acrydian a. [Gr. akridion, locust, grasshopper] (ARTHRO: In-secta) Pertaining to grasshoppers or grasshopper-like.
actin n. [Gr. actus, move] A muscle protein that combines with myosin to form a contractile protein complex, actomyosin; the chief constitutent of the I and Z-band myofilaments of each sarcomere.
actinal a. [Gr. aktis, ray] 1. Star-shaped; pertaining to that area of a radiate organism from which arms or tentacles radiate. 2. (CNID: Anthozoa) Oral area of sea anemones.
actine n. [Gr. aktis, ray] (PORIF) The single ray of a star-shaped spicule.
actinenchyma a. [Gr. aktis, ray; en, in; chyma, to pour] Cellular tissue resembling a star.
actinic a. [Gr. aktis, ray] Pertaining to wave lengths between those of visible violet and X-rays, having certain chemical effects.
actiniform a. [Gr. aktis, ray; forma, shape] Having a radiated form; star-shaped. actinoid a.
actinobiology n. [Gr. aktis, ray; bios, life; logos, discourse] The study of effects of radiation upon living organisms.
actinoblast n. [Gr. aktis, ray; blastos, bud] (PORIF) The rudimentary cell of a spicule.
actinochitin n. [Gr. aktis, ray; chiton, tunic] Chitin that is anisotropic or birefringent (double refracting).
actinodont a. [Gr. aktis, ray; odous, tooth] (MOLL: Bivalvia) With teeth radiating from the beak of the shell.
actinogonidial a. [Gr. aktis, ray; gonos, seed] Having genitalia arranged in a radial pattern.
actinoid, actiniform a. [Gr. aktis, ray; eidos, shape] Raylike; star-shaped; stellate.
actinology n. [Gr. aktis, ray; logos, discourse] 1. The study of radially symmetrical animals. 2. The study of the activity of radiation.
actinomere n. [Gr. aktis, ray; meros, part] A segment of a radially segmented organism.
actinopharynx n. [Gr. aktis, ray; pharynx, gullet] (CNID: An-thozoa) Gullet of the sea anemone.
actinostome n. [Gr. aktis, ray; stoma, mouth] The mouth of a radially symmetrical animal.
actinotrocha, actinotroch n. [Gr. aktis, ray; trochos, wheel] (PHORON) A free-swimming, elongate, ciliated larva of the phylum Phoronida, bearing tentacles attached to a girdle immediately posterior to the preoral lobe.
actinula n. [Gr. dim. aktis, ray] (CNID: Hydrozoa) A larval stage that looks like either a polyp or medusa, depending upon whether the mouth is turned upward or downward.
action current The flow of electric current between a region of excitation and neighboring unexcited regions.
action potential A temporary change in potential that occurs across the surface membrane of a muscle or nerve cell following stimulation.
activator n. [L. agere, to act] Any substance that renders another substance active.
active a. [L. agere, to act] Pertaining to movement; given to action; alert.
active center The site on an enzyme molecule that interacts with the substrate molecules; where activation and reaction take place.
active transport The transportation or movement of substances through differentially permeable cell membranes against a concentration or electrical gradient with the expenditure of energy.
actomyosin n. [Gr. aktis, ray; mys, muscle] Actin and myosin linkage in myofilaments that shortens when stimulated resulting in muscle contraction.
acuate a. [L. dim. acus, needle] Sharpened; needle-shaped; sharp pointed.
aculea n.; pl. -eae [L. dim. acus, needle] (ARTHRO: Insecta) 1. In Diptera, one of the minute spines comprising the to-mentum that covers the cuticula (except the wing membrane), usually dense in adults but sparse or absent in immatures. 2. In Lepidoptera, one of the minute spines on the wing membrane.
aculeate a. [L. dim. acus, needle] 1. Pertaining to being armed with a sting or short, sharp points. 2. Furnished with acu-leae.
aculeate-serrate Armed with saw-like teeth inclined toward one direction.
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