New York: Jumping spiders can perceive airborne sound despite not having ears or ear drums, finds a new study.
The family of jumping spiders includes about 5,800 species – 13 per cent of all spider species – that live around the world.
In general, the family is known to perceive the world through sharp eyesight and ability to sense vibrations (such as a struggling fly in a web) instead of hearing. It was previously thought jumping spiders were deaf to airborne sounds.
In the experiment, the researchers implanted electrodes in sound-sensing areas of a spider’s brain and placed the animal in a metal box.
Scientists then played sounds at the same frequency as the buzz in various locations around the box. Consistently, spiders froze in response to the threat – a behaviour observed in the wild – and electrodes recorded spikes in brain activity as spiders ‘listened’ for the predator.
“The experimental setup presented the spider with only airborne sound rather than vibrations through the ground. Spiders are known to be incredibly good at detecting very subtle motion of the surface they are on,” said Ronald Miles, professor at the Binghamton University, US.
“We had to make sure that the vibrations were too small to influence the results and the anechoic chamber, one of the quietest places on Earth, was the perfect place to test that. We demonstrated this using measurements in our chamber and also provided an analytical model of the vibration of the fixture that the spider was placed on when it reacted to sound,” Miles added.
Spiders had neural responses to sounds between 80-380 Hertz at 65 decibels (normal restaurant conversation) from close distances to 10 feet or more.