Құбыршақты шаяндар: сипаттамасы мен тіршілік ортасы

Order of crustaceans

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, with the exception of Branchinecta gigas, or "giant fairy shrimp", which is itself a predator of other species of anostracans. They are an important food for many birds and fish, and some are cultured and harvested for use as fish food. There are 300 species spread across 8 families.

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, 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.