Their digestive system is usually visible and this is often a vivid green from the pigment of microscopic plants they have eaten. Krill usually feed on the surface of the water at night and often sink deeper in the water column in the daytime. The primary food of krill is phytoplankton, which are microscopic ocean plants suspended in the upper water column where light is sufficient to allow for growth. Five species There are five species of krill found in Antarctic waters. The most dominant of these species is Antarctic krill, Euphausia superba .
Antarctic krill is one of the most abundant and successful animal species on the planet.
They are frequently found in such abundance that they colour the sea a reddish brown. E superba only grow to about 60mm long and weigh more than a gram, but there is estimated to be about 500 million tonnes of Antarctic krill in the Southern Ocean. Krill are crustacean 'magicians', in that they can continue to change from adults into juveniles. It is estimated that Antarctic krill live for 5-10 years, but determining the age of the animals presents quite a problem for scientists. When the exoskeleton becomes tight again, the moulting and growing process starts once more.