A new species of Mesocyclops [Copepoda: Cyclopoida] from Vietnam

A new freshwater cyclopid, Mesocyclops yenae sp. nov. is described from Central Vietnam. Descriptions of the male, and copepodid stages IV and V are given as well the adult female. Mesocyclops yenae is unique within the genus in having an incompletely sclerotized “pseudosomite” between the pediger 5 and genital double-somite. In the same position, a wholering “pseudosomite” is known in some interstitial copepods only. The conspicously short terminal accessory caudal setae in M. yenae and other similarities in several morphological characters indicate a very close relationship with the Bornean M. brevisetosus Dussart et Sarnita, 1987.