplebeia (P. Fischer, 1868) (Mollusca, Gastropoda)

This is the first record of two non-native terrestrial slug species from Sinaloa, Mexico. Deroceraslaeve and Sarasinulaplebeia were collected between 2019 and 2022 in Concordia and Mazatlan Municipalities (north-western Mexico). The external morphology and anatomic features of the dissected specimens coincide with the descriptions of each species, whose identities were also confirmed by their partial COI sequences. The ample occurrence of S.plebeia suggests that this species has an established population, while D.laeve was found as isolated individuals, likely associated with plant nurseries.