Meeting Abstract
Bat wings contain muscles whose fast, coordinated contractions are integral to the flight stroke. Muscle cooling slows contractile rates, however, and flight exposes bats to substantial convective and radiative heat losses. Since bat wings are poorly thermally insulated, a temperature gradient exists from the proximal core (warm) to the distal periphery (cool). During flights at ~22°C, in Carollia perspicillata the distal extensor carpi radialis longus muscle (ECRL) operates at ~12°C below core body temperature (Tb) while the proximal pectoralis muscle operates near Tb. The ECRL is also less temperature sensitive than the pectoralis, i.e., it experiences a proportionately smaller decline in contractile rates after a given drop in temperature. This finding raises an important question: Is this high-to-low gradient in temperature sensitivity from proximal-to-distal in the bat wing a functional adaptation to the wing’s local thermal environment, or the climate in which the bats live? To address this, we measured contractile rates in the ECRL and pectoralis muscles of C. perspicillata and Eptesicus fuscus, and in the ECRL muscle of Tadarida brasiliensis at a range of experimental temperatures (22–42°C) to determine if muscle temperature sensitivity varies interspecifically. There was little difference in the thermal sensitivities of the ECRL or pectoralis muscles between species; however, the ECRL was less temperature sensitive than the pectoralis. These results suggest that the low temperature sensitivity of the ECRL muscle in bats may be due to local thermal challenges rather than as an adaptation to largescale environmental conditions.
