Australasian Science: Australia's authority on science since 1938

Trap-jaw Spiders Strike like Lightning

Mecysmaucheniidae spiders, which live only in New Zealand and southern South America, are drab and tiny spiders that hunt for prey on the ground. However, a study published in Current Biology (http://tinyurl.com/hyg9ulv) has found that these spiders have a remarkable ability to strike their prey with lightning speed.

Lead author Hannah Wood of the Smithsonian Institution’s National Museum of Natural History says that the Mecysmaucheniid family of spiders sit with their jaw-like chelicerae open and ready to snap when insect prey come close enough to strike. “The high-speed predatory attacks of these spiders were previously unknown,” she says. “Many of the species I have been working with are also unknown to the scientific community.”

While this kind of predatory behaviour had been seen before in some ants, Wood says it was unknown in arachnids. Furthermore, Wood’s team estimated that this high-speed, power-amplified strike has evolved at least four different times within Mecysmaucheniids.

High-speed videos of 14 species revealed a great range of cheliceral closing speeds. The fastest species snaps its chelicerae more than two orders of magnitude faster than the slowest species.

In fact, the power output from four of the spider species exceeded the known power output of their muscles. Therefore, Wood explains, the spiders’ movements can’t be directly powered by their tiny muscles, particularly given the short times and small distances covered during a strike. This means other structural mechanisms must allow the spiders to store the energy required to produce such powerful movements.

The researchers have already described some anatomical differences in the power-amplified trap-jaw spiders, but Wood says they aren’t quite sure how it works and are now conducting further investigations to find out.

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 says.