Crista acustica in insect ears modeled by an inhomogenous granular chain

International audience ; Insect ears are found on the thorax (in some Hemiptera), the abdomen (in grasshoppers, cicadas, some moths), or the front tibia (in crickets, katydids). Crista acustica -also named Siebold's organs- is the sensory organ linked to tympanum when located in forelegs. It is a collection of individually-tuned scolopidia -the most fundamental unit of mechanoreceptor organs in insects- that can discriminate frequencies. A remarkable geometrical property of the arrangement of the soma or cell body of hearing sensing cells -the inner hair cells in the cochlea of mammals and human beings and the scolopidia in the hearing organs of invertebrates- has not yet been explored. We will focus on the arrangement of the cells of the scolopidia of crista acustica in the fore tibia of certain Orthoptera (eg, grasshoppers, crickets, katydids). It consists of a collection of perfectly aligned sensory cells which forms a crest on top of a hollow tracheal tube behind the tympanum. Such a crest can interestingly be modeled as an inhomogenous granular chain linked to a substrate. We will show that the dynamical response in both time and frequency domains of this neurally tunable chain also strongly depends on its anatomical pre-arrangement.