Krill: a possible model for investigating the effects of ocean currents onthe genetic structure of a pelagic invertebrate

This paper reviews the information available on the population genetics and systematics of krill (Euphausiidae, Crustacea), integrating the published data with new data collected in our laboratory. Phylogenetic analysis of se veral Antarctic and sub-Antarctic Euphausia species indicates the importanc e of dispersal in determining the present-day geographic distribution. Dati ng speciation events suggest that the formation of the Antarctic Convergenc e, the oceanographic barrier isolating the Southern Ocean, may have played a role in separating the ancestral Antarctic and sub-Antarctic lineages. In traspecific data show that the Antarctic krill (Euphausia superba) is chara cterized by weak genetic differentiation, whereas the northern krill (Megan yctiphanes norvegica) is more structured showing discrete genetic pools. Th is difference can be explained, at least partly, by the oceanographic condi tions in the areas inhabited by the two species.