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Results for Leptostraca
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(invertebrate zoology) A primitive group of crustaceans considered as one of a series of Malacostraca distinguished by an additional abdominal somite that lacks appendages, and a telson bearing two movable articulated prongs.
The only extant order of the crustacean subclass Phyllocarida. The Leptostraca is represented by one fossil and a small number of living genera. These malacostracans are unique in having the carapace laterally compressed to such an extent that it forms a bivalvelike shell held together by a strong adductor muscle. The carapace covers only the thorax, leaving exposed the head, with its uniquely movable rostrum, stalked eyes, paired antennules, and antennae.
Leptostracans use the thoracopods to produce a feeding current and, in females, to form a brood pouch. That secondary brooding function suggests that egg-bearing females generally do not feed. Locomotion in leptostracans is accomplished by use of the first four pairs of pleopods. Most leptostracans are bottom dwellers, living on or slightly under the substrate, but one species is holopelagic, one inhabits hydrothermal vents, and still another is a marine cave dweller. See also Crustacea; Phyllocarida.
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 Nebalia bipes
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Nebaliidae |
Leptostraca (from the Greek words for thin and shell [2]) is an order of small, marine crustaceans. Its members, including the well-studied Nebalia, occur throughout the world's oceans and are usually considered to be filter-feeders [3]. It is the only order in the class Phyllocarida.
Leptostracans are usually small (typically 5–15 mm long [4]) possess a head with stalked compound eyes, two pairs of antennae (one biramous, one uniramous) and a pair of mandibles but no maxillipeds [3]. The carapace is large and comprises two valves which cover the head and the thorax, including most of the thoracic appendages, and houses as a brood pouch for the developing embryos. The abdomen has eight segments, six of which bear pleopods, and a pair of caudal furcae, which may be homologous to uropods of other crustaceans [5].
It is now accepted that leptostracans belong to the Malacostraca [6], and the sister group to Leptostraca is Eumalacostraca [7].
The Order Leptostraca is divided into three families, with ten genera containing a total of around 39 valid described species [8]:
Nebaliopsidae Hessler, 1984
Nebaliidae Samoulle, 1819
Paranebaliidae Walker-Smith and Poore, 2001
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 | Sci-Tech Dictionary. McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Leptostraca". Read more |
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