Tiny trap-jaw spiders nab prey with lightning speed: study

A group of tiny trap-jaw spiders called Mecysmaucheniidae does not look like much, but they actually have a remarkable ability to strike their prey with lightning speed, scientists said Thursday.

Mecysmaucheniidae spiders, which live only in New Zealand and southern South America, are tiny, cryptic, ground-dwelling spiders that rely on hunting rather than web-building to capture prey.

In a study published in the U.S. journal Current Biology, Hannah Wood of the Smithsonian Institution's National Museum of Natural History and colleagues said they used high-speed cameras to record these spiders, which have unusual, highly maneuverable jaw-like mouth parts scientifically known as chelicerae.

Wood observed that the spiders would stalk their prey with their chelicerae wide open, snapping them shut once their prey was close enough, similar to a mouse-trap.

There are currently 25 known species in the Mecysmaucheniidae family, but she was shocked to find that capturing some species' trap-jaw movement required filming at 40,000 frames per second.

That kind of predatory behavior had been seen before in some ants, but it was unknown in arachnids, the group including spiders, she said.

"This research shows how little we know about spiders and how much there is still to discover," Wood said in a statement. "The high-speed predatory attacks of these spiders were previously unknown."

In the new study, researchers were able to record 14 species of the spiders with a high-speed camera, which revealed a great range of cheliceral closing speeds.

The fastest species snaps its chelicerae shut more than 100 times faster than the slowest species, they said.

Using DNA analysis, the team found that the high-speed strikes have independently evolved at least four different times -- a phenomenon known as convergent evolution -- within the Mecysmaucheniid family.

Aside from sheer speed, the power output from four of the spider species exceeded the known power output of muscles, meaning that the spiders' movements can't be directly powered by their tiny muscles.

Instead, other structural mechanisms must have evolved that allow the spiders to store energy to produce their ballistic movements, the researchers said.

In addition to providing new insights into spiders and their evolution, the new findings may also have broader implications.

"Studying these spiders could allow humans to design robots that move in novel ways that are based on how these spiders move," Wood said. Endit