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Description of Artemia franciscanaSexually dimorphic species. Adult body size is variable, but typically it is about 8 mm in length. The anterior part of the body is not covered by a shield or carapace. The head has a pair of compound eyes at the end of stalks. Head appendages include a short pair of first antennae (also called antennules), a pair of second antennae, mandibles, and paired maxillules and maxillae -- the latter are greatly reduced in size. In males, the second antennae are enlarged and modified as claspers -- in females, they are short and thickened. The body has 19/20 trunk segments. The first 11 trunk segments are classified as thoracic segments and bear paired, paddle-like appendages, also called phyllopods. Posterior to the thorax, there are 7 abdominal segments that bear no appendages. The last body segment bears a pair of long tail filaments. Thoracic appendages are used for swimming and the animal swims ventral side up. During swimming, appendages move in a rhythmic and wave-like pattern, at a frequency of about 5-10 waves per second. Although difficult to see with the naked eye, each wave of movement actually starts out in posterior segments and then, rapidly and sequentially, progresses into more anterior segments. During the power stroke of each cycle of movement, the paddle-like appendages push water in a rearward direction, thus smoothly propelling the animal forward. Importantly, such water currents also function in food gathering, as well as in respiration, since thoracic appendages also have gills. COmmon species in North America, may equate to A. salina.