Artemia is a genus of aquatic crustaceans known as brine shrimp. Artemia, the only genus in the family Artemiidae, has changed little externally since the Triassic period. The historical record of the existence of Artemia dates back to 982 from Urmia Lake, Iran. Artemia populations are found worldwide in inland saltwater lakes, but not in oceans. Artemia are able to avoid cohabitating with most types of predators, such as fish, by their ability to live in waters of very high salinity up to 250%.
There are seven known species of Artemia:
7.Artemia urmiana which is found in Urmia Lake ,Iran.
The ability of the Artemia to produce dormant eggs, known as cysts, has led to extensive use of Artemia in aquaculture. The cysts may be stored for long periods and hatched on demand to provide a convenient form of live feed for larval fish and crustaceans. Nauplii of the brine shrimp Artemia constitute the most widely used food item, and over 2000 tonnes of dry Artemia cysts are marketed worldwide annually. In addition, the resilience of Artemia makes them ideal animals for running biological toxicity assays and is now one of the standard organisms for testing the toxicity of chemicals. A breed of Artemia is sold as a novelty gift under the marketing name Sea-Monkeys.
The brine shrimp Artemia comprises a group of eight species very likely to have diverged from an ancestral form living in the Mediterranean area about 5.5 million years ago.
Artemia is a typical primitive arthropod with a segmented body to which is attached broad leaf-like appendages. The body usually consists of 19 segments, the first 11 of which have pairs of appendages, the next two which are often fused together carry the reproductive organs, and the last segments lead to the tail. The total length is usually about 8 millimetres (0.31 in)-10 millimetres (0.39 in) for the adult male and 10 millimetres (0.39 in)-12 millimetres (0.47 in) for the female, but the width of both sexes, including the legs, is about 4 millimetres (0.16 in).
The body of Artemia is divided into head, thorax, and abdomen. The entire body is covered with a thin, flexible exoskeleton of chitin to which muscles are attached internally and shed periodically. In female Artemia a moult precedes every ovulation.
For brine shimp, many functions, including swimming, digestion and reproduction are not controlled through the brain; instead, local nervous system ganglia may control some regulation or synchronization of these functions. Autonomy, the voluntary shedding or dropping of parts of the body for defense, is also controlled locally along the nervous system. Artemia have two types of eyes. They have two widely separated compound eyes mounted on flexible stalks (image1). These compound eyes are the main optical sense organ in adult brine shrimps. The median eye, or the naupliar eye, is situated anteriorly in the centre of the head and is the only functional optical sense organ in the nauplius, which is functional until the adult stage.
Ecology and behaviour
Brine shrimp can tolerate varying levels of salinity from 5‰ to 250‰, and occupy the ecological niche that can protect them from predators. The preferred level of salinity is about 30–35‰. Locomotion is achieved by the rhythmic beating of the appendages acting in pairs. Respiration occurs on the surface of the legs through fibrous, feather-like plates (lamellar epipodites).
An Artemia cyst
In their first stage of development, Artemia nauplii do not feed but consume their own energy reserves stored in the cyst. Wild brine shrimp eat microscopic planktonic algae. Cultured brine shrimp can also be fed particulate foods including yeast, wheat flour, soybean powder or egg yolk.
Adult female brine shrimp ovulate approximately every 140 hours. In favourable conditions, the female brine shrimp can product eggs that almost immediately hatch. While in extreme conditions, such as low oxygen level or salinity above 150‰, female brine shrimp produce eggs with a chorion coating which has a brown colour. These eggs, also known as cysts, are metabolically inactive and can remain in total stasis for two years while in dry oxygen-free conditions, even at temperatures below freezing. This characteristic is called cryptobiosis, meaning "hidden life". While in cryptobiosis, brine shrimp eggs can survive temperatures of liquid air (−190 °C or −310.0 °F) and a small percentage can survive above boiling temperature (105 °C or 221 °F) for up to two hours. Once placed in briny (salt) water (>5‰), the eggs hatch within a few hours. The nauplii, or larvae, are less than 0.4 mm in length when they first hatch. Brine shrimp have a biological life cycle of one year.
NASA Scientists have taken the eggs of brine shrimp to outer space to test the impact of radiation hazard to life. The eggs traveled on Apollo 16 to the moon and back. The cosmic ray passed through an egg would be detected on the photographic film in their container. In one experiment, some eggs were kept on Earth as experimental controls to ensure a fair test. Also, as the take-off in a spacecraft involves a lot of shaking and acceleration, one control group of egg cysts was accelerated to seven times the force of gravity and vibrated mechanically from side to side for several minutes so that they could experience the same violence of a rocket take-off. There were 400 eggs in each experimental group. All the egg cysts from the experiment were then placed in salt water to hatch under optimum conditions. As a result, a high sensitivity to cosmic radiation was observed on Artemia salina eggs; 90% of the embryos, which were induced to develop from hit eggs, died at different developmental stages.