Genetic differentiation in the Antarctic coastal krill Euphausia crystallorophias.

The population genetics of the Antarctic neritic krill species Euphausia crystallorophias was examined by nucleotide sequence variation in its mitochondrial DNA. A 616 base pair region of the cytochrome c oxidase subunit I (COI) gene was screened for mutations by single-strand conformational polymorphism (SSCP) combined with restriction digestion. E. crystallorophias caught in three different regions of the Antarctic coastline were used--two samples from the Mertz Glacier Polynya and one sample each from the western side of the Antarctic Peninsula and from the Davis Sea. Significant genetic differences between krill samples were identified. However, the extent of these differences did not correlate with the degree of geographic separation between the sampling sites. This suggests that the genetic structuring may be the result of small-scale differentiation rather than differentiation between resident populations in separate parts of the Southern Ocean. The possibility that genetic differences between samples within a region are as important as differences between regions has implications for other studies of krill population genetics.