The spider facing the ogre, named for its huge eyes, hides during the day, hunts at night, hangs down from Florida palm leaves, and casts silk nets on insects on the ground and in the sky. Researchers report in the magazine that in addition to their incredible night vision effects, these spiders can also hear their predators and prey. Current biology October 29, 2020. Spiders have no ears. They have hair and joint receptors on their legs, which can pick up sounds from a distance of at least 2 meters. The results showed that spiders can hear low-frequency sounds made by insect predators and high-frequency sounds made by bird predators.
Ron Hoy, professor of neurobiology and behavior at Cornell University, said: “I think many spiders can actually hear, but everyone thinks that spiders’ sticky webs can catch prey, so they are only good at Detect vibration at close range.” University. “Vibration detection can detect vibrations on the web or the ground, but it is our job to detect airborne interference at a distance. This is our job. Spiders do this, but they use specialized receptors instead of eardrums. .”
This high-speed video shows the backward attack of the ogre spider. Image source: Sam Whitehead
Instead of passively waiting for the prey to fall into the web and get stuck, the spider facing the ogre uses the web as a weapon. After being completely still during the day and fusing with the surrounding palm leaves, they appear at night, hung near the ground, and cast a net on careless insects like a net. When they use keen night vision devices to catch prey on the ground, they can also catch insects in the sky by striking backwards carefully, which does not seem to rely on vision.
“In previous studies, I actually put dental silicone on their eyes, so they couldn’t see it,” said lead author Jay Stafstrom, a postdoctoral fellow in Hoy’s lab. “And I found that when I put them back in nature, they can’t catch prey from the ground, but they can still catch insects from the air. Therefore, I’m pretty sure these spiders are using different sensing systems to hunt the flying insects. insect.”
Although this research suggests that spiders may be audible, the research suggests that they can do it. By observing spiders’ responses to different tones and measuring their neural responses by placing electrodes in the spider’s brain and legs, the research team determined that spiders can hear sounds up to 10 kHz, much higher than walking sounds or flying insects .
Stafstrom said: “When I play low audio frequencies, even at a distance, they will strike like insects, but they don’t work at higher frequencies.” “The truth is that we know we are not close and cause They vibrate, so we can do this from a distance. This is the key to knowing that they can really hear.”
Hearing these higher frequencies may not help hunting, but it can help them stay alert while avoiding their predators.
“If you give an animal a threatening stimulus, we all know the fight or flight response. There are also invertebrates, but the other “f” is “freeze.” These spiders do just that.” Hoy said. “They are in a mysterious state. Their nervous system is asleep. But once they take any obvious stimulus, namely prosperity, the neuromuscular system is activated. This is a selective attention system.”
Although these results clearly indicate that spiders can detect sounds very well, the researchers are next interested in testing directional hearing-whether they can tell where the sounds come from. If they can still listen in a targeted manner, this may help explain their acrobatic hunting style further.
Hoy said: “What I find really surprising is that to cast a net on the fly, they have to do a half backflip and spread the net at the same time, so they are actually playing midfield.” Any animal is vital, but I think this spider will really bring some interesting surprises.”
Reference: Jay A. Stafstrom, Gil Menda, Eyal I. Nitzany, Eileen A. Hebets, and Ronald R. Hoy, “The Ogre, Web Spider Uses Auditory Clues to Detect Prey in the Air”, October 29, 2020, Current biology.
DOI: 10.1016 / j.cub.2020.09.048
This work was supported by the National Science Foundation