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.