Contrary to the wisdom poured out by standard textbooks that spiders detect only nearby sounds, jumping spiders are actually capable of hearing sounds from a distance, a Cornell study has found. In fact, they can sense sounds from as far as 3 meters (9.8 feet).
The Cornell researchers comprised an interdisciplinary team from the fields of psychology, medicine, computational biology, biological statistics and physics.
Published online in the journal Current Biology on Oct. 13, the pioneering study describes the unique methods used in the research. These include techniques such as inserting metal microelectrodes in a jumping spider's tiny brain to gauge auditory neurons' response in picking up far-field sounds.
"The sensory world of the tiny jumping spider was thought to be dominated by sight and tactile touch," said Paul Shamble, the lead researcher.
"Surprisingly, we found that they also possess an acute sense of hearing. They can hear sounds at distances much farther away than previously thought, even though they lack ears with the eardrums typical of most animals with long-distance hearing," added Shamble, who conducted the work in Ron Hoy's lab at Cornell University.
Success Of Interdisciplinary Research
Shamble is a leading specialist in spiders and a distinguished fellow at Harvard University. Co-researcher Gil Menda is a postdoctoral researcher who developed a new technique for documenting the neural activity of the jumping spider.
Taking the help of Binghamton University professor of mechanical energy Ron Miles, the researchers ran a few experiments under a special cage that eliminated vibrations. Using high-speed video, they were able to record how the spiders changed in their behavior when exposed to sound pulses.
Further research showed how the jumping spiders' hearing ability is sensitive to certain frequencies, particularly to the wing beats of enemies like parasitoid wasps.
The jumping spider also displayed freezing behavior, a startled response to special sounds, the team noted.
"When we played 90 Hz, 80 percent of the spiders froze" for up to a second before turning and jumping, said Menda.
Menda has also found evidence of unique hearing powers in four other spider species: wolf spiders, net-casting spiders, house spiders and fishing spiders.
The current study expands on the early studies on hearing in spiders started by Charles Walcott, professor emeritus of neurobiology and behavior at Cornell. In 1959, Walcott discovered that house spiders can detect audio stimuli from a sensory organ located in their legs, called a lyriform.
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