Diversity of Cladocera and Cyclestherida (Crustacea, Branchiopoda, Diplostraca) in continental waterbodies of southern Vietnam

Microscopic crustaceans, particularly Branchiopoda, often dominate the zooplankton and microzoobenthos of continental waterbodies and are widely utilised in aquaculture as a vital food source for fish and invertebrates. Despite their ecological and economic importance, the knowledge of their diversity and distribution remains highly uneven across the globe. Tropical Southeast Asia, in particular, harbours a rich but, still inadequately documented cladoceran and branchiopod fauna, with many regions remaining largely unexplored or represented only by few historical records. The Republic of Vietnam represents an example of territoty with such knowledge gap: the last comprehensive, systematic survey of its branchiopod fauna was conducted as early as 1980 and, since that time, only fragmented and localised contributions have been added. Consequently, our current understanding of the species richness, biogeographical patterns and environmental drivers in this biodiversity hotspot is severely outdated and incomplete, hampering both fundamental research and applied conservation efforts.To address this gap in current knowledge, we present a new, extensive dataset on samples collected during 2023–2025 in southern Vietnam within the framework of the Joint Vietnam–Russia Tropical Science and Technology Research Center. In total, 476 samples from 360 distinct localities were investigated, covering a wide range of permanent and temporary waterbodies of various types (e.g. ponds, lakes, reservoirs, rice paddies and temporary pools). Sampling was performed using plankton nets and all material was processed at the A.N. Severtsov Institute of Ecology and Evolution following standard hydrobiological protocols. Species identification was based on both recent taxonomic monographs and the extensive expertise of our team, which is internationally recognised as a leader in Southeast Asian Cladocera research. The resulting dataset is published as a Darwin Core Archive in the Global Biodiversity Information Facility (GBIF) and includes, for each sampling event, precise geographic coordinates, date of collection and collector information. This comprehensive, georeferenced resource not only fills a critical geographic and temporal gap in branchiopod biodiversity data, but also provides a solid baseline for future monitoring, biogeographic analyses and assessments of environmental change in the rapidly developing landscapes of southern Vietnam. The dataset contains information on branchiopod zooplankton and microzoobenthos (Branchiopoda, Diplostraca, Cladocera and Cyclestherida) from many permanent and temporary waterbodies in southern Vietnam. The branchiopod communities of the region were poorly known as taxonomy of the group has changed a lot since the latest revision of the local fauna (Thang et al. 1980). Our core data table contains 2415 records belonging to 80 presumptive (76 recognised) species and 45 genera of Cladocera and Cyclestherida from 360 locations. The families Chydoridae with 45 (42 recognised) species from 27 genera and Sididae (nine species from five genera) are the most diverse. No invasive species were found. Results of the current study increase our knowledge about microplankton and microzoobenthos of Vietnam and SE Asia in general.