Meeting Abstract

28.4  Friday, Jan. 4  Electromyography of bat wing membrane muscles CHENEY, JA*; MIDDLETON, KM; KONOW, N; GIBLIN, EL; BREUER, KS; SWARTZ, SM; Brown University, Providence, RI; University of Missouri, Columbia; Brown University, Providence, RI; Brown University, Providence, RI; Brown University, Providence, RI; Brown University, Providence, RI Jorn_Cheney@Brown.edu

Bat wing membranes consist of a double layer of skin, and this architecture makes them thin, lightweight, and compliant. A number of small muscles, the plagiopatagiales, are embedded in the membrane, oriented approximately along the chord of the wing. These muscles both originate from and insert into this membrane. It has been hypothesized that the plagiopatagiales function to tense the membrane, which would reduce wing compliance and decrease wing camber. For this hypothesis to be correct, the plagiopatagiales must be active during flight. Further, we predict that if these muscles function to reduce wing camber by increasing membrane tension, their activity should occur during downstroke, when the membrane is cambered due to significant load. This activity pattern should only hold during steady flight. However, when a flight behavior must maximize lift, such as during landing, we expect that the muscle activity and intensity would change in order to maximize wing camber. To determine when these muscles are active during flight, if at all, we used fine-wire electromyography. We implanted sew-through electrodes in a single plagiopatagialis muscle in four individuals of the Jamaican fruit bat (Artibeus jamaicensis). Using a lightweight cable, we recorded electromyograms from the muscle during both steady flight and landing maneuvers in a wind tunnel. Consistent with our hypotheses, we found that, during steady flight, the plagiopatagiales were active during the downstroke, and during landing events, the periodic pattern of activity and recruitment changed. Overall, our results are consistent with the idea that the plagiopatagiales modulate wing camber during flight.