HIGH-SPEED VIDEO CINEMATOGRAPHIC DEMONSTRATION OF STALK AND ZOOID CONTRACTION OF VORTICELLA-CONVALLARIA

Stalk contraction and zooid contraction of living Vorticella convallar ia were studied by high-speed video cinematography. Contraction was mo nitored at a speed of 9000 frames per second to study the contractile process in detail. Complete stalk contraction required approximately 9 ms. The maximal contraction velocity, 8.8 cm/s, was observed 2 ms aft er the start of contraction. We found that a twist appeared in the zoo id during contraction. As this twist unwound, the zooid began to rotat e like a right-handed screw. The subsequent stalk contraction steps, t he behavior of which was similar to that of a damped harmonic oscillat or, were analyzed by means of the equation of motion. From the beginni ng of stalk contraction, the Hookean force constant increased, and rea ched an upper limit of 2.23 x 10(-4) N/m 2-3 ms after the start of con traction. Thus, within 2 ms, the contraction signal spread to the enti re stark, allowing the stalk to generate the full force of contraction . The tension of an extended stalk was estimated to be 5.58 x 10(-8) N from the Hookean force constant of a stalk. This Value coincides with that of the isometric tension of a glycerol-treated V. convallaria, c onfirming that the contractile system of V. convallaria is well preser ved despite glycerol treatment.