The Motion-Sensing Hairs of Arthropods: Using Physics to Understand Sensory Ecology and Adaptive Evolution

Abstract

In an effort to understand the “design” principles of arthropod filiform hairs, it is desirable to explain the effects that ecology and, therefore, natural selective pressures may have had on the adaptive evolution of these medium motion sensors in terrestrial and aquatic habitats, respectively. This is a complex interdisciplinary problem involving various facets of biology, mechanics, and mathematics. Using a simplified, physically approximate theoretical analysis, the present work places on a more general foundation the understanding of the observed variations of the maximum angular deflection and maximum angular velocity, and their respective resonance frequencies, of filiform hairs as a function of the physical parameters that affect these four quantities. Calculated results obtained using the approximate analysis are compared with corresponding results from a more exact physical analysis and with previous measurements and calculations to show that all qualitative aspects of hair behavior are correctly captured by the simplified theory. The theory is then used to explain the dependence of hair motion on the physical parameters that affect it, and to explore the sensitivity of hair motion to small changes in these parameters.