What is Krill?
{{Taxobox | name = Euphausiacea | image = Meganyctiphanes_norvegica2.jpg | image_caption = Northern krill | regnum = [[Animal]]ia | phylum = [[Arthropoda]] | subphylum = [[Crustacea]] | classis = [[Malacostraca]] | ordo = '''Euphausiacea''' | subdivision_ranks = [[Family (biology)|Families]] | subdivision = * Euphausiidae * [[Bentheuphausiidae]] }} [[File:Krillanatomykils.jpg|thumb|right|230px|Krill anatomy explained, using ''Euphausia superba'' as a model]] '''Krill''' are small [[shrimp]]-like [[crustacean]]s about an inch or so long, found in all the [[ocean]]s of the [[world]]. In areas with [[nutrients]],<ref>Much of the ocean away from the continents is low on nutrients.</ref> they occur in huge [[swarm]]s, 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 (ecology)|biomass]] of over {{convert|500000000|t|lk=on}}, roughly twice that of the human race. They are eaten by many animals, including [[whales]], [[Pinniped|seal]]s, [[penguin]]s, [[bird]]s, [[fish]], [[squid]], and [[whale shark]]s. Of this, over half is eaten by each year, and is replaced by growth and reproduction. Most krill species make large [[vertical]] [[migrations]]. They are distinguished from other crustaceans such as true [[shrimp]] by their externally visible [[gill]]s. == Taxonomy == The order [[Euphausiacea]] is divided into two families, Bentheuphausiidae and Euphausiidae. the first has one species, the second has 85 species. Well known species are the Antarctic krill (''Euphausia superba''), Pacific krill (''Euphausia pacifica'') and Northern krill (''Meganyctiphanes norvegica''). == Bioluminescence == Except for ''[[Bentheuphausia amblyops]]'', krill are [[bioluminescence|bioluminescent]]