Anostraca

The body of a fairy shrimp is elongated and divided into segments. The body can be divided into three distinct parts (tagmata) – head, thorax and abdomen. The first pair of antennae are small, usually unsegmented, and uniramous. The second pair are long and cylindrical in females, but in males they are enlarged and specialised for holding the female during mating. All but the last two are very similar, with a pair of biramous phyllopods (flattened, leaf-like appendages). The abdomen comprises 6 segments without appendages, and a telson, which bears two flattened caudal rami or "cercopods". Internal anatomy The head contains two digestive glands and the small lobate stomach into which they empty. This is connected to a long intestine, which terminates in a short rectum, with the anus located on the telson. The haemocoel of anostracans is pumped by a long, tubular heart, which runs through most of the animal's length. A series of slits allow haemocoel into the heart, which is then pumped out of the anterior opening by peristalsis. The nervous system consists of two nerve cords which run the length of the body, with two ganglia and two transverse commissures in most of the body segments. Gas exchange is thought to take place through the entire body surface, but especially that of the phyllopodia and their associated gills, which may also be responsible for osmotic regulation. Two coiled glands at the bases of the maxillae are used to excrete nitrogenous waste, typically in the form of urea. Most of the animal's nitrogenous waste is, however, in the form of ammonia, which probably diffuses into the environment through the phyllopodia and gills. ==Ecology and behaviour==

Anostracans inhabit inland waters ranging from hypersaline lakes to lakes that are almost devoid of dissolved substances; they are "the most archetypal crustaceans" in ephemeral waters. The relatively large size of fairy shrimp, together with their slow means of locomotion, makes them an easy target for predatory fish and waterfowl. while the altitude record is held by B. brushi, which lives at in the Chilean Andes. Other genera, such as Streptocephalus, occur in deserts throughout the world. Anostracans swim gracefully by movements of their phyllopodia (thoracic appendages) in a metachronal rhythm. a state of biological dormancy where growth and metabolism are arrested, as an egg (or cyst). This trait assists in both species' dispersal and in overcoming adverse environmental conditions.—as the soft-bodied adults are unable to leave the freshwater system. This inbreeding slows the rate of selection by resisting gene flow and minimizing phenotypic variation, in turn promoting the stability of the existing, successful phenotype. Similarly, Artemia forms an important part of the diet of flamingos wherever it can be found. ==Uses==

: the orange colour is produced by the presence of Artemia. Brine shrimp are used as food for fish and other organisms in aquaria and aquaculture. Their drought-resistant eggs are collected from lakeshores and are stored and transported dry. They hatch readily when submerged in salt water. This is a multimillion-dollar industry, centred on the Great Salt Lake in Utah and San Francisco Bay in California; adults are collected from Mono Lake and transported frozen. ==Fossil record and evolution==

Fairy shrimp are believed to have diverged from the main line of Branchiopoda during the Ordovician period, around the same time it is thought they colonized freshwater and estuarine ecosystems. Some studies point to fossils resembling fairy shrimp in the Upper Cambrian, specifically the oldest known branchiopod fossil, Rehbachiella kinnekullensis, from Orsten marine deposits. Despite its seeming resemblance to modern fairy shrimp, this fossil is still considered by most to be an outlying member of the ancestral marine Branchiopoda rather than an actual fairy shrimp. and the scientific community has reached consensus that Anostraca was the first group to branch off from the Branchiopoda. This suggests that much of the potential habitat in this supercontinent, now occupied by Anostraca, was previously unoccupied by ecologically similar species, or inhabited by species with less adaptive ability. and speciation. ==Diversity==

'' (Branchinectidae) from Georg Ossian Sars' Fauna Norvegiae (1896) Anostraca comprises around 355 species, grouped into 29 genera in eight families: • Artemiidae – 1 genus, 6 species • Branchinectidae – 2 genus, 50 species • Branchipodidae – 6 genera, 35 species • Chirocephalidae – 9 genera, 89 species • Parartemiidae – 1 genus, 18 species • Streptocephalidae – 1 genus, 68 species • Tanymastigidae – 2 genera, 8 species • Thamnocephalidae – 7 genera, 81 species ==Fairy Shrimp in Popular Culture==

Fairy Shrimp has been a student favorite as the mascot of UC Merced. There have been several efforts to make this animal the official mascot of the campus. Still, in 2001 the bobcat was chosen instead. Fairy shrimp had also been the focus of a challenge to the location of where the campus would be built because of their nearby vernal pool habitat. ==References==