Meeting Abstract

P3.142  Sunday, Jan. 6  Don’t swim after a large meal, crawl instead. QUIST, A.*; DARAKANANDA, K.; HITCHCOCK, A.; JEONG, J.; CONNOLLY, E.; ROBBINS, A.; ELLERBY, D.; Wellesley College dellerby@wellesley.edu

Soft-bodied organisms drive locomotor movements using antagonistic muscle layers to transmit forces via hydrostatic skeletons. Unconstrained by rigid skeletal elements, this arrangement allows for a high degree of functional flexibility. Modulation of motor outputs from central pattern generators can create distinct movement patterns, e.g. crawling and swimming, using a single muscular hydrostat. Changes in hydrostat volume potentially disrupt these movements through muscle length-tension effects and suppression of motor outputs. This is particularly apparent in organisms that undergo large volume changes, such as sanguivorous leeches where body volume may increase tenfold during feeding. Immobility after feeding increases vulnerability to predation. Swimming is the fastest locomotor mode before feeding, but is disrupted by the volume increase associated with feeding due to changes in body shape and flexibility, and inhibition of the swimming motor pattern. Crawling however is relatively unimpaired. Crawling speed remained at 80% of the pre-feed level immediately after feeding, and after 1 hour there was no detectable loss of performance relative to the pre-feed level. Broad length tension relationships in the antagonistic muscle layers of the body wall allow maintenance of contractile function despite the massive volume increase. In contrast to swimming, crawling motor patterns appear not to be suppressed by activation of body wall stretch receptors after feeding. These factors, coupled with rapid volume reduction through excretion of blood plasma, allow for a remarkable maintenance of mobility despite the mechanical challenges posed by feeding.