refractive a. [L. re, back; frangere, break] To turn from a direct course; turned aside.
refractory n. [L. re, back; frangere, break] 1. Not readily in-fectible; not amenable to therapy. 2. Unresponsive; the intermission after excitation during which repetition of the stimulus fails to induce a response in nerves.
refringent a. [L. re, back; frangere, to break] Refractive; to deflect rays of light.
refugium n.; pl. -ia [L. re, back; fugere, flee] An area that has escaped the great changes of the region as a whole, as un-
glaciated mountain tops in an ice age.
regeneration n. [L. regenerare, to regenerate] The replacement of a part or parts lost through mutilation or otherwise.
regenerative budding (BRYO: Gymnolaemata) Budding inside a broken zooid.
regenerative cells (ARTHRO: Insecta) Cells of the stomach (ventriculus) that may be singly, in pairs beneath the columnar cells or grouped into clusters (nidi) or arranged in crypt-like outpocketings; functioning in renewal of other epithelial cells when destroyed by secretion or degeneration during molting or pupation.
regression n. [L. re, back; gradi, to step] 1. Regressive evolution. 2. A statistical method of comparing paired observations.
regressive character A character being reduced or lost in the course of phylogeny.
regressive evolution The appearance of characters in a taxon that are usually considered primitive.
regressive molting (ARTHRO: Insecta) In Isoptera, reversal during metamorphosis, when they are already in the process of developing into a particular caste, back to a less differentiated stage.
regularization (ANN) Anatomical adjustments involved in reducing the asymmetry due to unilateral splitting of mesoblastic somites.
regular triact (PORIF) A megasclere spicule with three equal rays separated by angles of 120 degrees.
regulator gene A gene that controls the action of other genes through curtailing the rate of synthesis of the products of other distant genes.
reinfection n. [L. re, again; inficere, to make] A second infection by the same microorganism after recovery from or during the course of a primary infection.
relic n. [L. reliquia, remnant] A present nonfunctional structure that was originally useful; an isolated remnant of a once widespread population.
remiform a. [L. remus, oar; forma, shape] Oar-like in shape.
remigium n. [L. remigare, to row] (ARTHRO: Insecta) The wing area anterior to the claval furrow, in both fore and hind wings; if claval furrow is indistinct, may be described as forward of the posterior cubitis. remigial a.
remigrant foramen (BRACHIO) The pedicle opening moving dorsally after an initial movement toward the ventral beak.
remiped a. [L. remus, oar; pes, foot] Having oar-shaped feet; adapted for rowing.
remotion n. [L. re, again; motus, move] (ARTHRO: Insecta) In leg movements, the corresponding movement of the coxa.
renal a. [L. renis, kidneys] Pertaining to a kidney.
renal appendage (MOLL: Cephalopoda) A sacculate organ functioning in providing blood pressure to carry blood through the gills.
renal cells Nephrocytes.
renal sac (MOLL: Cephalopoda) One of four organs of the nephridium that receives pericardial filtrate via the renop-ericardial canal and secretions from the large renal appendages.
renette a. [L. dim. ren, kidney] (NEMATA) The ventral excretory gland cell(s).
reniform a. [L. dim. ren, kidney; forma, shape] Kidney-shaped.
reniform spot (ARTHRO: Insecta) In Noctuidae, a kidney-shaped spot at the end of the discal cell.
renopericardial canal (MOLL: Cephalopoda) Ciliated canal connecting the metanephridium with the pericardial cavity.
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