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A harpacticoid copepod, Microarthridion littorale (Poppe, 1881), is newly recorded in Korea. Microarthridion species can be distinguished from each other by a combination of the number of the antennular segment, the number of the seta on the antennary exopod, and the armature of the thoracopod legs. Korean materials examined coincide well with M. littorale on these well-known characteristics. However, there are some minor differences in the ornamentations of the maxilliped and swimming legs. The specimens show additional sexual dimorphisms in the setae on enp-3 of P1 and exp-3 of P2-P4. Morphological diversity of so-called M. littorale is also discussed here with detailed features.

Microarthridion littorale (Poppe, 1881) References and records from Norway Tachidius littoralis Poppe, 1881 ��� Scott (1903): 11. Scott (1903) reported this species from the fjord Bogfjorden, Northern Norway, together with T. discipes. He considered M. littorale to be a more brackish-water species than T. discipes., Published as part of Dimante-Deimantovica, I., Jensen, T. C. & Walseng, B., 2016, Freshwater harpacticoids (Crustacea: Copepoda: Harpacticoida) in Norway ��� a comprehensive contribution from G. O. Sars, and a provisional checklist, pp. 1773-1795 in Journal of Natural History 50 (29) on page 16, DOI: 10.1080/00222933.2016.1159348, http://zenodo.org/record/269019

Two new harpacticoid species belonging to the genera Microarthridion Lang, 1944 (Tachidiidae) and Nitocra Boeck, 1864 (Ameiridae) are recorded from underground caves in the karst area of Ninh Binh Province, North Vietnam. Microarthridion thanhi n. sp. is distinguished from congeneric species by the number of setae on the antennary exopod, the structure of leg 5 in both sexes, and the finger-like process modified from an outer distal pinnate seta of the third endopodal segment of leg 2 in the male. Nitocra vietnamensis n. sp. has the character combination of six setae on the ellipsoidal exopod of leg 5 in both sexes, the first endopodal segment of leg 1 shorter than the whole exopod, the seta/spine armature of an inner seta of P2-P4 enp-1 and four elements on P2 enp-3, and the reduction of the proximal endite to a seta on the maxillary syncoxa.