Meeting Abstract

P3.160  Monday, Jan. 6 15:30  Tokay geckos actively modulate adhesive force STEWART, WJ*; HIGHAM, TE; Univ. of California, Riverside wstewart@ucr.edu

Many geckos can effectively move on inclined surfaces by employing their adhesive system. To do this, they unfurl their digits, initiating contact with the surface and permitting attractive forces. Parallel loading is then induced using the tensile skeleton of the digits. Although the micromechanics of adhesion are well-studied, it is unclear if and how geckos can actively modulate the strength of adhesion when clinging. Here, we test the hypothesis that geckos can control the magnitude of adhesive forces with muscles in the limbs. This was achieved by linking the resistive force generated by the toe pads of Tokay geckos (mean body mass ± 1 SD = 45.0 ± 11.1 g) when pulled on a vertical surface to muscle activity within the forelimb measured with electromyography. A high-sensitivity force transducer measured the force produced by a gecko manus when pulled upwards, downwards, and horizontally on a vertical acrylic surface. A custom force generator attached at the shoulder produced repeatable pulling forces directed medially and in parallel to the acrylic surface, while a high-speed camera imaged the digits in detail. All conditions induced shear loading. We found that a single gecko manus produced high resistive forces that, on average, were over 14 times the total body weight. Force production also varied greatly between trials for each individual, ranging on average from 11.5 to 17.5 times body weight when pulled downwards on the vertical surface. Since toe pad engagement was confirmed with video, such high intra-individual variation in force production suggests Tokays may be able to modulate adhesion strength. Determining the neuromuscular control of adhesion will help us better understand the physiological basis of force modulation in geckos. Supported by NSF IOS-1147043.