Wind spectra and the response of the cercal system in the cockroach

Abstract

Experiments on the cercal wind-sensing system of the American cockroach, Periplaneta americana, showed that the firing rate of the interneurons coding wind information depends on the bandwidth of random noise wind stimuli. The firing rate was shown to increase with decreases in the stimulus bandwidth, and be independent of changes in the total power of the stimulus with constant spectral composition. A detailed analysis of ethologically relevant stimulus parameters is presented. A phenomenological model of these relationships and their relevance to wind-mediated cockroach behavior is proposed.

Air motion sensing hairs of arthropods detect high frequencies at near-maximal mechanical efficiency

“…This is particularly true for signals of abiotic origin, such as wind turbulence near the ground [29], but biologically relevant signals also have strong low-frequency components [8,14]. The fact that larger angular displacements (however suboptimal) are observed at lower frequencies might reflect a compromise between obtaining the maximum possible sensitivity at higher frequencies and keeping a good sensitivity at lower frequencies.…”

“…Natural airflows are often broadband, with most energy located in the lower frequencies [6,8,14,28]. This is particularly true for signals of abiotic origin, such as wind turbulence near the ground [29], but biologically relevant signals also have strong low-frequency components [8,14].…”

“…Therefore, the sensory information from filiform hairs also goes through at least one active transduction step. What matters in the end is the efficient transmission of information to the nervous system [8,[22][23][24], which is an issue that should be further addressed in the light of our results using electrophysiological recordings.…”

“…It is also known that some arthropods such as hunting spiders use airborne signals to detect prey [3][4][5]. Despite some findings of general significance [6][7][8], the question as to which features of airborne signals are recognized by the animal to trigger and guide such behaviours clearly needs further attention.…”

“…Existing studies suggest that the power spectra of ethologically relevant and background biological airflows are dominated by relatively low frequencies [7,8,14], which therefore constitute the range of signals that are easiest to capture. By revealing an unsuspected mechanical optimization of filiform hair receptors in the frequency range higher than that of maximum angular deflection, our study points towards the existence of spectral signatures that may be weak, but have been sufficiently relevant to maintain evolutionary pressure on the hair's mechanical properties.…”