notostracan

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notostracan

(order Notostraca), any member of a small group of crustaceans (class Branchiopoda), composed of the genera Triops and Lepidurus. The approximately 15 known species are strictly freshwater forms, inhabiting lakes, ponds, and temporary pools, chiefly in Europe and North America. The common name tadpole shrimp derives from the animal's distinctive body shape-a large, oval shell-like carapace and a slender, flexible abdomen with a long, forked tail. Extending up to 100 mm (4 inches) in length, the body may have as many as 40 segments, some with several pairs of leaflike appendages. Certain species have up to 70 pairs of limbs. Tadpole shrimp typically dwell at the bottom of bodies of water, feeding on organic debris or preying on small aquatic animals and larvae. Their eggs, which are highly resistant to desiccation, may survive in the soil for many years after temporary pools have dried up; they hatch when the pools have refilled with water.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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