Goblin-faced spiders hang on their webs, and like gymnastics, they turn upside down to catch insects flying from the air. New research has found that to hear the sound of their prey coming, the spiders “listen” to the flapping of their tiny wings using a special organ in their spindly legs.
The organ looks like an array of parallel slits cut into the spider’s outer skeleton; located near the top of each foot, each mid gauge 0.0000003 and 0.000007 inch (10-200 nanometers) length. These tiny slits contain nerve cells that detect small changes in pressure caused by sound waves traveling through the air; The organ then sends this information to the brain.
Armed like that, goblins face off spider (Deinopis spinosacan hear sounds up to 6.5 feet (2 meters) away and receive frequencies between 100 and 10,000 hertz, according to a new study published October 29 in the journal Current biology. Humans can hear sounds between 20 and 20,000 hertz, depending on the context.
“It’s very alien to us because we don’t have this sensory system,” said study author Jay Stafstrom, a postdoctoral fellow in sensory biology at Cornell University.
Of course, humans use eardrum to detect sounds, but spiders don’t have an eardrum. That said, Stafstrom and his colleagues suspect that goblins might rely on some form of hearing to capture prey flying from the air – and new research supports that doubt.
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The authors found that certain noises caused the spiders to roll; As if on a signal, the spider would hear a sound and make a sudden half-turn as if it were rushing towards a passing bug. The Goblin-faced spider can be found in jungle areas of Australia, Africa and some parts of the United States, including Florida, according to Cosmos Magazine; The little spiders, which Measure under an inch (1.5-2.5 cm long), nestled among palm leaves and other vegetation and used their agile acrobatics to catch moths, mosquito and fly over.
Stafstrom told Live Science that the flip was “ballistic fast, very fast … and they were surprisingly accurate”, in terms of the spider’s ability to capture prey while in flight. “From a little spider, with a little bit brain, it’s very impressive. “
In general, love-faced spiders are known for their visuals rather than their hearing. “They have the biggest one eyes of any type of spider, “says Stafstrom. These spiders hide from predators all day, camouflage to mingle with the plants they live in. Their giant night-vision eyes detect insects crawling on the ground.To catch the terrifying cows, the spiders hang from a net near the ground and trap the bugs in one. Small, stretchable nets that hold between the fours.
The spiders deploy the same net to catch insects flying, but they bend their bodies backwards to direct the net upwards, rather than to the ground. At first, however, it was unclear whether spiders rely on their night vision to target their nets at flying prey.
In an earlier study, published in 2016 in the journal Biology Letters, Stafstrom determined whether the love-faced spider needs eyes to catch insects flying. He blindfolded the spiders using dental silicone, a opaque plastic and found that they could no longer catch prey crawling from the ground, but they were able to pluck flying insects from above. are not. Apparently, they were relying on some senses other than their eyesight, Stafstrom said.
In the new study, Stafstrom and his co-authors played different sounds for the spiders to see if one could trigger their signature flip. When exposed to low frequency sounds, between 150 Hz and 750 Hz, the spiders will purr back and stretch their nets as if to catch a bug. The authors note that these low-frequency sounds mimic the flapping patterns of different flying insects. The authors found that there are no sounds of a frequency that cause the spider to point forward toward the ground, confirming that the spider uses sight, not hearing, to catch crawling prey.
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Compared to the low frequency sounds, the high frequency sounds did not make the spiders tumble. However, electrical records of the spider’s brain cells reveal that specific groups of brain cells, or nerve cells, respond to high frequencies, namely between 1,000 Hz and 10,000 Hz; sensory organs in the spider’s legs react to the same range of sounds. The authors speculate that, since insects do not flap their wings at such a high speed, the spiders can also listen to the shrill calls of predatory birds.
“That could be an early warning sign, that a bird that could end your life may be nearby,” Stafstrom said. “We’d really like to know, ‘Are these spiders listening the bat? ” he added, but the study did not include frequencies high enough to mimic most bat calls.
While spider hearing research is still relatively new, several other species of spiders can also hear sounds, notes Stafstrom.
For example, a jumping spider senses and responds to sounds more than 9.8 feet (3 m) away, Live Science has reported before. Jumping spiders have pressure-sensitive leg feathers in response to the movement of air particles around them. The goblin face spiders also have these special hairs, and jumping spiders have the same sensation on their legs as the face goblins.
“We suspect that both spiders are using both systems,” but that has yet to be confirmed, Stafstrom said.
With the discovery that goblins use their hearing to capture prey, Stafstrom and his team now wonder how the spiders can discern the direction of a certain sound. They plan to place the spiders in an arena and play sounds from a variety of angles, to see if the spiders change their acrobatic habits to aim their nets in the respective direction.
Originally published on Live Science.