Elaphoidella longiramus sp. nov. (Copepoda: Harpacticoida, Canthocamptidae), a new species of cave-dwelling copepod from central Thailand.

A new species of harpacticoid copepod belonging to the genus Elaphoidella is described, based on materials collected from Thae Wa Phithak Cave, Lopburi Province, central Thailand. Specimens of Elaphoidella longiramus sp. nov. were found in a water bucket that was fully filled by dripping water from the cave ceiling. Of the 32 Elaphoidella species recorded from Southeast Asia, E. longiramus sp. nov. is the 14th member of this genus reported from Thailand. The new species is most similar to E. thailandensis by having four well-developed setae on the exopod of the female fifth leg. The endopod of the fourth leg is lacking, and the first leg has a two-segmented endopod in both sexes. However, it is distinguished from E. thailandensis by having elongated caudal rami, the exopod with a seta-like spinule on the inner margin of the female fifth leg, a different setal formula on the third exopod of the second to fourth legs, a different number of teeth on the anal operculum, and a different number of ventral spinules on the anal somite.