Indriksone J.V., Deart Yu.V., Antokhina T.I., Ekimova I.A.

Nudibranchia is a group of shell-less and strikingly-colored marine molluscs, encountering more than 4000 species. They are distributed worldwide with the highest diversity in the Indo-West Pacific region. Despite there are a lot of researches dedicated to regional fauna composition and distribution, some regions still remain poorly studied. Vietnamese fauna is one of the less studied within the Coral Triangle region. Only three revisions were conducted, and all of them are based on traditional morphological examination and lacks molecular data. Moreover, they were based on material from very restricted areas. To date in total of 150 heterobranch species are registered in Vietnam. At the same time, the biodiversity in adjacent regions (Philippines, Indonesia) is much higher. The main goal of our study was to revise diversity of the suborder Doridina in Southern Vietnam using both modern molecular (COI-based barcoding) and traditional morphological methods. The material was collected in 2016-2019 from Nha Trang Bay and Spratly Islands using SCUBA diving and snorkeling. Of 48 studied species 12 are registered in Vietnam for the first time. All of them were widespread in the Indo-West Pacific, none were endemic. A cryptic diversity was shown within several genera in the family Phyllidiidae, e.g., the species Phyllidiella pustulosa (Cuvier, 1804) includes nine clades, and four of them were recognized in our material. 

Acknowledgments: This study was supported by Russian Foundation for Basic Research grant # 20-34-70044.