Surprising candidate found for title of world’s fastest land animal29/04/2014 08:55:43
The cheetah doesn't get a look in, and the previous record holder, the Australian tiger beetle, has been knocked off top spot as the world’s fastest animal by a mite no bigger than a sesame seed. The mite, Paratarsotomus macropalpisis, was recently recorded running at up to 322 body lengths per second; the beetle only attains 171 body lengths. This is the measure of speed that reflects how quickly an animal moves relative to its body size. By comparison, a cheetah running at 60 miles per hour reaches a mere 16 body lengths per second. If this measure is extrapolated to the size of a human, the mite’s speed is equivalent to a person running at roughly 1,300 miles per hour.
The California undergraduate college student, Samuel Rubin, who spent last summer setting stop watches on the remarkable mites said the discovery was exciting not only because it sets a new world record, but also for what it reveals about the physiology of movement and the physical limitations of living structures.
“It’s so cool to discover something that’s faster than anything else. Just to imagine, as a human, going that fast compared to your body length is really amazing,” said Rubin. “But beyond that, looking deeper into the physics of how they accomplish these speeds could help inspire revolutionary new designs for things like robots or biomimetic devices [using an imitation of elements of nature to solve complex human problems].”
Rubin’s advisor, Jonathan Wright, professor of biology at Pomona College in Claremont, California, became interested in the mites while studying the effect of muscle biochemistry on how quickly animals can move their legs. Both relative speed and stride frequency increase as animals get smaller, and in theory, muscle physiology should, at some point, limit how fast a leg can move.
“We were looking at the overarching question of whether there is an upper limit to the relative speed or stride frequency that can be achieved,” said Wright. “When the values for mites are compared with data from other animals they indicate that, if there is an upper limit, we haven't found it yet.”
The mite is local to Southern California and is readily found running in rocky habitat or even pavements. Although it was first identified in 1916, little is known about its habits or food sources. The research team used high-speed cameras to record the mites’ sprints in the laboratory and in their natural environment. “It was actually quite difficult to catch them, and when we were filming outside you had to follow them incredibly quickly as the camera’s field of view is only about 10cm across,” said Rubin.
The research team was also surprised to find the mites running on concrete that reached temperatures of up to 140°F (60°C). This is significantly higher than the upper lethal limit of most animals. The mites also are adept at stopping and changing directions extremely quickly, attributes the researchers are investigating further for potential insights that may be relevant to bioengineering applications.