Meeting Abstract

P2.120  Saturday, Jan. 5  Behavioral Thermoregulation Not Accompanied by Locomotor Performance Acclimation in the Medicinal Leech JEONG, J.*; DARAKANANDA, K.; HITCHCOCK, A.; CONNOLLY, E.; QUIST, A.; ROBBINS, A.; ELLERBY, D.; Wellesley College dellerby@wellesley.edu

Medicinal leeches adjust their temperature preference in relation to their nutritional status: low temperatures are preferred when energy reserves are low, reducing metabolic costs, while higher temperatures are preferred after feeding to support higher metabolic rates and rapid food processing. Although energetically favorable, low temperatures may reduce locomotor performance. In many vertebrate ectotherms continued cold exposure triggers compensatory changes in muscle contractile properties and metabolic capacity that support performance recovery. However, the capacity for locomotor acclimation in invertebrates is less well understood. Medicinal leeches were acclimated to 21˚ C and their swimming and crawling speed and kinematics quantified by video analysis. This was repeated during acute exposure to 12.5˚ C, the preferred temperature for unfed leeches, and at regular intervals while being held at this temperature over the course of 6 weeks. Acute cold exposure significantly reduced performance. Mean swim velocity and swim cycle frequency were reduced by 40% and 37%, respectively. There was no detectable recovery of performance during prolonged exposure. The kinematic viscosity of water increases with decreasing temperature and at relatively low Reynolds numbers may alter swimming performance independently of any temperature effects on muscle contraction or metabolism. To separate these effects, swimming performance was quantified at 21˚ C with the kinematic viscosity of water increased to that of 12.5˚ C water by addition of methyl cellulose. The altered viscosity reduced swimming speed by 15%, indicating part of the performance change can be ascribed to viscosity effects.