Natures wonders: ogre-based spiders use sound to catch prey (Introduction)

by David Turell , Thursday, October 29, 2020, 20:21 (1276 days ago) @ David Turell

Another weird way spiders catch a meal:

https://www.sciencenews.org/article/ogre-faced-spider-hearing-catch-insects-prey-air-so...

"Hanging upside down, the spider weaves a rectangular web between its legs. When an insect flies behind the dangling arachnid, the spider swings backward, casting the web toward the prey. This behind-the-back hunting technique is one clue that the spiders can hear an unexpectedly wide range of sounds, researchers report online October 29 in Current Biology.

“'A couple years ago, we didn’t really have a great idea that spiders could hear,” says Jay Stafstrom, a sensory ecologist at Cornell University. But now, he and his colleagues have looked at several spider species, and most can hear using specialized organs on their legs, he says. That includes jumping spiders, which respond to low frequencies. Surprisingly, ogre-faced spiders can also hear fairly high frequencies, Stafstrom says.

"Stafstrom and colleagues inserted microelectrodes into the brains of 13 ogre-faced spiders, and then played tones of varying frequencies from a speaker while monitoring the spiders’ auditory nerve cell activity. Spikes of activity revealed that the spiders can sense airborne sounds between 100 and 10,000 hertz, though not at every frequency, the team found. (Humans generally hear between 20 Hz and 20,000 Hz.)

"Nerve cells in amputated spider legs — where the slit sensilla, the organ that responds to sound vibrations, is located — also responded to the wide range of frequencies. This finding confirms that the spiders hear with their legs, the researchers say.

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“'They can obviously catch things out of the air just using sound,” Stafstrom says. And because the spiders strike only at low frequencies, they’re probably using the lower end of their hearing to listen for prey and hunt. As for the upper frequency range, “they don’t seem to be using it in a foraging context,” he says."

Comment: One wonders how the spiders learned this system since it is so complex, blindly throwing the net from sounds. The spider must have 3-D hearing as we do, but alone does not tell us how it developed naturally. Designed?