epistomal ridge (ARTHRO: Insecta) The cranial inflection of the epistomal sulcus.
epistome, epistoma, epistomis, epistomum n. [Gr. epi, upon; stoma, mouth] 1. (ARTHRO: Chelicerata) See tectum, cervix. 2. (ARTHRO: Crustacea) In brachyuran Decapoda, a plate of varying shape between the labrum and bases of the antennae; sternum of antennal somite. 3. (ARTHRO: Insecta) a. In Diptera, the oral margin; that part of the face above the mouth. b. In Odonata, the clypeus. c. In certain Coleoptera, the reduced frontoclypeal region. see peristome. 4. (BRYO: Phylactolaemata) A small, movable lip-like lobe of tissue and coelom overhanging the mouth.
epitheca n. [Gr. epi, upon; theke, case] (CNID) The external layer surrounding the theca in many corals.
epithelial layer 1. Any layer of cells, one surface of which is lining a tube or cavity. 2. (BRYO) A single layer of cells of two types: secretory cells and fat storage cells.
epithelial syncytium Multinucleated epithelial cells.
epithelial tissues Surface tissues in which the cells form regular layers, containing very little intercellular material.
epitheliomuscular a. [Gr. epi, upon; thele, nipple; L. muscu-losus, fleshy] (CNID) Pertaining to epithelium with a longitudinal contractile fiber at the base; myoepithelial.
epithelium n., pl. -lums, -lia [Gr. epi, upon; thele, nipple] An epithelial tissue, covering an external or internal surface. epithelial a.
epitoke n. [Gr. epi, upon; tokos, birth] (ANN: Polychaeta) The posterior sexual portion of certain marine worms. see atoke.
epitoky n. [Gr. epi, upon; tokos, birth] (ANN: Polychaeta) Reproduction of certain dimorphic swarming worms in which structural modifications such as enlarged eyes, nonfunctional gut and modification of parapodia for swimming occur; also called hetero-forms: heteronereis, heterosyllid. see heteronereid.
epitorma n.; pl. -mae [Gr. epi, upon; tormos, socket] (AR-THRO: Insecta) In scarabaeoid larvae, a rod extending from the inner end of the laeotorma. a. Epitorma anterior, when directed toward the apex of the epipharynx. b. Epitorma posterior when directed in the opposite direction.
epizoic a. [Gr. epi, upon; zoon, animal] Pertaining to an organism living on, or attached to the body of another animal. see endozoic.
epizoicide n. [Gr. epi, upon; zoon, animal; L. caedere, to kill] An agent that destroys epizoa.
epizoon n.; pl. epizoa [Gr. epi, upon; zoon, animal] An animal parasite living upon the exterior of the body of the host; an external parasite.
epizootic a. [Gr. epi, upon; zoon, animal] An outbreak of disease in animals in which there is an unusually large number of cases; identical to an epidemic in humans.
epizootiology n. [Gr. epi, upon; zoon, animal; logos, discourse] The field concerned with the study of diseases of animals involved in an epizootic outbreak.
epizygal n. [Gr. epi, upon; zygon, yolk] (ECHINOD: Crinoidea) The distal member of a syzygial pair of brachials. see hy-pozygal. epizygial a.
epizygum n.; pl. epizyga [Gr. epi, upon; zygon, yolk] (AR-THRO: Insecta) In certain beetle larvae, an elongate plate or bar extending from the zygum toward the clithrum on the right of the epipharynx, or embodied in the tylus; may be present when clithrum is absent.
epoch n. [Gr. epoche, stop] Subdivision of a period or division in geologic time.
epomia n.; pl. -ae [Gr. epomidios, on the shoulder] (ARTHRO: Insecta) 1. The margin of the propleural furrow in which the front femur is inserted. 2. In ichneumonid Hymenop-tera, a carina on the side of the pronotum, obliquely crossing the trough in the side of the pronotum.
epupillate a. [L. ex, out of; pupilla, pupil of eye] Without a pupil or color spot; pertaining to ocellate spots.
equal weighting Treating all taxonomic characters as equally important.
equatorial plate Plane where chromosomes gather during metaphase of mitosis or meiosis.
equidistant a. [L. aequus, uniform; distantia, remoteness] Equally spaced from any two or more points.
equilateral shell (MOLL: Bivalvia) With the shell parts equal or almost equal anterior and posterior to the beak.
equilibrating a. [L. aequus, uniform; libra, balance] Balancing equally.
equimeric a. [L. aequus, uniform; Gr. meros, part] (ANN: Oli-gochaeta) Pertaining to regenerates having the same number of segments as had been amputated. equimery n.
equipedal a. [L. aequus, uniform; pes, foot] Possessing pairs of equal feet.
equipotent a. [L. aequus, uniform; potens, powerful] Differing cell parts or organs capable of performing like functions.
equivalve a. [L. aequus, uniform; valva, leaf of a folding door] (MOLL: Bivalvia) When two valves (shells) are the same shape and of equal size.
era n. [L. aera, epoch] A division of geologic time, such as Palaeozoic, etc.; divided into periods.
eradiate v. [L. ex, out of; radiatus, rayed] To shoot forth as rays of light; to radiate.
erectopatent a. [L. erectus, upright; patens, open] (ARTHRO: Insecta) Pertaining to having the fore wings erect and the hind wings partially spread during resting.
ereisma n. [Gr. ereisma, prop] (ARTHRO: Insecta) The furcula in Sminthurus which has a fanlike structure.
eremobic a. [Gr. eremos, solitary; bios, life] Living a solitary existence.
eremochaetous a. [Gr. eremos, solitary; chaite, mane] Lacking the normal arrangement of bristles.
eremology n. [Gr. eremia, desert; logos, discourse] A science concerned with the desert and its phenomena.
eremophilous a. [Gr. eremia, desert; philos, loving] Desert loving; pertaining to animals that live in deserts or arid regions.
eremosymbiont n. [Gr. eremos, solitary; syn, together; bios, life] A species living in an ant nest for protection, not taking or contributing anything.
ergastic a. [Gr. ergastikos, fit for working] Pertaining to the integration or union of parts during evolution. see meta-plasm.
ergastoplasm n. [Gr. ergaesthai, working; plasma, form or mold] 1. Granular endoplasmic reticulum. 2. A former conception of cytoplasm, the fibrillar or flocculent masses found in many gland cells and elsewhere.
ergatandromorph n. [Gr. ergates, worker; aner, man; mor-phe, form] (ARTHRO: Insecta) An abnormal ant possessing the worker characteristics, combined with qualities of the male. see ergatogynandromorph.
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