brine shrimp

brine shrimp

brine shrimp, common name for a primitive crustacean that seldom reaches more than 1/2 in. (1.3 cm) in length and is commonly used for fish food in aquariums. Brine shrimp, which are not closely related to true shrimp, can be found almost everywhere in the world in inland saltwaters, although they are completely absent from oceans. They can live in water having several times the salinity of seawater, but they can also tolerate water having only one tenth the marine salt concentration. Brine shrimp usually occur in huge numbers and can be seen in vast windblown lines in the Great Salt Lake. Their absence from the sea has been explained by their vulnerability to attack by predators and the absence of the latter in their inland saline habitat. Although brine shrimp are considered to be members of a single genus, Artemis, and possibly a single species, there are several varieties. Generally, they have stalked, compound eyes and tapered bodies with a trunk that bears 11 pairs of leaflike legs. Females have a brood pouch from which active young are liberated under favorable conditions. Otherwise eggs are laid parthenogenetically (unfertilized by sperm) or fertilized and can either hatch immediately or be dried and remain viable for many years. These eggs are remarkably resistant to adverse environmental conditions, which is why they can be hatched so easily in saltwater and used for fish food; adult brine shrimp are also used as food in aquariums and are generally sold frozen. Brine shrimp are classified in the phylum Arthropoda, subphylum Crustacea, class Branchiopoda, order Anostraca.

Brine shrimp (Artemia salina)

Any of several small crustaceans (genus Artemia) inhabiting brine pools and other highly salty inland waters throughout the world. A. salina, which occurs in vast numbers in Great Salt Lake, Utah, is commercially important. Young brine shrimp hatched there from dried eggs are used widely as food for fish and other small animals in aquariums. Up to 0.6 in. (15 mm) long, the brine shrimp's body has a distinguishable head and a slender abdomen. It normally swims upside down, and it feeds primarily on green algae, which it filters from the water with its legs.

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Brine shrimp are a species of aquatic crustaceans of the genus Artemia. Artemia, the only genus in the family Artemiidae, have evolved little since the Triassic period. First discovered in Lymington, England, in 1755, Artemia are found worldwide in inland saltwater lakes, but not in oceans.

Artemia is a well known genus as one variety (sometimes identified as a new species Artemia salina x nyos), a cultivated subspecies of Artemia salina, is sold as a novelty gift, most often under the marketing name Sea-Monkeys.

Life cycle

Brine shrimp eggs are metabolically inactive and can remain in total stasis for several years while in dry oxygen-free conditions, even at temperatures below freezing. This characteristic is called cryptobiosis meaning "hidden life" (also called diapause). Once placed in water, the cyst-like eggs hatch within a few hours. The nauplii, or larvae, are less than 0.5mm in length when they first hatch. Brine shrimp have a biological life cycle of one year, during which they grow to a mature length of around one cm on average. This short life span, along other characteristics such as their ability to remain dormant for long periods, has made them invaluable in scientific research, including space experiments.

Diet

Brine shrimp eat micro-algae, but will also eat yeast, wheat flour, soybean powder, or egg yolk.

Tolerance to salinity

Brine shrimp can tolerate varying levels of salinity. A common biology experiment in school is to investigate the effect of salinity levels on the growth of these creatures.

Nutritional benefits

The nutritional properties of newly hatched brine shrimp make them particularly suitable to be sold as aquarium food as they are high in lipids and unsaturated fatty acids (but low in calcium). These nutritional benefits are likely to be one reason that brine shrimp are found only in highly salinated waters with reasonable temperatures. This makes sense as these areas are uninhabitable for potential predators.

'Threatened'

Artemia monica, the variety commonly known as Mono Lake brine shrimp, are found only in Mono Lake, Mono County, California. In 1987, Dr. Dennis D. Murphy from Stanford University petitioned the United States Fish and Wildlife Service to add Artemia monica to the endangered species list under the Endangered Species Act 1973. Despite there being trillions of these creatures in Mono Lake, it was felt that rising levels of salinity and sodium hydroxide concentration of the lake would endanger them because of the increase in pH. However, the US Fish and Wildlife Service reported in the Federal Register on 7 September 1995 that this brine shrimp did not warrant listing after the threat to the lake was removed following a revised policy by the California State Water Resources Control Board.

References

Bibliography

  • Salty Survivors: Artemia: Basic and Applied Biology, Edited by Th. J. Abatzopoulos, J. A. Beardmore, J. S. Clegg and P. Sorgeloos , Kluwer Academic Publishers (2002). ISBN 1402007469

External links

  • http://sn2000.taxonomy.nl/Taxonomicon/TaxonTree.aspx?id=33062 "Genus Artemia", The Taxonomicon & Systema Naturae 2000
  • http://web.archive.org/web/20060423082302/http://www.lander.edu/rsfox/310artemiaLab.html "Artemia franciscana" Invertebrate Anatomy Online
  • http://ut.water.usgs.gov/shrimp/index.html "Brine Shrimp and Ecology of Great Salt Lake", United States Geological Survey

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