Brine shrimp

Brine shrimp
Artemia salina
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Branchiopoda Order: Anostraca Family: Artemiidae Grochowski, 1896 Genus: Artemia Leach, 1819
Species
Artemia franciscana Artemia gracilis Artemia monica Artemia parartemia Artemia parthenogenetica Artemia persimilis Artemia pollicaris Artemia salina Artemia sinica Artemia tibetiana Artemia tunesiana Artemia urmiana

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.

Overview

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, 1 centimeter), but the giant fairy shrimp Brachinecta gigas can reach over 6 inches (15 centimeters) and is predatory on other fairy shrimp.

Description

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 found in inland saltwaters worldwide, on all continents, in such places as salt lakes and salt marshes. 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.

Artemia is a well known genus as one variety, sometimes identified as a new species, Artemia nyos, or otherwise as simply a cultivated subspecies of Artemia salina, is sold as novelty gifts, most commonly under the marketing name Sea-Monkeys.

Artemia were first discovered in Lymington, England, in 1755. There are mixed views on whether all brine shrimp are part of one species or whether the varieties that have been identified are properly classified as separate species ^{[citation needed]}.

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 cm on average. Brine shrimp have a biological life cycle of one year. This short life span, and other characteristics such as their ability to remain dormant for long periods, have made them invaluable in scientific research, including space experiments.

Brine shrimp can tolerate varying levels of salinity, and 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.

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, as these areas are uninhabitable for potential predators.

The nauplii, or larvae, of brine shrimp are less than 0.5mm when they first hatch. They eat micro-algae, but will also eat yeast, wheat flour, soybean powder, or egg yolk .

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 .

Importance

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).

Brine shrimp have a biological life cycle of one year. This short life span, and other characteristics such as their ability to remain dormant for long periods, have made them invaluable in scientific research, including space experiments.

References

ISBN links support NWE through referral fees

• Grzimek, B., D. G. Kleiman, V. Geist, and M. C. McDade. 2004. Grzimek's Animal Life Encyclopedia. Detroit: Thomson-Gale. ISBN 0787657883.

• "Genus Artemia", The Taxonomicon & Systema Naturae 2000 (listings of taxonomy and scientific classification)
• "Artemia franciscana" Invertebrate Anatomy Online
• "Brine Shrimp and Ecology of Great Salt Lake", United States Geological Survey

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