New Discovery of Hearing Organ in South American Bush Cricket’s Ear Spurs Microphone Research

Research aimed at developing ultrasonic microphones with insect-like sensitivity is to continue in the rainforests of Colombia and Ecuador. Following the recent discovery of a previously unidentified hearing organ in the South American bush cricket’s ear, a scientist from the University of Lincoln (UK) will now study the role of this Auditory Vesicle in hearing sensitivity. Dr Fernando Montealegre-Zapata, from the University’s School of Life Sciences, aims to understand how bush crickets, also known as katydids, pick up on ultrasonic frequencies in their natural environment. The insects communicate using the highest-pitched calls in nature (130-150 kHz), which are not detected by humans. The males produce sound by rubbing their wings to attract distant females. Dr. Montealegre-Zapata said, “This animal can detect ultrasonic signals even at long distances. The problem is that at such high frequencies the sound travels in very short wavelengths which get diffracted, meaning the sound gets weaker as more obstacles are in the dispersive path. However, the bush cricket’s small ear is still able to detect this fading ultrasonic energy at long distances. I want to test how the bush crickets manage to do that in a field environment. The fluid in the katydid “cochlea,” which I named the Auditory Vesicle, is the key element in the hearing process. We want to investigate why this is the case and the first step is testing its sensitivity in their natural environment and revealing the chemical composition.” In mammals, hearing relies on three stages: an eardrum collecting sound, a middle ear impedance converter and a cochlear frequency analyzer. Dr Montealegre-Zapata recently demonstrated that the bush cricket’s ear performs these same steps in the hearing process, something previously unknown in insects.
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