tube foot


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tube foot

[′tüb ‚fu̇t]
(invertebrate zoology)
One of the tentaclelike outpushings of the radial vessels of the water-vascular system in echinoderms; may be suctorial, or serve as stiltlike limbs or tentacles.
References in periodicals archive ?
The tube foot wall is opaque, white, and thrown into a series of closely spaced annular folds when retracted.
Localized bending typically occurs at the base, while the remainder of the tube foot remains essentially straight and thus pivots about the base.
An individual tube foot first elongates and bends at the base so that the tip of the foot points in the direction of motion.
An individual tube foot is first protracted downward from the ambulacrum into the sediment.
Once attached, the tube foot retracts, pulling the food toward the mouth.
clathrata were removed show that contraction of an ampulla occurs during protraction of its associated tube foot and vice versa.
Elongation of a tube foot is caused by a decrease in volume of its associated ampulla.
This is caused by contraction of the longitudinal muscle of the tube foot wall.
Bending of the tube foot involves the same musculature as that used for elongation and shortening.
Our results are in agreement with those of Smith (1946) who suggested, on the basis of both direct observation of the tube feet and ampullae and calculations of volume accommodated by the ampullae during tube foot retraction (Astropecten irregularis, Asterias rubens), that "little, if any fluid enters or leaves the tube foot ampulla system during these movements" (p.
The connective tissue fibers observed in both the tube foot and the ampullar wall play a crucial role in the mechanics of the tube foot and the ampulla.
The tube foot can be modeled as a right circular cylinder wrapped by a single turn of an inextensible helical fiber.