Notostraca (redirected from Triopsidae)

Notostraca [nə′täs·trə·kə]

(invertebrate zoology)

The tadpole shrimps, an order of crustaceans generally referred to the Branchiopoda, having a cylindrical trunk that consists of 25-44 segments, a dorsoventrally flattened dorsal shield, and two narrow, cylindrical cercopods on the telson.

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Notostraca 

a suborder of invertebrates of the order Phyllopoda. Almost the entire body is covered with a broad carapace. A pair of closely placed compound eyes and an unpaired simple eye are grouped in the front of the carapace. There are no fewer than 40 pairs of thoracic phylloid appendages, the first two pairs of which are equipped with long filiform tactile processes. The abdomen consists of many segments and ends in a pair of long filiform processes.

The Notostraca inhabit shallow bodies of fresh water that dry up seasonally. They feed on decaying organic remains, plants, and small animals. The females lay eggs into pouches on the 11th appendages and release the eggs on the bottom. The eggs can withstand high and low temperatures in the course of several years. Males are considerably less common than females.

The subphylum embraces nine genera. In the USSR the most common are Lepidurus apus, which measures as much as 12 mm in length, and Triops cancriformis, which measures as much as 7.5 cm in length. Some species serve as food for fish and swimming birds. Others are pests in rice fields, uprooting seedlings and eating shoots.

The Notostraca are considered very old. They have been in existence since the Triassic.

REFERENCES

Beklemishev, V. N. Osnovy sravnitel’noi anatomii bespozvonochnykh, 3rd éd., vols. 1–2. Moscow, 1964.
Zhizrí zhivotnykh, vol. 2. Moscow, 1968.
Dogel’, V. A. Zoologiia bespozvonochnykh, 6th ed. Moscow, 1975.