The discovery of a previously unidentified hearing organ in the South American bushcrickets' ear could pave the way for technological advancements in bio-inspired acoustic sensors research, including medical imaging and hearing aid development.
Researchers from the University of Bristol and University of Lincoln discovered the missing piece of the jigsaw in the understanding of the process of energy transformation in the 'unconventional' ears of the bushcrickets (or katydids).
Bushcrickets have four tympana (or ear drums) -- two on each foreleg; but until now it has been unknown how the various organs connect in order for the insect to hear. As the tympana (a membrane which vibrates in reaction to sound) does not directly connect with the mechanoreceptors (sensory receptors), it was a mystery how sound was transmitted from air to the mechano-sensory cells.
Sponsored by the Human Frontiers Science Program (HFSP), the research was developed in the lab of Professor Daniel Robert, a Royal Society Fellow at the University of Bristol. Dr Fernando Montealegre-Z, who is now at the University of Lincoln's School of Life Sciences, discovered a newly identified organ while carrying out research into how the bushcricket tubing system in the ear transports sound. The research focussed on the bushcricket Copiphora gorgonensis, a neotropical species from the National Park Gorgona in Colombia, an island in the Pacific. Results suggest that the bushcricket ear operates in a manner analogous to that of mammals. Dr. Montealegre-Z said: "We discovered a novel structure that constitutes the key element in hearing in these insects, which had not been considered in previous work. The organ is a fluid-filled vesicle, which we have named the 'Auditory Vesicle'. This hearing organ mediates the process of conversion of acoustic energy (sound waves) to mechanical, hydraulic and electrochemical energy. The integration laser Doppler vibrometry and micro-CT scanning allowed us to identify the auditory vesicle and to conclude that the process relies on a tympanal lever system analogous to the mammalian ossicles. This serves to transmit air-borne vibrations to the fluid (the auditory vesicle), and also on the mechanoreceptors. Therefore the bushcricket ear performs the crucial stage of air to liquid impedance conversion and amplification just as in a mammal's ear."