Krill facts for kids
Krill are small shrimp-like crustaceans about an inch or so long, found in all the oceans of the world. In areas with nutrients, they occur in huge swarms, with more than 10,000 krill per cubic meter. They feed on phytoplankton and to a lesser extent zooplankton.
Krill are ecologically very important, because they are near the bottom of the food chain. They make up the largest part of the diet of many animals. In the Southern Ocean, one species, the Antarctic krill, Euphausia superba, makes up an estimated biomass of over 500,000,000 tonnes (490,000,000 long tons; 550,000,000 short tons), roughly twice that of the human race.
Most krill are bioluminescent. They have organs called photophores which emit light. The light is made by an enzyme reaction. Krill probably get this substance as part of their diet. Krill photophores are complex organs with lenses and focusing abilities, and can be rotated by muscles. The exact function of these organs is not known. The possibilities include mating, social interaction or as a form of camouflage to compensate for their shadow against the overhead light.
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Krill Facts for Kids. Kiddle Encyclopedia.