Procuticle
The procuticle is the major portion of the exoskeleton of an insect (and various other arthropods); its exact composition and structure may differ somewhat among different taxa, but certain aspects can be generalized:
* When first secreted by the epidermis, it is soft, pliable, and pale, as much of the chemical composition is chitin.
* The chitin molecules are intertwined to form microfibrils, and the microfibrils are often laid down in parallel to form layers ("lamina").
* The microfibrils are embedded in a protein matrix, and it is the chemical process of cross-linking between these protein chains (called sclerotization) that causes hardening and darkening of the outer portion of the procuticle; this sclerotized layer is called the exocuticle to differentiate it from the unsclerotized portion below it, or endocuticle.
* When sclerotization is complete, the regions of exocuticle form rigid sclerites, and are separated by membranous areas of endocuticle which retain their flexibility.
* The exocuticle cannot be digested during the molting cycle (see ecdysis), but the endocuticle can be resorbed, so only the exocuticle and epicuticle are shed.
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procuticle — n. [L. pro, before; cutis, skin] (ARTHROPODA) The thicker layer beneath the epicuticle consisting of endocuticle and exocuticle that lends mass and strength to the cuticle; it contains chitin, sclerotin and also calcium carbonate and calcium… … Dictionary of invertebrate zoology
procuticle — noun The major portion of the exoskeleton of an insect or arthropod … Wiktionary
procuticle — pro·cu·ti·cle (pro kuґtĭ kəl) [pro + cuticle] the layer of the exoskeleton of certain crustaceans and arthropods beneath the epicuticle, which contains chitin as the principal constituent; it is composed of an endocuticle and an… … Medical dictionary
procuticle — pro·cuticle … English syllables
procuticle — (ˈ)prō+ noun Etymology: pro (I) + cuticle : the chitinized part of the cuticle of an insect … Useful english dictionary
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Epicuticle — The epicuticle is the outermost portion of the exoskeleton of an insect (and various other arthropods); its exact composition and structure may differ somewhat among different taxa, but certain aspects can be generalized: * It is secreted by the… … Wikipedia
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crustacean — /kru stay sheuhn/, n. 1. any chiefly aquatic arthropod of the class Crustacea, typically having the body covered with a hard shell or crust, including the lobsters, shrimps, crabs, barnacles, and wood lice. adj. 2. belonging or pertaining to the… … Universalium