The genetic analysis on the euphausiids from the Antarctic and sub-Antarctic regions showed a large genetic divergence between the Antarctic species E. superba and E. crystallorophias, and the sub-Antarctic one, E. vallentini. The separation occurred around 20 million years ago, which is comparable with the geological time of the formation of the circum-Antarctic water circulation and the Antarctic Polar Frontal Zone (Patarnello et al., 1996).