Chemoceptor see chemoreceptor

chemodifferentiation n. [Gr. chemeia, pert. chemistry; L. differens, dissimilar] The chemical change in cells preceding their visible characteristic difference in embryonic development.

chemoheterotroph n. [Gr. chemeia, pert. chemistry; heteros, different; trophe, nourishment] An organism that uses organic compounds as both energy and a carbon source.

chemokinesis n. [Gr. chemeia, pert. chemistry; kinesis, movement] Increased movement of an organism due to the presence of a chemical substance. chemokinetic a.

chemoreceptor n. [Gr. chemeia, pert. chemistry; L. receptor] A sense organ stimulated by chemical substances that may be perceived as smell (olfaction) or direct contact.

chemoreflex n. [Gr. chemeia, pert. chemistry; L. reflexus, bent or turned back] A reflex as a result of chemical stimulus.

chemosensory a. [Gr. chemeia, pert. chemistry; L. sensus, sense] Being sensitive to chemical stimuli. see chemore-ceptor.

chemosynthesis n. [Gr. chemeia, pert. chemistry; synthesis, composition] 1. Synthesis of organic chemical compounds in organisms. 2. A type of autotrophic nutrition through which organisms obtain their energy by oxidation of various inorganic compounds instead of from light. see photosynthesis.

chemotaxis n.; pl. -taxes [Gr. chemeia, pert. chemistry; taxis, arrangement] Movement of a motile organism or cell in response to chemical stimulus. a. Positive chemotaxis: movement toward the stimulus; chemotropism. b. Negative chemotaxis: movement from the stimulus. see taxis, tro-pism.

chemotropism n. [Gr. chemo, pert. chemistry; trope, turn] Reaction induced by a chemical stimulus. see tropism.

chevron n. [Gr. chevron, rafter] (ANN: Polychaeta) A V-shaped black, chitinous jaw piece at the base of the eversible pharynx of some Glyceridae.

chevron groove (MOLL: Bivalvia) A V-shaped furrow on the cardinal area for ligament insertion.

chiasma n.; pl. -mata [Gr. chiasma, cross] 1. (ARTHRO: In-secta) A crossing of nerves in the nerve center. a. External (outer): a crossover between the lamina ganglionaris and the medulla externa. b. Internal (inner): a crossover between medula externa and medula internal. 2. An X-shaped chromosome formation seen in meiotic cell division, due to breakage, exchange, and reciprocal fusion of equivalent segments of homologous chromatids. chiasmic a.

chiasmatype theory A Genetic theory postulating chiasmata are the result of crossing-over; being formed at the right points at which the exchange between (non-sister) chromatids took place.

chiaster n. [Gr. x; aster, star] (PORIF) A type of microsclere aster with very blunt rays.

chiastoneury n. [Gr. chiasma, cross; neuron, nerve] (MOLL) In prosobranchs and a few other taxa, a condition in which the visceral loop is distinctively twisted; crossing of the visceral connectives; streptoneury. chiastoneural a. see orthneury, euthyneury.

chilaria n.pl.; sing. chilarium [Gr. cheilos, lip] (ARTHRO: Che-licerata) In Merostomata, small rudimentary appendages on the reduced 7th (pregenital) metamere of king crabs.

chilidium n. [Gr. dim. cheilos, lip] (BRACHIO) A plate covering the notothyrium, when present, in the dorsal valve; chilidial plates if more than one. see homeochilidium.

chilognath n. [Gr. cheilos, lip; gnathos, jaw] (ARTHRO: Diplo-poda) Fusion of the first maxillae into a lower lip or gnatho-chilarium.

Chilopoda, chilopods n.; n.pl. [Gr. cheilos, lip; pous, foot] A group of terrestrial arthropods, commonly called centipedes, characterized by having numerous trunk segments, each with a single pair of walking legs, except the first segment that bears a pair of forcipulate poison fangs.

chiloscleres n. [Gr. cheilos, lip; skleros, tough] (ARTHRO: In-secta) Dark brown spots, on either side of the labrum in certain ant larvae.

chimera, chimaera n.; pl. -ras [Gr. chimaira, she-goat] An individual with a mixture of tissues, genetically different in constitution. see gynandromorph.

chimney n. [Gr. kaminos, fireplace] (MOLL: Bivalvia) A tube formed of agglutinized particles derived from boring, extending over the posterior end of the shell and sometimes extends anteriorly nearly to the mesoplax. see siphonal tube.

chimopelagic a. [Gr. cheimon, winter; pelagos, sea] Certain deep-sea organisms that appear at the surface only in winter.

chink n. [A.S. cinu, chink or crack] 1. A long and narrow cleft, crack or slit. 2. (MOLL: Gastropoda) The margin of the columella in Lacuna; umbilical chink.

chironym, cheironym n. [Gr. cheir, hand; onyma, name] A manuscript name for a species; an invalid name until published.

chirotype n. [Gr. cheir, hand; typos, type] The type specimen designated in a manuscript as the "chironym" that becomes valid upon publication.

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