Antarctic krill, Euphausia superba, is a species of krill found
in the Antarctic waters of the Southern Ocean. It is a small,
swimming crustacean that lives in large schools, called swarms,
sometimes reaching densities of 10,000–30,000 individual animals
per cubic metre. It feeds directly on minute phytoplankton,
thereby using the primary production energy that the
phytoplankton originally derived from the sun in order to
sustain their pelagic (open ocean) life cycle. It grows to a
length of 6 centimetres (2.4 in), weighs up to 2 grams (0.071
oz), and can live for up to six years. It is a key species in
the Antarctic ecosystem and is, in terms of biomass, probably
the most abundant animal species on the planet (approximately
500 million tonnes). Life cycle  The main spawning season of
Antarctic krill is from January to March, both above the
continental shelf and also in the upper region of deep sea
oceanic areas. In the typical way of all krill, the male
attaches a spermatophore to the genital opening of the