Fig 1.
(a) An actual image of the bush-cricket Mimetica sp.; (b) The pinna covering the tympanal membranes of Mimetica sp., located at the femoro-tibial joint, obtained from 3D-volume renders of synchrotron micro-CT scans; (c) The hearing organ (crista acustica) located on the dorsal wall tapering in width, obtained from 3D-volume renders of synchrotron micro-CT scans; (d) A zoomed-in image of the crista acustica components, obtained from 3D-volume renders of synchrotron micro-CT scans; (e) A drawing of the human and katydid middle and inner ears for comparison.
Fig 2.
The image of the Mimetica sp. inner ear geometry forming the solution domain of the mathematical model, as obtained by synchrotron-based μ − CT scans and 3D-reconstruction.
Table 1.
The Young’s modulus and thickness of components used in the mathematical model.
Fig 3.
Tonotopy in the Mimetica sp. inner ear.
The displacement magnitude along the crista acustica at (a) 20 kHz, (b) 40 kHz, and (c) 80 kHz. The displacement magnitude along the dorsal wall at (d) 20 kHz, (e) 40 kHz, and (f) 80 kHz.
Fig 4.
(a) The transect along which the displacement magnitudes were obtained. The displacement magnitude of the dorsal wall along the transect from (a), at (b) 20 kHz, (c) 30 kHz, (d) 50 kHz, (e) 70 kHz, and (f) 80 kHz. The displacement magnitude of the crista acustica along the transect from (a), at (g) 20 kHz, (h) 30 kHz, (i) 50 kHz, (j) 70 kHz, and (k) 80 kHz.
Fig 5.
The displacement magnitude of the dorsal wall at (a) 20 kHz, (b) 40 kHz, and (c) 80 kHz, after the removal of the crista acustica.
Fig 6.
The solitary crista acustica influence on tonotopy.
The displacement magnitude of the crista acustica at (a) 20 kHz, (b) 40 kHz, and (c) 80 kHz.
Fig 7.
Mechanical network of a segment of the hearing organ.
Abbreviations are as follows: P, pressure from the travelling wave; MDW, mass of dorsal wall; KDW, stiffness of dorsal wall; KCA, stiffness of crista acustica components; MTM, mass of tectorial membrane; KTM, stiffness of tectorial membrane. The source of displacements in the inner ear are shown in red. Vibrations of the dorsal wall are transmitted to the tectorial membrane via the crista acustica components dendrites and cap cells (red arrow).
Fig 8.
The time course of the dorsal wall vibrations at (a) 20 kHz, (b) 40 kHz, and (c) 80 kHz. (d) The transect used to measure the phase response between the points P1 and P2. (e) The phase response as the travelling wave moved along the transect in (d) in the frequency range 10–80 kHz.