New data on Indo-Pacific pontarachnid mites (Acari: Hydrachnidia: Pontarachnidae), with the description of a new species from Thailand and a new synonymy

In this study, new data on three pontarachnid mite species are reported. A new species, Litarachna samudra sp. nov., is described from the Thai coast of the Andaman Sea. The female of the new species can be distinguished from its closely related congener, Litarachna smiti Pešić, Chatterjee & Ahmed Abada, 2008 from the Red Sea, by the presence of a peg-like medial seta in the dorsal third of P-4 and a high genetic distance estimated at 16.9% (K2P). Two species, Litarachna poliacarus Pešić & Marshall, 2026 and L. bruneiensis Pešić, Chatterjee, Marshall & Pavićević, 2011, are DNA barcoded for the first time. Molecular results revealed that the sequenced specimen of Litarachna bruneiensis from Brunei falls into the cluster of L. almiri Pešić, Smit & Zawal, 2026, a species recently described from Thailand and Mauritius, indicating that these two species are conspecific. It is therefore proposed to consider L. almiri as a junior synonym of L. bruneiensis. The latter discovery suggests a much more continuous distribution than previously hypothesized, indicating that the species likely relies on “stepping-stone” dispersal utilizing the shallow-water tropical corridors and complex coastal currents of the Indo-Malayan Archipelago.