Bug-Eared: Human and Insect Ears Share Similar Structures
2012 11 22

By Marissa Fessenden | ScientificAmerican.com

In a noteworthy example of convergent evolution, Katydid ears have evolved components resembling those of humans, albeit on a much smaller scale



A rainforest katydid has ears that evolved to be remarkably like those of humans and other mammals. The insect’s hearing organ, although tucked in the crook of its front legs, has components that echo the structures of our own middle and inner ear, researchers have discovered.

In humans the outer portion of the ear gathers sound waves and funnels them toward the thin membrane of the eardrum, also called the tympanic membrane. The eardrum’s vibrations translate the pressure waves of sound to the three smallest bones in our body—the hammer, anvil and stirrup bones—which shake against a snail shell-shaped organ called the cochlea, whose curves are lined with sensory-cell hairs. The wiggling bones outside jiggle liquid inside the organ and trigger those cells, which send signals to the brain via the auditory nerve. Hair cells that respond to high frequencies are closest to the origin of wave propagation and cells that respond to low frequencies are located deeper within the cochlea.

Copiphora gorgonensis is a yellow-orange–faced katydid from Gorgona Island in Colombia. The insect’s hearing organ comprises a tympanic membrane that connects to a thin cuticle plate. Sound waves rock the tympanum and thus the cuticle plate like a seesaw. But the seesaw is lopsided, with the fulcrum closer to one end. This setup translates larger movements from air pressure waves to smaller, more powerful motions in the cuticle plate. The plate creates ripples in a fluid-filled chamber akin to an unfurled cochlea. Inside this chamber sensory cells are arranged like a keyboard from high- to low-frequency sensitivity.



The cuticle plate plays the same role as the tiny hammer, anvil and stirrup of mammalian ears, but in miniature. The katydid’s entire ear spans just 600 microns, a U.K.-based research team reports in the November 16 issue of Science. (A micron is one millionth of a meter.)

[...]

Read the full article at: scientificamerican.com






Related Articles


Latest News from our Front Page

NATO Exercise in Ukraine Coincided with MH-17 Shoot-down
2014 07 24
Rapid Trident was omitted from the flurry of coverage on the shoot-down MH-17. From the U.S. Army in Europe website: Rapid Trident supports interoperability among Ukraine, the United States, NATO and Partnership for Peace member nations. The exercise helps prepare participants to operate successfully in a joint, multinational, integrated environment with host-nation support from civil and governmental agencies. ...
Warning of ’imminent’ terror attack in Norway
2014 07 24
Norwegians were warned Thursday of the concrete possibility of a terror attack occurring in that country at the hands of people with connections to an extremist group in Syria. A press conference was called in Oslo, Norway on Thursday where an announcement was made of a "possible concrete threat" to national security in that country from terrorists related to an extremist ...
Judge says government can access everything in a Gmail account
2014 07 24
All your emails are belong to us. At least that’s what the latest court order from a judge in New York says. The warrant, granted on June 11, states that the government can access all the content and files contained in a Gmail account. Yes, this is a significant blow to privacy. The subject of this specific search relates to a money laundering ...
Scotland Yard Spied on Grieving Families: secret surveillance after police victim shot seven times in head ’by mistake’
2014 07 24
More terror from the ’anti-terror’ brigade. Undercover police gathered evidence on 18 grieving families By Rob Evans and Vikram Dodd | The Guardian Undercover police officers secretly gathered intelligence over two decades on 18 families fighting to get justice from the police, it was revealed on Thursday. The intelligence covering high-profile campaigns was collected between the mid-1980s and 2005, and affected grieving families ...
Air Algerie AH5017 with 116 onboard goes missing for hours, found crashed in Mali
2014 07 24
An Air Algerie flight carrying 110 passengers and six crew members has reportedly crashed in Mali after having disappeared from radar early on Thursday morning between Burkina Faso and Algeria. A French Ministry of Defense official told Fox News that the two French fighter jets located the wreckage of the plane, which had crashed in Mali. An airport official additionally confirmed ...
More News »