Anostraca is one of the four orders of crustaceans in the class Branchiopoda; its members are referred to as fairy shrimp. They live in vernal pools and hypersaline lakes across the world, and they have even been found in deserts, ice-covered mountain lakes, and Antarctic ice. They are usually long (exceptionally up to ). Most species have 20 body segments, bearing 11 pairs of leaf-like phyllopodia (swimming legs), and the body lacks a carapace. They swim "upside-down" and feed by filtering organic particles from the water or by scraping algae from surfaces, 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, 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.

thumb|Eubranchipus grubii in an ephemeral pond in a forest in Germany

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

thumb|[[San Francisco Bay Salt Ponds: 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. 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.

  • 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 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