A new species of Tortanus (Atortus) (Copepoda, Calanoida, Tortanidae) from the coastal waters of Nha Trang, Vietnam

A new species of the copepod genus Tortanus, subgenus Atortus, is described from the coastal waters of Nha Trang, Vietnam. The new species is assigned to the tropicus species group sensu Othman (1987) and distinguished from the other members of the group by the morphology of the processes on the fifth pedigerous somite and the genital somite in the female, and the antennule and lea 5 in the male. An analysis of previous records of Atortus indicates highly sporadic occurrence, but a large number of species to be distributed in Southeast Asia. This obviously suggests future discovery of even more species, and also the need for sampling with better geographic and ecological coverage in this particular region.