Tritocerebral segment see tritocerebrum

tritocerebrum n. [Gr. tritos, third; L. cerebrum, brain] (AR-THRO) The posterior (third) small part of an arthropod brain that gives rise to nerves that innervate the labium, the digestive tract (stomatogastric nerves), the chelicerae of chelicerates, and the second antennae of crustaceans. see metacerebrum.

tritonymph n. [Gr. tritos, third; nymphe, young woman] (AR-THRO: Chelicerata) In Acari, the third stage nymph.

tritosternum n. [Gr. tritos, third; sternon, chest] (ARTHRO: Chelicerata) In Mesostigmata, a secondary, ventral, bristlelike sensory organ just behind the gnathosoma.

triturate v.t. [L. tritum, rub to pieces] To rub or grind to a fine powder; masticate; pulverize.

triungulin, triungulinid n. [L. tres, three; ungula, claw] (ARTHRO: Insecta) First-instar larva of some hypermetamor-phic Neuroptera, Coleoptera, Hymenoptera, and the Strep-siptera (triungulinid), which are active, compodeiform oligopods. see planidium.

trivial name An obsolete designation by Linnaeus for the specific name; vernacular name.

trivium n. [L. trivium, crossroads] (ECHINOD: Asteroidea) Collectively, the three rays of a sea star farthest from the madreporite. see bivium.

trivoltine n. [L. tres, three; It. volta, time] (ARTHRO: Insecta) Having three annual broods, especially in the silkworms of Bombycidae.

trixenic a. [Gr. treis, three; xenos, guest] The rearing of one or more individuals of one species in association with three known species of organisms. see axenic, dixenic, mon-oxenic, polyxenic, synxenic, xenic.

troch n. [Gr. trochos, wheel] A band of cilia found on troco-phores and related larvae.

trochal disc (ROTIF) Anterior ciliated disc functioning in locomotion and/or food ingestion.

trochalopodous a. [Gr. trochos, wheel; pous, foot] (ARTHRO: Insecta) Refers to a posterior coxae having an articulation of a ball and socket joint. see pagiopodous.

trochantellus n. [Gr. dim. trochanter, runner] (ARTHRO: Insecta) In Hymenoptera, the proximal end of the femur; sometimes appearing as a second segment of the tro-chanter.

trochanter n. [Gr. trochanter, runner] (ARTHRO) A segment or segments of an insect or acarine leg that articulate basally with the coxa and distally with the femur; a pivot or rocking joint; the first cheliceral segment.

trochanteral organ (ARTHRO: Insecta) In Collembola, a group of short setae on the trochanter.

trochantin n. [Gr. trochanter, runner] (ARTHRO: Insecta) Any small intercalated sclerite of an insect appendage. a. The basal segment of the trochanter when two-jointed. b. A small sclerite in the thoracic wall, just anterior to the base of the coxa.

trochiform a. [Gr. trochos, wheel; forma, shape] 1. Shaped like a top. 2. (MOLL: Gastropoda) In Trochidae, a flat-sided conical shell, without a highly acute spire and rather flat at the base.

trochlea n. [Gr. trochilia, pulley] A pulley-like structure, short, circular, compressed and contracted in the middle of the circumference.

trocholophous a. [Gr. trochos, wheel; lophos, crest] (BRACHIO) A lophophore with a simple disk around the mouth, bearing usually a single row of unpaired filamentary appendages, rarely a double row of paired appendages.

trochophore n. [Gr. trochos, wheel; phora, bearing] An invertebrate free-swimming larva found in many groups, marine turbellarians, nemerteans, brachiopods, phoronids, bryozoans, mollusks, sipunculids, and annelids, commonly pear-shaped and provided with a prominent equatorial band of cilia and sometimes one or two accessory ciliary circlets.

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