Artemia salina
sea monkeys

The brine shrimp is found in inland salt water bodies such as the Great Salt Lake in northern Utah, on the rocky coast south of San Francisco, and in the Caspian Sea. They also occur in many other bodies of water with any salt content, including the intermountain desert region of the western United States, salt swamps near any coast, and many man-made saltpans around the world. (Grzimek, 1972; Pennak, 1989)

Artemia salina have a remarkable resistance to change and are able to live in a wide variety of water salinity. All contain some salt content ranging from seawater (2.9-3.5%) to the Great Salt Lake (25-35%), and they can tolerate up to a 50% salt concentration, which is almost saturated. Some are found in salt swamps just inland of the dunes at the seashore, but never in the ocean itself, because there are too many predators. They also inhabit man-made evaporation ponds, used to obtain salt from the ocean. Their gills help them to deal with the high salt content by absorbing and excreting ions as necessary and producing a concentrated urine from the maxillary glands. The temperature of the water also varies greatly from around six to 37 deg C, with the optimal reproduction temperature at about 25 deg C or room temperature. One advantage of their salty location means that they have very few predators, but the disadvantage is their diet is limited. (Banister, 1985)

An adult Artemia salina is usually about 8-10 mm but can reach up to 15 mm depending on its environment. It has an elongated body divided into at least 20 segments and attached to its trunk are approximately 10 sets of flat, leaf-like appendages called phyllopodia that beat in a regular rhythm. The adults can be pale white, pink, green, or transparent and usually live for a few months. They have compound eyes set on stalks and reduced mouthparts.

Artemia salina is in the order Anostroca, literally meaning "no shell," which classifies the shrimp with other species that have no carapace (a hard, bony outer covering). Its subclass Brachiopoda literally means "gill foot," referring to the fact that the gills are on the outer side of the limb bases. (Banister, 1985; Najarian, 1976)

The oddest behavior of A. salina is that they swim up-side down as compared to the majority of aquatic animals. This is a result of positive phototaxis, which means the brine shrimp is attracted to the light, and in nature it is found with its appendages pointed upward, because the sun is the natural light source. A specimen placed on a dissecting scope with a base light source would flip over so that it was swimming "normally." Also, because the brine shrimp are attracted to the light, they rise toward the surface during the day and sink again at night. High intensities of light, however, create a negative phototaxis response and drive the shrimp away. Newborn A. salina demonstrate positive geotaxis, observable when nauplii sink to the bottom after they hatch, because of the effect of gravity.

The same rhythmic movement of the phyllopodia that moves their food anteriorly is the brine shrimp's means of locomotion. They beat their appendages to propel themselves through the water toward the food, without much regard for the rest of the environment. (Grzimek, 1972; Pennak, 1989)

Artemia salina live on photosynthetic green algae, one type is Dunaliella. They obtain food by either filtering small particles with fine slender spines on the legs as they swim or by grazing on bottom mud and scraping algae off rocks with quick movements of their appendages. After the algae is captured, a feeding current moves it anteriorly to the mouth via a central median food groove, utilizing the regular rhythm of the phyllopodia, or leaf-like appendages. (Banister, 1985; Pennak, 1989)

The brine shrimp does not adversely affect humans, because it is not bothersome or poisonous.

Brine shrimp are useful in toxicity tests and for education purposes because they reproduce quickly and their environment is easy to replicate. They are used to teach students the proper technique to observe live specimens and how to design experiments to determine behavior, means of obtaining food, and most optimal environment for reproduction and development.

Both the eggs and adults are used as feed for coral, larval fish and other crustacea, because of their low cost and ease of use. They cost about $7 per pound and their prime selling time is May to July, but they can be produced at any time of year in a laboratory. (Grzimek, 1972)

There is no threat for the brine shrimp, because it reproduces quickly. It is easy to find, and the cost to catch and culture them is low. (Grzimek, 1972)

Artemia salina is the scientific name for Sea Monkeys. These popular, odd looking creatures are advertised as an easy to care for pet that grows quickly and does not have a very long life span.

Brine shrimp are not closely related to the shrimp we eat. One interesting point in their evolution is that their ancestors are fresh-water specimens including the fairy shrimp, which do not adapt well to any change in ions or temperature of the water.

Artemia salina may have become a general name for the many different species. (Banister, 1985)