Anostraca

Anostraca is an order of aquatic crustaceans within the class Branchiopoda. Members are commonly known as fairy shrimps, and those that inhabit highly saline environments are often referred to as brine shrimps, notably the genus Artemia. A defining feature of Anostraca is the absence of a hardened carapace, giving the body a slender, elongated form with numerous swimming and feeding appendages.

Anostracans occupy a wide range of freshwater and saline habitats, including temporary ponds, marshes, prairies potholes, salt flats, and soda lakes. Many species are adapted to ephemeral waters and can undergo rapid life cycles. Artemia, for example, is well known from hypersaline environments and is widely used in aquaculture.

Reproduction in Anostraca varies by lineage. Most species reproduce sexually, but some Artemia populations can undergo parthenogenesis. A notable ecological adaptation is the production of dormant eggs or cysts that resist desiccation and freezing, allowing populations to persist through dry periods and recolonize habitats when conditions improve.

Ecology and human use are intertwined for several anostracan species. They are important primary or secondary consumers in their ecosystems, feeding on microalgae and detritus and serving as a crucial food source for birds and invertebrates. Artemia cysts are harvested commercially as a live feed for fish and crustacean larvae, making these creatures economically significant in aquaculture.

The order includes genera such as Artemia, Branchinecta, Chirocephalus, Streptocephalus, and Thamnocephalus, with a distribution spanning many regions worldwide. The fossil record of Anostraca indicates a long evolutionary history extending back to earlier geological eras.