Cephalothorax


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cephalothorax

[¦sef·ə·lə′thȯr‚aks]
(invertebrate zoology)
The body division comprising the united head and thorax of arachnids and higher crustaceans.

Cephalothorax

 

that part of the body of arthropods formed as a result of the fusion of the cephalic and thoracic segments.

The cephalothorax is characteristic of higher crustaceans and chelicerate arthropods (Arachnida, Xiphosura, and the extinct paleozoic Eurypteridae). Among the crustaceans, the cephalothorax is formed in Decapoda by the fusion of six cephalic and seven thoracic segments. In Chelicerata it consists of the six front segments of the body (which usually bear the appendages), to which a seventh (pregenital) segment is sometimes attached.

References in periodicals archive ?
The total carotenoids content in the abdomen and cephalothorax of the shrimp of treatment A(0.5) ([approximately equal to]215 mg [kg.sup.-1]) was similar to the mean of carotenoid in the abdomen of shrimp of treatment group B(1.5) ([approximately equal to]231 mg [kg.sup.-1]), and both values were significantly higher than those recorded in treatment A(1.0), A(1.5), B(0.5) and TC (Fig.
Principal Components Variables PCI PC2 PC3 PC4 PC5 PC6 Weight 0.93 -0.14 0.04 0.13 0.3 0.04 Cephalothorax width 0.89 -0.12 0.22 0.31 -0.18 -0.03 From leg 1 0.93 -0.20 -0.20 -0.16 0.003 -0.15 Front leg 2 0.93 -0.15 -0.21 -0.13 -0.12 0.14 White patch 0.62 0.66 0.31 -0.27 -0.00 0.004 % of white patch cover 0.17 0.93 -0.26 0.20 0.002 -0.01
They were sacrificed, and the pleon and cephalothorax of each female were weighed and stored as previously described for ovigerous females (Fig.
43), the presence of lateral dorsal canals of the lateral line sensory system on the dorsal plate of Psammosteus points at the general constriction of the cephalothorax. Thus, lateral fields of tesserae were much narrower in Psammosteus than in other psammosteids, in which lateral dorsal canals were situated in wide fields of tesserae.
Cephalothorax. Eyes absent, four longitudinally divided anterior structures present near the submarginal fold of the anterior cephalic section, cephalic setae present.
(Technically, spiders have only two body parts-the abdomen and a cephalothorax that comprises both head and thorax-but they are also usually not in 18-karat yellow gold, so some poetic license is definitely permissible here.) The sunny colors and compact proportions reinforce the sweet harmlessness of this small beast.
In crustaceans, cycles of growth and molting are triggered by cholesterol-derived molting hormones (ecdysteroids) released from paired endocrine glands (the Y-organs) located in the anterior cephalothorax. During much of the molting cycle, the levels of ecdysteroids in hemolymph are kept low by the action of a peptide molt-inhibiting hormone (MIH), produced in the eyestalks.
For example, spiders have only two body parts (cephalothorax and abdomen), while insects have three body parts (head, thorax and abdomen).
The body of the mite is divided into two regions; a front part called the cephalothorax and a hind part called the abdomen.
Habitus (not shown) fusiform, tapering from the posterior part of the cephalothorax to the posterior part of the body.