nuclear whorls (MOLL: Gastropoda) The whorls of the proto-conch that emerges from the egg.
nucleate a. [L. nucleus, kernel] Having a nucleus.
nucleic acids Polymers of nucleotides that are active in inheritance as genes, plasmids, etc.
nuclei of Semper (ARTHRO: Insecta) The nuceli of the crystalline cone cells.
nucleolar chromosome Any chromosome with a nucleolar organizer.
nucleolar organizer Chromosome region that is active in nucleolus formation.
nucleolinus n. [L. dim. nucleus, kernel] A small granule within the nucleolus.
nucleolonema n. [L. dim. nucleus, kernel; Gr. nema, thread] Filamentous structures within the nucleolus of all cells.
nucleolus n. [L. dim. nucleus, kernel] Small, dense, more or less spherical bodies in the nucleus of cells associated with the nucleolar organizer.
nucleoplasm n. [L. dim. nucleus, kernel; Gr. plasma, formed or molded] The protoplasmic fluid contained in the nucleus.
nucleoplasmic index The ratio of nuclear volume to cytoplasmic volume; seems to trigger cell division; nucleoplasmic ratio.
nucleoprotein n. [L. dim. nucleus, kernel; Gr. proteios, primary] A compound of nucleic acid and protein.
nucleoside n. [L. dim. nucleus, kernel] Compounds derived by hydrolysis of nucleic acids or nucleotides consisting of a purine or pyrimidine base linked to ribose or deoxyribose.
nucleotide n. [L. dim. nucleus, kernel] Unit of the DNA and RNA molecules, including phosphoric acid, a purine or pyrimidine base, and a ribose.
nucleus n.; pl. -lei [L. nucleus, kernel] 1. A spheroidal structure present in a cell containing the chromatin. 2. (MOLL: Gastropoda) The earliest-formed part of the shell, or oper-culum, of a protoconch.
nudibranchiate a. [L. nudus, naked; branchiae, gills] (BRACHIO) Having the gills uncovered and not protected by a shell or membrane in the brachial chamber.
nudum n. [L. nudus, naked] (ARTHRO: Insecta) A small bare, sensitive portion of a butterfly antenna.
nulliplex a. [L. nollus, none; plectare, to weave] A polyploid having all genes for a particular recessive character.
numerical phenetics The hypothesis that relationship between organisms can be determined by a calculation of an overall, unweighted similarity value.
numerical taxonomy Numerical evaluation of similarity between taxonomic units and grouping of these units into higher taxa on the basis of their affinities; taxometrics. see taxonomy.
nuptial flight (ARTHRO: Insecta) In Hymenoptera, the mating flight of winged males and females.
nurse cells 1. Cells of developing oocytes that provide material for further growth; trophocytes. 2. (ARTHRO: Insecta) In some species, the nurse cells synthesize nucleic acids and possibly protein and supply them to the oocyte via inter-cytoplasmic connections. 3. (nemata) A specialized plant response to feeding sessile forms, characterized by special feeding cells around the nemas' head that are not subject to necrosis; giant cells. 4. (porif) The archaeocytes.
nutant a. [L. nutare, to nod] Nodding; drooping; having a tip bent horizontally.
nutricial castration, castration nutriciale (ARTHRO: Insecta) In Hymenoptera, the condition of undeveloped gonads in young adult females due to devoting itself to nursing larval forms instead of herself taking on the nutrition necessary for the reproductive form. see alimentary castration.
nutricism n. [L. nutrix, nurse] A symbiotic relationship in which one partner obtains all the benefits.
nutrition n. [L. nutrire, to feed] The ingestion, digestion and assimilation of food substances that includes their distribution within the organism, as well as the metabolism and elimination of waste products.
nyctipelagic a. [Gr. nyktos, night; pelagos, sea] Coming to the water surface only at night.
nymph n. [Gr. nymphe, bride] 1. (ARTHRO: Chelicerata) The immature stage of Acari and Ixodoidea with a full complement of legs; an instar. 2. (ARTHRO: Insecta) An immature stage that does not have a pupal stage. 3. (MOLL: Bivalvia) see nympha.
nympha n.; pl. -phae [Gr. nymphe, bride] 1. (ARTHRO: Chelicerata) In Acari, sclerites beneath the epigynium. 2. (MOLL: Bivalvia) The immersed area behind the beak that strengthens the margin to which the ligament is attached, or reinforcement for the normal hinge structure; ligament fulcrum; sometimes nymph.
nymphal phase (ARTHRO: Chelicerata) The second or third phase of postembryonic development; in Acari with six stases, the third phase comprised of proto-, deuto- and trito-nymphs.
nymphipara a. [Gr. nymphe, bride; L. parere, to beget] (ARTHRO: Insecta) Bearing live young in an advanced stage of development. see pupipara.
nymphochrysalis n. [Gr. nymphe, bride; chrysallis, gold colored pupa] (ARTHRO: Chelicerata) In chigger mites, a non-feeding, prenymph; a calyptostasic protonymph.
