Notostraca

Article By:

Fryer, Geoffrey Freshwater Biological Association, Cumbria, United Kingdom.

Last reviewed:August 2020

DOI:https://doi.org/10.1036/1097-8542.457300

An order of branchiopod crustaceans, sometimes called tadpole shrimps. Generally, members of the order Notostraca (see illustration) range from about 10 mm (0.4 in.) to (exceptionally) 90 mm (3.5 in.) in length. The multisegmented trunk, up to 44 segments in some species, is elongate and cylindrical. The anterior part of the body is covered dorsally by a domed carapace, beneath which lie the paired sessile eyes. Each of the first 11 trunk segments bears a pair of limbs, whereas a varying number of more posterior segments bear up to six pairs of smaller limbs per segment—a very unusual situation. At least four, often more, posterior segments are limbless. The trunk terminates in a telson that bears a pair of slender, segmented, caudal filaments. Each trunk limb bears several endites. These are mostly used for handling the food and become progressively reduced on the smaller posterior limbs, but are drawn out into long, filiform sensory structures on the first pair. In the female, the eleventh pair bears a bowl-shaped pouch with a hinged lid that acts as a temporary receptacle for the eggs, which then are shed or are stuck to surfaces. See also: Branchiopoda; Crustacea

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