Brine shrimp is the common name for any of the small, salinity tolerant, aquatic crustaceans comprising the genus Artemia, the only genus in the family Artemiidae of the order Anostraca (fairy shrimp). They inhabit inland saltwaters, such as brine pools and other highly salty habitats, and are not found in ocean environments.
Despite their small size—adults reaching only about 15 millimeters in length—brine shimp have offer commercial, scientific, and educational values. They are sold as fish food for aquaculture and aquarium hobbyists, used to improve production of salt, and used in scientific and school experiments. One variety is sold as a novelty gift as "sea monkeys." Some are even consumed by people for their nutritional value.
Brine shrimp comprise a genus with the subphylum Crustacea, a group of arthropods (phylum Arthropoda) that includes the familiar crabs, lobsters, shrimps, barnacles, copepods, krill, water fleas, and crayfish. Crustaceans are characterized by having branched (biramous) appendages, an exoskeleton made up of chitin and calcium, two pairs of antennae that extend in front of the mouth, and paired appendages that act like jaws, with three pairs of biting mouthparts. They share with other arthropods the possession of a segmented body, a pair of jointed appendages on each segment, and a hard exoskeleton that must be periodically shed for growth.
Brine shrimp belong to Brachiopoda, one of the several classes of crustaceans that are recognized. Also included in this class are water fleas (Daphnia sp.), and Triops (Notostraca). Within the Brachiopoda, brine shrimp are placed in the order Anostraca, the fairy shrimp. Although fairy shrimp and brine shrimp have the name "shrimp," they are not closely related to shrimp, which are placed in the crustacean class Malacostraca. (Some taxonomies consider Brachiopoda and Malacostraca to be orders.). Most fairy shrimp are small (under ½ inch, one centimeter), but the giant fairy shrimp Brachinecta gigas can reach over six inches (15 centimeters) and is predatory on other fairy shrimp.
Brine shrimp are small members of the fairy shrimp order Anostraca, generally reaching only 0.6 inches (15 millimeters) in length (Gzimek et al. 2004).
As with other fairy shrimp, the brine shrimp's body is distinctly separated into head, thorax, and abdomen. The head consists of two sections—the first one with the antennae and eyes, and the second one bearing the jaws (mandibles and maxillae). The first pair of antennae, known as antennules, are usually of considerable length, but not segmented. The second pair, however, is more muscular, especially in males. The males use their antennae to grasp females while mating. In some males these antennae are equipped with numerous outgrowths and are quite unusual in shape. At the sides of the head is a pair of stalked compound eyes and an unpaired naupliar eye at the top of the head.
Color of brine shrimp varies from nearly hyaline (glasslike, colorless, or transparent) to a bright red (Gzimek et al. 2004). Brine shrimp are filter feeders.
Brine shrimp are found in inland saltwaters worldwide, in such places as salt lakes and salt marshes. For example, they are found in large numbers in Great Salt Lake in Utah, United States. They can inhabit water both many times the salinity of seawater, and also salinities much less concentrated than seawater. However, they are not found in the oceans, with some speculation that this may be due to the heavy presence of predators in the oceans that they do not encounter in inland waters.
While there are several varieties of brine shrimp, there are mixed views on whether these constitute separate species or all are varieties of one species, Artemia salina. Artemia, as Artemia salina, were first discovered in Lymington, England, in 1755, although this particular population is now extinct (Gzimek et al. 2004).
Artemia develop rapidly, with maturation coming slightly over one week after hatching of the nauplius larva (Gzimek et al. 2004). While producing eggs under favorable conditions, some species or strains are viviparious (live birth) and some may reproduce via parthenogenesis.
Brine shrimp eggs are metabolically inactive and can remain in total stasis for several years while in a dry, oxygen-free environment, 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, and will grow to a mature length of around one centimeter on average.
The nauplii, or larvae, of brine shrimp are less than 0.5 millimeters when they first hatch. They eat micro-algae, but will also eat yeast, wheat flour, soybean powder, or egg yolk (Schumann 1995).
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 of 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 September 7, 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 (USFWS 1995).
Brine shrimp have commercial, scientific, and educational values.
The nutritional properties of newly hatched brine shrimp make them particularly suitable to be sold as fish food, as they are high in lipids and unsaturated fatty acids (but low in calcium). Cysts of Artemia are harvested around salt lakes, such as Great Salt Lake in Utah and Kara Bogaz Gol in the Caspian Basin, where they float in large masses, and are hatched to feed fish larvae, either for aquaculture or aquarium hobbyists (Gzimek et al. 2004).
In addition, brine shrimp are known to improve salt production in brine pools and thus are used in commercial salt production (Gzimek et al. 2004).
This short life span of brine shrimp, and other characteristics such as their ability to remain dormant for long periods, have made them invaluable in scientific research, including space experiments. Because 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. They have a rudimentary nervous/spinal system, which leads researchers to believe that they may be used in experiments without concern for animal ethics.
Artemia is a well known genus as a result of one variety—sometimes identified as a new species, Artemia nyos, or otherwise as simply a cultivated subspecies of Artemia salina—being sold as a novelty gift, most commonly under the marketing name sea-monkeys.
In some cases, brine shrimp are used for human consumption, such as the Dawada tribes in Libya's Fezzan desert (Gzimek et al. 2004).
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