Meeting Abstract
Acceleration from slow to fast swimming in the Pteropod Mollusc Clione limacina includes two biomechanical changes in wing activities: a change in angle of attack and wing stiffening. In our search for mechanisms of the latter, we investigated three very different potential contributors to wing stiffness. Dorsoventral muscles run from the dorsal epithelium to the ventral epithelium, and are used to collapse the wing during wing retraction. Indirect evidence suggests they may also contract during the change from slow to fast swimming. During the acceleration, heart rate increases significantly. An analysis of the circulation of hemocoelic fluid indicates that blood is directed from the heart directly to the wings, then the head, and via a restricted pathway, to the body and tail. The fluid motion during fast swimming indirectly supports an increase in fluid pressure in the wings in the early stages of fast swimming. Finally, and electrophysiological investigation of slow-twitch swim muscles (which drive slow swimming, and whose activity is enhanced during fast swimming) show that 10% of the muscle fiber sustain a high-frequency firing activity that is independent of rhythmic drive from the swim pattern generator. The high-frequency activity sustains contraction of the muscle cells during both phases of the wing-beat cycle.
