Finite element modeling of arachnid slit sensilla: II. Actuallyriform organs and the face deformations of the individual slits

摘要

Arachnid slit sensilla respond to minute strainsin the exoskeleton. After having applied Finite Element (FE)analysis to simplified arrays of five straight slits (HMI et al.J Comp Physiol A 193:445-459, 2007) we now present acomputational study of the effects of more subtle naturalvariations in geometry, number and arrangement of slits onthe slit face deformations. Our simulations show that evenminor variations in these parameters can substantially influ-ence a slit's directional response. Using white-light inter-ferometric measurements of the surface deformations of alyriform organ, it is shown that planar FE models are capa-ble of predicting the principal characteristics of themechanical responses. The magnitudes of the measured andcalculated slit face deformations are in good agreement. Atthreshold, they measure between 1.7 and 43 nm. In a lyri-form organ and a closely positioned loose group of slits, thedetectable range of loads increases to approximately 3.5times the range of the lyriform organ alone. Stress concen-tration factors (up to ca. 29) found in the vicinity of the slitswere evaluated from the models. They are mitigated due tolocal thickening of the exocuticle and the arrangement ofthe chitinous microfibers that prevents the formation ofcracks under physiological loading conditions.