apterygogenea n.pl. [Gr. an, without; pteryx, wing; genos, race] (ARTHRO: Insecta) Insects that are wingless in all stages and assumed to be descended from wingless ancestors. see ptergogenea.
Apterygota, apterygote n. [Gr. an, without; pterygion, wing] A subclass of primitively wingless insects containing the bristletails, silverfish and rock jumpers. see Pterygota.
apyrase n. [Gr. an, without; pyr, fire; -ase, enzyme] An enzyme that functions in the utilization of energy.
apyrene a. [Gr. an, without; pyren, kernel] (MOLL) Designates nonfunctional sperm with no flagella or chromatin. see eu-pyrene, oligopyrene.
aquamarine n. [L. aqua marina, sea water] Blue, blue-green or green in color.
aquatic a. [L. aqua, water] Pertaining to living or growing in water.
aqueous a. [L. aqua, water] Of or of the nature of water; watery.
aqueous humor The fluid in the anterior chamber of the eye. see vitreous humor aquiferous a. [L. aqua, water; ferre, to bear] (MOLL) Supplying water or watery fluid, as the aquiferous canals.
arachnactis n. [Gr. arachne, spider; aktis, ray] (CNID: Antho-zoa) The larval stage of anemone-like cerianthids.
Arachnida, arachnid n. [Gr. arachne, spider] A class of the phylum Arthropoda that includes the scorpions, mites, spiders, harvestmen and ticks, etc.
arachnidism n. [Gr. arachne, spider; ismos, denoting condition] (ARTHRO: Chelicerata) Envenomation by an arachnid, such as a spider, tick or scorpion. see arachnism.
arachnidium n. [Gr. arachne, spider] (ARTHRO: Chelicerata) The spinning apparatus of spiders, consisting of the spinning glands and their ducts and the spinnerets. arachnid-ial a.
arachnism n. [Gr. arachne, spider; ismos, denoting condition] (ARTHRO: Chelicerata) Poisoning, or poisoned condition due to envenomation by a spider. see arachnidism.
arachnoid, arachnoideal a. [Gr. arachne, spider; eidos, form] (ARTHRO: Chelicerata) 1. Resembling a member of the Arachnida. 2. Resembling a spider's web, thin and fine, filmy.
arachnologist n. [Gr. arachne, spider; logos, discourse] One who studies the arachnids.
aragonite n. [fr. Aragon, in Spain] 1. A calcium carbonate, dimorphous with calcite. 2. The innermost layer of a shell. 3. (CNID: Anthozoa) The skeleton of coral, produced by the calicoblastic epithelium.
arakoderan a. [Gr. arake, bowl; deros, skin] (NEMATA: Se-cernentea) Pertaining to a caudal ala that completely surrounds the cloacal area. see leptoderan; peloderan.
araneiform a. [L. aranea, spider; forma, form] Spiderlike in appearance.
araneology n. [L. aranea, spider; Gr. logos, discourse] That branch of zoology that treats only of spiders.
arboreal a. [L. arbor, tree] Pertaining to or living in or among trees.
arborescent a. [L. arbor, tree] Tree-like in character or appearance; branching like a tree, as some species of mol-lusks and corals.
arborizations n.pl. [L. arbor, tree] A tree-like branching of terminal fibers of axons or collaterals.
arbovirus n. Any of a group of (ar)thropod-(bo)rne (virus)es, including the causative agents of yellow fever, viral encephalitis and certain febrile infections, that are transmitted to man by various mosquitoes and ticks.
arc n. [L. arcus, bow] Any object having a bowlike curvature.
arcade n. [L. arcus, arch] (NEMATA: Secernentea) Lateral col lecting tubules of the excretory system of Ascaris.
arcade cells (nemata) The nine anteriormost cells that are believed to form the lips, two opposite each esophageal lumen radius and one opposite each sector.
archaeocytes n.pl. [Gr. arche, beginning; kytos, container] 1. (PORIF) Large, wandering amoebocytes with multiple phagosomes in the mesenchyme; nurse cells; trophocytes. 2. A totipotent amoeboid cell.
archaestomatous a. [Gr. arche, beginning; stoma, mouth] (ANN) Describing a group, Archaeostomata of former classifications, with a mouth derived directly from the blas-topore of the embryo.
archebiosis n. [Gr. arche, beginning; biosis, manner of life] Abiogenesis.
archecentric a. [Gr. arche, beginning; kentron, center] Designating or pertaining to an original type. see apocentric.
archedictyon n. [Gr. arche, beginning; diktyon, net] (ARTHRO: Insecta) The irregular network of cuticular ridges on the wings of many fossils.
archegenesis n. [Gr. arche, beginning; genesis, beginning] Abiogenesis.
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