Thysanoessa raschii

Thysanoessa raschii, sometimes known as Arctic krill, is one of the most common euphausiid species of the sub-Arctic and Arctic seas. They may reach 20–25 mm long, and are sexually mature above 14 mm.

T. raschii is a major prey item of several taxa, including seabirds, planktivorous fishes and marine mammals. On St. Lawrence Island, Alaska, it is the primary constituent of the nestling diet of Crested Auklets (Aethia cristatella), making up about 66% of their diet by biomass between 2000 and 2004. It is also a common prey item of shearwaters and several species of gull.

T. raschii goes through a number of stages in its development. Macdonald defined the characteristics of fourteen stages, or 'furcilia'.