Meeting Abstract
The temperature dependence of muscle work has implications for whole-organism performance in behaviors involving muscle-powered movements in variable-temperature environments. Behaviors using elastic energy-storage mechanisms are thermally robust, but this relies on the ability of muscle to do the same work at any temperature. We investigated the effects of temperature on the work done by isolated plantaris muscles from Cuban tree frogs (Osteopilus septentrionalis) while also varying the load against which the muscles were contracting. Stimulating muscle contraction through the sciatic nerve, we calculated work done on a lever ergometer by simultaneously measuring the force exerted by the muscle and the displacement of the lever. Experiments were conducted at five different temperatures (9 – 25 °C) under six different loads for each muscle. Effects of temperature on muscle work depended on the load the muscle was moving. Muscle work on larger loads was more sensitive to temperature changes than muscle work done on smaller loads. For high loads, muscle work at the lowest temperature was only 25% of the work done at high temperatures. For low loads, however, muscle work saw no reduction from high to low temperatures. This pattern may be due to the temperature dependence of muscle force output, which decreases at lower temperatures. At larger loads muscle force is a more important determinant of work than is displacement. These results suggest that performance is affected by temperature when muscles move large loads, but behaviors using muscles to move relatively small loads are robust to changes in temperature. Muscles associated with elastic structures in energy-storage mechanisms may be expected to operate at lower loads and thus maintain performance in variable-temperature environments.
