This Spider Has No Ears, But Still Can Hear
By admin - November 5, 2020

Orcs-like spiders, the Deinopids, got this name because of their massive eyes. They hide during the day, and at night, they run from Florida palm trees and catch their prey quite conveniently both on the ground and in the air. Aside from the fact that they can see amazingly well at night, according to a statement published in the journal Current Biology on October 29, they can also understand the voice of both the victim and the predator. Because they have no ears, spiders use balance and body receptors on their bodies to pick up sounds. In this way they perceive sounds of different frequencies even from a distance of 2 meters. Most importantly, they can understand both low and high frequency sounds, making them successful hunters and hard-to-name prey.

“Scientists believe that because spiders have a sticky web, they can only sense near-vibrations to catch prey, and I think they also have the ability to hear,” said Ron Hoy, author of the study and a professor of neurobiology and biochemistry at Cornell University. “Vibrations are perceived only as a result of direct contact with the ground, or with the net. But the perception of sound waves in the air indicates their ability to hear, but, unlike us, they perceive sound not by ears but by special receptors,” Hoy said.

Instead of just sitting around waiting for a prey to fall into their trap, spiders use their web as a weapon to attack insects. After spending the whole day in the palm leaves in a dormant state, these spiders come out at night, run down and target their nests with insects that may not even realize that they may be in danger from where they least expect it. Deinopids use night-vision to catch their prey on the ground, while in the air they perform choreographically quite interesting movements and thus attack flying insects. They do this not with the help of sight, but with the help of hearing.

“In previous studies, dental silicone was placed on the eyes of these spiders so that they could not see anything. It turned out that when I returned them to nature, the deinopids could no longer hunt on the ground, although they were just as successful in the air. To catch, “said study co-author Jay Staffstrom, a researcher at Hoy Labs.

In addition to the fact that spiders have the ability to hear, this study also indicates how well you understand them. By observing the reaction of spiders to sounds of different frequencies and by studying their response neuronal activity through electrodes located in their brains and legs, the team determined that deinopids can perceive sounds at frequencies up to 10 kHz, much higher than those of mice.

“When I turned on low frequency sounds, even from a certain distance, they became active as if they were preparing to hunt for an insect, but the high frequencies did not have the same reaction. The fact that we can transmit sounds to them from a distance is very important. “From what distance they could perceive the vibrations, it clearly indicates the ability of the spiders to hear.”

Perceiving high-frequency sounds may not help them hunt, but instead, they allow them to be more vigilant and more cautious with predators.

“We have already studied the reaction of animals when they feel threatened: fight or run away. In such cases, the reaction is characteristic of invertebrates, but in their case this reaction is manifested in fire. Deinopids are no exception. During the day their nervous system is asleep. “They ‘understand’ sounds, their nervous system is activated. It ‘s a selective system that responds differently to sounds of different frequencies,” says Hoy.