Have you ever come upon something confounding and looked at a friend and said, “Well, that’s as mysterious as a bushcricket’s aural mechanism,” only to realize you’re the only one in the room? Then you’re in for a shock, because scientists have identified the structure allowing a bushcricket, or katydid, to hear, and as with everything that we’ve discovered about animals, humans will try to mimic it to advance upon our own non-cricket-inspired hearing devices.
For the journal Science, Dr. Fernando Motealegre-Z, of the University of Lincoln’s School of Life Sciences, reported his research involving the bushcricket Copiphora gorgonensis, a neotropical insect from the National Park Gorgona in Columbia, a Pacific island.
Katydids hear using four tympana, or ear drums, located on their forelegs. Because they don’t directly connect with the sensory receptors, no one knew exactly how they were able to process sound. Using laser Doppler vibrometry and micro-CT scanning, the research team discovered a fluid-filled vesicle, which they named the “Auditory Vesicle,” that transmits the air-borne vibrations to the fluid, and then to the sensory receptors. The way mammals hear involves the eardrum collecting sound, a middle ear impedance conversion, and a cochlear frequency analyzer. Just in case those sounded like two completely different processes, know that they aren’t.
It’s a huge discovery that insects accept and transmit audio just like we do. The fact that such mechanisms can exist in miniature form is highly encouraging to scientists looking to utilize the underlying technology for human use in acoustic sensors and actuators, and possibly hearing aids and biomedical imaging systems.
The only mystery left is figuring out how these bushcrickets are so sensitive to high frequencies. The species studied here puts out moderate frequencies of around 23kHz, but some species are able to detect extreme ultrasonic signals ranging from 130-150kHz. While it doesn’t seem like these sounds have the traveling power to go far in rainforest settings, but these insects are able to communicate from great distances, and the discovery of the auditory vesicle is the first step in understanding how.
Header image via Durotriges