The gut walls and posterior may be orange to dark red in colour, with a prominent lipid sac that is usually red-orange.

[3] Calanus hyperboreus is found in the Arctic, north of the Bering Strait in the Pacific and the Lofoten Islands in the Atlantic.

[3] This copepod spawns between October and March (winter), using lipid-reserves to fuel reproduction (making it a capital breeder[4]).

After the plankton bloom, the eggs develop into stage II and III copepodites and feed actively near the surface from May to October (summer).

[5] In some areas, such as the West Spitsbergen Current, stage V copepodites likely moult (below depths of 500 metres (1,600 ft) to males and females before their third-year of overwintering.

This is likely due to the higher concentration of energy per unit mass of longer chained fatty alcohols and acids.