Jumping spiders can hear you from a great distance, says a new study published in the journal Current Biology.
You know how insects are featured with incredible sensory abilities in horror movies, right? Or, how Peter Parker turns into a superhero with enhanced senses after being bitten by a (radioactive) spider?! Well, we might be having a real version of what is depicted in films: a super-hearing jumping spider! It was previously known that the latter was endowed with amazing sight. Now, a discovery made by Cornell University researchers shows that it can hear from a distance too. This challenges previous notions claiming that spiders only hear nearby sounds.
This was proved when the team endeavoured to listen to what a jumping spider was hearing by taking a look at its neural activity. A non-invasive method was concocted by one of the authors, Gil Menda, to achieve this without killing the animal. The team used metal microelectrodes to probe into its brain (leaving behind only self-sealing tiny holes in the spider) to view neurones firing. It was, thus, brought to light that the spider had auditory neurones that would detect sounds from distances up to 3 metres (the equivalent of 600 spider body lengths).
“We are the first and only lab that has successfully and fully been able to tap into what the spider’s brain is listening to,” said Ron Hoy, Cornell professor of neurobiology and behavior and the senior author of the study.
Now, how does the spider sense sounds 3 metres away? Further investigation has revealed that the spider’s sensitive long leg hairs triggers the same neurones when stimulated by distant sounds. These hairs might be sensing nanoscale air particles that get excited at sound waves. It is to be noted that previous studies have linked these hairs (and those found on other body parts of spiders) with the ability to sense air particles and vibrations occurring in the vicinity of the animal.
Testing different sound frequencies, the team has found that the jumping spider is sensitive to a range thereof: from high frequencies to very particular low ones (90Hz). Is there a reason for this obviously carefully-elaborated scheme? Since nothing in nature is the product of mere chance, with everything holding a reason of being, the scientists dug deeper, and found that 90Hz was around the same frequency at which the spider’s sworn enemy, parasitic wasps, beat their wings. The researchers exposed the spiders to these frequencies to watch their behaviour.
“When we played 90 Hz, 80 percent of the spiders froze for up to a second, before they turned and jumped,” said Menda.
Freezing is a response of surprise animals display upon hearing something. The spiders did so to evaluate the level of danger of the situation to be able to avoid wasps that might be on the look-out for movement.
Watch a video of the jumping spider here.
The jumping spider is not the only one which can hear. Menda has found yet others that can: fishing spiders, wolf spiders, netcasting spiders, and house spiders.