Anostraca

Anostraca is on of the four orders of crustaceans that compose the class Branchiopoda, the members of this order are more commonly referred to as "Fairy Shrimp". They swim upside-down and feed by filtering organic particles from the water or by scraping algae from surfaces. They are typically found in vernal ponds and hypersaline lakes (landlocked lakes that contain high levels of sodium chloride and other salts, these saline levels pass that of ocean water) as well as deserts and colder regions such as ice covered mountains. They are an important food source for many birds and fish, and some are cultured and harvested for use as fish food in many regions. There are 300 species spread across 8 families.

Taxonomy

Fairy Shrimp Taxonomy

	Kingdom	Phylum	Subphylum	Class	Subclass	Order
Classification	Animalia	Arthropoda	Crustacea	Branchiopoda	Sarsostraca	Anostraca

Description

A Fairy Shrimps' body is typically elongated and divided into multiple sections, these sections are typically divided into three distinct parts: head, abdomen, and thorax. The whole animal can typically measure anywhere from .25 - 1 inch long (6-25 millimeters), however some species may not even reach sexual maturity until they are 2 inches (50mm) long with the ability to grow up to almost 7 inches (170 mm). Fairy shrimp possess a thin but flexible exoskeleton that unlike that of other arthropods do not have a carapace(an upper section of exoskeleton found in many groups of animals).

The head of Fairy Shrimp are distinct from the thorax in that the head possesses two compound eyes and then two separate pairs of antennae. The shape of the second pair of antennae differ between male and females of the species in that the males second pair of antennae are enlarged and specialized (instead of long and cylindrical) in order to be able to better hold females during mating.

When it comes to the thorax most members of this order have 13 segments with the exception of Polyartemiella and Polyartemia which possess 19 and 21 respectively. All segments but the last two are similar in that they have a pair of flattened leaf-like appendages. The last two segments of the body are fused together and the appendages are then specialized for sexual reproduction. Most anostracans have separate sexes, however a few reproduce by parthenogenesis.