Morphological and molecular evidence uncovers hidden species diversity in the leatherleaf slug genus Valiguna (Systellommatophora, Veronicellidae) from Thailand

The poorly studied leatherleaf slug genus Valiguna in Thailand was carefully investigated. Members of this genus are phenotypically similar, making their identification very challenging. This study clarifies the taxonomic status of all Valiguna species in Thailand by combining morphological and anatomical studies with DNA barcoding. Monophyly of all Valiguna species was confirmed by analysis of the mitochondrial COI data and that all Valiguna species have the acropleurocaulis type of penis. Currently, three Valiguna species are recognised: V. siamensis, V. semicerina Mitchueachart & Panha, sp. nov., and V. crispa Mitchueachart & Panha, sp. nov. that are new to science. For distinct characteristics, V. siamensis is characterised by having a cylindrical penis and honeycomb-like glans, V. semicerina sp. nov. has a lanceolate penis with half honeycomb-like glans, and V. crispa sp. nov. has a cylindrical penis with wavy-like glans. In addition, more detailed descriptions of the radula and genitalia of all three species and their distribution are also carefully presented, enhancing the understanding of this leatherleaf slug genus in Thailand.