Physical characteristics

Tadpole shrimps are among the largest Branchiopoda, with most species ranging in size from 0.4 to 1.6 in (10-40 mm). Nevertheless, some species may be larger; Triops cancriformis has been reported to reach a length of 4.0 in (11 cm). The head and all the limb-bearing segments of the trunk of tadpole shrimps are covered by a large and shield-like carapace, which is dorsoventrally flattened. They possess a pair of sessile compound eyes on the anterior portion of this carapace just behind a group of two to four ocelli; just behind the eyes there is a nuchal or dorsal organ that may act in chemore-ception. The antennae are reduced or absent. The abdomen is thin, elongated, and flexible with very reduced appendages. The telson bears two long protuberances known as caudal rami. The genus Triops may be easily distinguished from Lep-idurus because the latter possesses an extended supraanal plate on the telson between the caudal rami, while in Triops this plate is reduced or absent. The body of tadpole shrimps is generally pale or translucent, although it may present a pink or reddish coloration due to the presence of hemoglobin in the haemolymph. The carapace varies in color depending on the species, ranging from silvery gray, yellowish, olive, dark brown, and sometimes mottled, rendering them well camouflaged.

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