Meeting Abstract
Temperature has a profound effect on the contractile properties of muscles. Bats must maintain high locomotor performance in challenging thermal conditions, with convective heat loss across the flapping wings and radiative heat loss to the night sky. Presumably, critical wing muscles operate at relatively low temperatures but maintain adequate performance for flight. Distal wing muscles like the extensor carpi radialis longus (ECRL) in Carollia perspicillata, a small tropical fruit bat, may operate in vivo at 10-15°C below rectal temperature. Previously, we evaluated the isometric and isotonic contractile properties of the ECRL in C. perspicillata at 22, 27, 32, and 37°C, finding low Q10s relative to other vertebrates, including mammals. Here, we perform isolated muscle preparations of a mouse muscle of similar size to the ECRL, the extensor digitorum longus (EDL) at the range of temperatures used previously and additionally at 40 and 42°C. We predict that Q10s for rate-related processes in the mouse EDL will be higher than in the ECRL across the measured temperature range. Peak values of Vmax and the fastest twitch and relaxation times were observed at 37°C in the bat ECRL and at 40 and 42°C in the mouse EDL. Both muscles declined in performance above those temperatures. Q10s for each temperature interval are similar in the two muscles relative to each muscle’s maximum temperature. This indicates that the ECRL has a lower temperature optimum (as opposed to a broader range of maximal performance) relative to the mouse EDL. This may indicate adaptation in the intrinsic properties of C. perspicillata wing muscles to habitually low temperatures in the wing.
