torose a. [L. torus, elevation] A swelling into knobs; cylindrical and swollen at intervals; torous.
torpid a. [L. torpidus, to be numb] Dormant; inactive. see aestivation, hibernation.
torqueate a. [L. torquatus, with a necklace] Having a ring or collar.
torsion n. [L. torquere, to twist] 1. Spiral bending; twisting. 2. (MOLL: Gastropoda) The theory in ancestral gastropods that a 180-degree counterclockwise twisting occurred that caused the crossing of the pleural-visceral connectives in the nervous system to form a figure eight. see chiasto-neury, detorsion.
tortuose a. [Gr. torquere, to twist] Twisting; winding; irregularly curved.
torulose a. [L. torulus, little bulge] Having knob-like swellings; moniliform.
torus n.; pl. tori [L. torus, swelling] 1. A blunt, rounded, ridge or protuberance. 2. (ANN: Polychaeta) Low ridges provided with rows of acicular hooks or minute setae or uncini. 3. (ARTHRO: Insecta) In Diptera, the pedicel of the antenna. 4. (PORIF) A more or less doughnut-shaped space around the organism, concerned with water circulation.
totipotent a. [L. totus, all; potens, capable] Said of isolated blastomeres capable of becoming complete embryos.
totomount n. [L. totus, all; mons, mountain] The mount of a whole organism for microscopic study.
toxa n. [Gr. toxon, bow] (PORIF) A bow-shaped diactinal micro-sclere.
toxicognath n. [Gr. toxikon, poison; gnathos, jaw] (ARTHRO: Chilopoda) The forcipulate poison fangs.
toxicology n. [Gr. toxikon, poison; logos, discourse] The science of poisons.
toxin n. [Gr. toxikon, poison] A poisonous substance in the secretions or excretions of a parasite.
toxinosis n. [Gr. toxikon, poison] A disease caused by the action of a toxin.
toxoglossate n. [Gr. toxon, bow; glossa, tongue] (MOLL: Gastropoda) Having a radula always enclosed in the radular sac; marginal teeth harpoon-shaped, filled with venom and loosely arranged in two rows.
toxoid n. [Gr. toxikon, poison; eidos, form] A toxin released from its toxic properties, but not from its antigenic properties.
trabecula n.; pl. -lae [L. trabecula, little beam] 1. A small bar, rod, bundle of fibers, or septum together with other trabe-culae which form part of the framework of various organs. see internuncial process. 2. (MOLL: Cephalopoda) In squid and cuttlefish, a support from the edge of the arm inward for the protection of membranes of the arm.
trabeculate a. [L. trabecula, small beam] (ANN: Oligochaeta) Used to describe seminal vesicles that develop as connective tissue proliferations from a septum that have numerous irregular spaces that remain minute until spermatogo-nia begin to enter. trabeculated a.
trachea n.; pl. tracheae [L. trachia, windpipe] 1. The windpipe. 2. (ARTHRO: Chelicerata) For Arachnida, see tube trachae, sieve trachea. 3. (ARTHRO: Insecta) The larger tubes of the respiratory system, lined with taenidia, opening to the outside through the spiracles and terminating internally in the tracheoles. 4. (MOLL: Gastropoda) see ctenidia. 5. (ONYCHO) In Peripatus, short tubes without spiral thickenings, neither branching nor anastomosing, opening externally through numerous minute spiracles. tracheate a.
tracheal gills (ARTHRO: Insecta) In aquatic larvae and some aquatic pupae, filiform, lamellate structures supplied with trachae and tracheoles, usually borne on the abdomen. see spiracular gills, blood gills.
tracheal system (arthro) A system of cuticle-line tube opening to the outside through spiracles, functioning in respiration.
tracheoblast n. [L. trachia, windpipe; Gr. blastos, bud] (AR-THRO: Insecta) Cells derived from the epidermal cells lining the trachea, that give rise to the tracheoles.
tracheoles n. [L. dim. trachia, windpipe] (ARTHRO: Insecta) The fine intracelluar terminal branches of the respiratory tubes. tracheolar a.
trachychromatic a. [Gr. trachys, rough; chroma, color] Strongly staining.
tract n. [L. tractus, region] 1. An area, region or parts of a system, as a bundle of nerve fibers between parts of the central nervous system. 2. (PORIF) A fascicular column of spicules.
Tragardh's organ (ARTHRO: Chelicerata) In Acari, a long, conical hyaline protuberance of the articulation between the body of a chelicera, and its movable jaw; oncophysis.
tragus n. [Gr. tragos, goat] (ARTHRO: Insecta) In Diptera, a somewhat elaborate lobe on the rim of the pinna of a lati-corn trumpet of some culicid pupae.
transad n. [L. trans-, across; Gr. ad, makes collective nouns] Closely related organisms separated by an environmental barrier.
transcoxa n. [L. trans-, across; coxa, hip] (ARTHRO: Chelicer-ata) A term used instead of coxa in some groups.
transcurrent a. [L. trans-, across; currens, running] 1. Extending transversely. 2. (MOLL: Gastropoda) Passing continuously around whorls crossing growth lines.
transect n. [L. trans-, across; secare, to cut] A cross section or profile of an area for study, as with organisms and/or vegetation.
transection n. [L. trans-, across; secare, to cut] Cut across or transversely; a transverse section.
transformation zone In males, that part of the testis follicle in which the spermatids develop into spermatozoa; known as spermiogenesis. see maturation zone.
transient a. [L. trans-, across; ire, to go] A passing phenomenon; of short duration.
transient polymorphism Polymorphism existing in a breeding population during the period when an allele is being replaced by a superior one. see balanced polymorphism.
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