nymphoid a. [Gr. nymphe, bride; eidos, form] (ARTHRO: Chelicerata) Nymphal phase instars that cannot be homologized with nymphal instars of other species.
nymphoid reproductive (ARTHRO: Insecta) A neoteinic reproductive with wing buds; a second-form reproductive; secondary reproductive; a brachypterous neoteinic.
nymphosis n. [Gr. nymphe, bride] The process of transforming into a nymph or a pupa.
obconical a. [L. ob, inverse; conic, cone] Inversely conical; in the form of a reversed cone.
obcordate a. [L. ob, inverse; cor, heart] Inversely heart-shaped.
obese a. [L. obesus, fat] Distended; enlarged; corpulent.
obimbricate a. [L. ob, inverse; imbrex, tile] Having regularly overlapping scales. see obsite.
objective synonym One of two or more names based on the same type.
oblanceolate a. [L. ob, inverse; lanceolatus, spear-like] Inversely lanceolate oblate a. [L. oblatus, spread out] Flattened; pertaining to a spheroid of which the diameter is shortened at two opposite ends; flattened at the poles.
obligate a. [L. obligare, to be required] Pertaining to the inability to live in a different environment. see facultative.
obligate parasite A parasite that cannot exist without a host during all or some portion of the life cycle. see facultative parasite.
obligate symbiont An organism that is physiologically dependent upon a symbiotic relationship with another. see facultative symbiont.
oblique a. [L. ob, inverse; liquis, awry] Slanting; deviating from the perpendicular, or a particular horizontal direction, but not perpendicular to it.
oblique muscles 1. (ECHI) Innermost muscle layer of body wall; may form oblique or nearly transverse fascicles between bands of the longitudinal muscles. 2. (SIPUN) A thin layer of diagonally placed muscle between the circular and longitudinal muscles.
oblique vein (ARTHRO: Insecta) A slanting cross wing vein.
obliterate a. [L. obliteratus, erased] Indistinct.
oblong a. [L. oblongus, rather long] Elliptical; elongated; longer than broad.
oblong plates (ARTHRO: Insecta) In aculeate Hymenoptera, the innermost or posterior pair of plates immovably fixed on each side of the bulb and stylet of the sting.
oblongum n. [L. oblongus, rather long] (ARTHRO: Insecta) In Coleoptera wings, a special oblong cell formed when M 1 is connected with M 2 by means of one or two cross veins.
obovate a. [L. ob, inverse; ovate, egg-shaped] Inversely egg-shaped with narrower end downward.
obpyriform a. [L. ob, inverse; pyrum, pear; forma, shape] Inversely pear-shaped.
obscure a. [L. obscurus, covered] 1. Dark; dark of color; dim. 2. Remote; hidden. 3. Not well defined.
obsite a. [L. obsitus, barred] Refers to a surface covered with equal scales or other objects. see obimbricate.
obsolescence n. [L. obsoletus, to wear out] 1. The process of gradual reduction or disappearance of a taxon. 2. A gradual cessation of a physiological process.
obsolete a. [L. obsoletus, to wear out] Obscure; not distinct; atrophied; imperfectly developed.
obtect, obtected a. [L. obtectus, covered over] Covered; enclosed within a hard covering.
obtect pupa (ARTHRO: Insecta) A pupa in which the appendages are glued down to the body by a secretion produced at the larval/pupal molt. see exarate pupa.
obturaculum n. [L. dim. obturare, to plug or close] (ARTHRO: Insecta) In Anoplura, a connective-like tissue structure that divides the hemocoel of the head from the thoracic hemo-coel; continuous posteriorly with a heavy coat surrounding the thoracic ganglia; neck-plug.
obturator n. [L. obturare, to plug or close] Any structure that closes off a cavity.
obtuse a. [L. obtusus, blunt] Blunt or rounded at the extremity; not pointed. see acute.
obtusilingues n.pl. [L. obtusus, blunt; lingua, tongue] (AR-
THRO: Insecta) In a former classification, those bees with short tongues having an obtuse or bifid tip. see acutilin-gues.
obumbrate a. [L. obumbrare, to over-shadow] Overhanging, or partially concealing.
obverse a. [L. obvertere, to face] 1. Looking head on. 2. Having the base narrower than apex. 3. Being a counterpart.
obverse side of colony (BRYO) The frontal side of the colony.
obvolvent a. [L. obvolvere, to wrap around] Bending downward and inward.
occasional species A species sometimes found in a particular area, but not habitually.
occipital a. [L. occiput, back of the head] Pertaining to the occiput or the back part of the head.
occipital arch (ARTHRO: Insecta) The area of the cranium between the occipital and postoccipital sutures.
occipital carina (ARTHRO: Insecta) In Ichneumonidae Hymen-optera, a subcircular carina on the hind aspect of the head, between the vertex and hind margin of the compound eyes and the foramen magnum.
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