Antarctic krill [1] ( lat. Euphausia superba ) is an Antarctic pelagic species of crustaceans from the family of euphausiids (Euphausiidae) of the order of euphausians (Euphausiacea).
| Antarctic krill |
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| Scientific classification |
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| No rank : | Bilateral symmetric |
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| International Scientific Name |
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Euphausia superba Dana , 1852 |
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The most widespread species of euphausiids, the dominant phytoplankton , the main link of the food chain in the Antarctic and probably the most numerous species on the planet, whose biomass is estimated at 125 to 750 million tons. It is a valuable commercial species, the annual production of which can reach 500,000 tons. It is circumpolar- antarctic [2] [1] [3] . Antarctic krill also belongs to allochthonous cryopelagic organisms - immigrants, which from time to time may be associated with drifting ice . On the Antarctic shelf in the pack ice zone, it can be found together with subglacial krill ( Euphausia cristallorophyas ) [4] .
Content
One of the largest species of euphausiid. Eye of medium size, spherical. The frontal plate has a rectangular projection above the eyes. Rostrum triangular, short, somewhat shorter in males than in females. The antennula females are more slender than those of the males, in which it is noticeably wider. The lobe of the basal segment of the antenna stem is long and wide (shorter and narrower in males), when viewed from the side it is strongly convex. Abdomen segments without teeth [1] [2] .
The species range is very wide. It is distributed in the waters of the Southern Ocean in a circumpolar manner around Antarctica, from the coastal zone of the continental shelf to the northern boundary of the Antarctic Convergence . The most northern boundary of the species distribution is in the Atlantic sector , where it reaches South Georgia and extends further north, to about 50 Β° S. sh. Usually occurs at depths from the surface to 5β10 m. Performs daily vertical migrations, dropping at night to a depth of 40β50 m. Below this horizon, aggregation of Antarctic krill is rare [1] [2] .
Antarctic krill in the cryopelagic community feeds on diatoms on the underwater ice surface
For Antarctic krill, the formation of very large and dense aggregations, ranging in size from a few meters to 100 kmΒ², is characteristic. The density of such clusters ranges from 0.5 to several kilograms per mΒ³. However, most organisms inhabit the waters of the Antarctic in a rarefied solitary state [1] [2] .
The range of power is quite wide. The main mode of feeding is predation and, to a lesser extent, filtering. It feeds mainly on phytoplankton , mainly diatoms and nano-plankton, both in the water column and from the underwater ice surface, temporarily forming part of cryopelagic communities (see photo). Eats eggs, larvae and adults of dead or living individuals of their own species, as well as other zooplanktophages [1] [2] .
Spawning occurs within the shelf zone or in the open ocean in late spring or summer, with a peak from the beginning of January to the end of February. Spawns in the upper 100-meter layer. Over the next 10 days, the fertilized eggs descend to a depth of 2 thousand meters, hatch as larvae- nauplii and begin to rise to the surface. During the ascent, the phases of development of the larvae from nauplii to metauply and then calyptopus are successively changed. In the surface layers of kalyptopuses, 3 more stages of development pass in their development, turning into furcilia, which in turn have 5 more stages of development, before turning into fry. Each stage of development lasts about 8-15 days [1] [2] .
Life expectancy is up to 6 years.
It is the main food for many fish , penguins , seabirds , pinnipeds and baleen whales .
