Four new species of genus <i>Acmella</i> W.T. Blanford, 1869 (Gastropoda, Assimineidae) from Southern Thailand.

Abstract

This study explores the diversity of microsnails inhabiting limestone caves in Southern Thailand. It describes four new species of the genus <i>Acmella</i> W.T. Blanford, 1869 (Gastropoda, Assimineidae): <i>Acmella krueangensis</i> <b>sp. nov.</b> from Ranong Province, <i>A. thamsingensis</i> <b>sp. nov.</b> and <i>A. changphueakensis</i> <b>sp. nov.</b> from Chumphon Province, and <i>A. kanchanaditensis</i> <b>sp. nov.</b> from Surat Thani Province. These species are distinguished by shell morphology, particularly the number of striae on the last whorl and the protoconch sculpture. Phylogenetic analyses based on mitochondrial cytochrome c oxidase subunit I (<i>COI</i>) gene sequences further support their distinctiveness and clarify their taxonomic placement. The results enhance the understanding of <i>Acmella</i> diversity in Thailand and shed light on biogeographical patterns found in this genus and the adaptations needed to survive under the conditions of cave systems.