Meeting Abstract
50.5 Thursday, Jan. 6 The Effects of Serotonin on Leech Muscle Mechanics GERRY, S.P.*; ELLERBY, D.J.; Wellesley College; Wellesley College sgerry@wellesley.edu
The longitudinal body wall muscle of leeches (Hirudo verbana) supplies mechanical power during three distinct behaviors: swimming, crawling and suction feeding of blood. We quantified longitudinal muscle strain during these behaviors in vivo using sonomicrometry. Swimming was characterized by sinusoidal strain patterns of ± 8.4% the mean segmental length (Lm) relative to swimming. Crawling and feeding segmental strain patterns were both similar, involving a period of constant-rate longitudinal shortening. The primary difference was a shift in the operating segmental length ranges of these movements associated with the body volume increase during feeding: crawling 108% – 46 % Lm, feeding 145% – 97 % Lm. To determine how the muscle accommodates such a wide functional repertoire, the mechanical properties of the longitudinal muscle were investigated in vitro. Serotonin has been shown to alter the passive properties of the body wall and stimulate feeding. Muscle preparations were bathed in saline or 10μM serotonin solution and subjected to strain patterns mimicking those measured in vivo with optimal stimuli for maximizing work output. Serotonin reduced passive muscle stress and increased active stress causing a shift in the active length-tension curve. Serotonin likely modulates body wall mechanical properties during feeding by allowing the muscle to function at lengths that would previously have been on the unstable descending limb of the length-tension curve.
