Krill, shrimplike crustaceans that inhabit the open seas. There are more than 90 species, found from the surface of the ocean to a depth of 6,000 feet (1,800 m). Krill are one to two inches (2.5 to 5 cm) long. The body is separated into a thorax and abdomen and is covered by a protective shell called a carapace. Krill feed on plankton and algae. Some species are luminescent. Krill are a source of protein for many marine animals. They are the main food of the baleen whale.Krill are a source of protein for many marine animals.
Krill, like other crustaceans, belong to the class Crustacea of the family Arthropoda. The most common species is Euphasia superba.