New and rare species of water mites (Acari: Hydrachnidia) from interstitial waters of Hainan Island, China

This study presents the first survey of water mites from interstitial waters on Hainan Island, China, using the Karaman-Chappuis method. Two new species are described, Hygrobates (s. s.) xiaoqingi sp. nov. and Kawamuracarus jini sp. nov., together with a supplementary description and the assessment of the intraspecific variation for Kawamuracarus goldschmidti Li, Smit, Jin & Guo, 2025. Detailed morphological descriptions, micrographs, and morphometric data are provided. The new species exhibit typical interstitial adaptations, e.g. small eyes, flattened idiosoma and the absence of swimming setae. This work fills a gap in the taxonomic knowledge of Chinese hyporheic water mites, and provides essential baseline data for understanding the biodiversity and conservation of groundwater-influenced ecosystems.