Taxonomic description of a new freshwater Gammarus (Crustacea, Amphipoda, Gammaridae) restricted to the upper Hantan River, central Korean Peninsula

To date, 12 freshwater Gammarus species are known from South Korea. However, considering the complex topography of the Korean Peninsula, the species diversity of freshwater Gammarus may be underestimated.A new species of the genus Gammarus Fabricius, 1775 is described, originating from the Hantan River region, South Korea.

Gammarus kyungsooki sp. nov. is morphologically characterised by the absence of calceoli on antenna 2, the presence of 6–7 clusters of long setae on the posterior margin of peduncular article 4 in antenna 2, long straight setae along the posterior margins of merus to carpus in pereopod 3, a 0–2–0 dorsal spine formula on urosomite 1, plumose setae on the outer margin of the outer ramus of uropod 3 and three or more clusters of setae on the outer margin of each telson lobe.