Paratarsotomus macropalpis, the fastest land animal as measure by body lengths per second

Relative to its size, a Southern California mite runs faster than any other animal and thrives in temperatures that would kill most other animals – according to new research by a team led by Prof. Jonathan Wright.

Although the mite Paratarsotomus macropalpis is no bigger than a sesame seed, it was recently recorded running at up to 322 body lengths per second, a measure of speed that reflects how quickly an animal moves relative to its body size. The previous record-holder, the Australian tiger beetle, tops out at 171 body lengths per second. By comparison, a cheetah running at 60 miles per hour attains only about 16 body lengths per second.

Extrapolated to the size of a human, the mite's speed is equivalent to a person running roughly 1300 miles per hour.

The mite is local to Southern California and is often found running along rocks or sidewalks. First identified in 1916, little is known about the mite's habits or food sources.

The research team consisted of Maria Young ‘16, Samuel (Yoni) Rubin (Pitzer '15), Prof. Wright from biology, Physics Prof. Dwight Whitaker, and Harvey Mudd Biology Prof. Anna Ahn.

Rubin presented their findings at the findings during the Experimental Biology 2014 meeting on April 27 and at the American Physiological Society Undergraduate Research Poster Session on April 28. Since then, news of the discovery has rocketed around science media, with stories appearing in Science DailyScienceDiscovery and Nature World News, among others.

"It's so cool to discover something that's faster than anything else, and just to imagine, as a human, going that fast compared to your body length is really amazing," said Rubin.

Wright became interested in the mites while studying the effect of muscle biochemistry on how quickly animals can move their legs. But it wasn't until Young and Rubin documented the mites' running speeds in their natural environment that the team knew they had found a new world record.

"Both relative speed and stride frequency increase as animals get smaller," explains Wright, "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. 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 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 10 centimeters across," said Rubin.

The research team was also surprised to find the mites running on concrete up to 140 degrees Fahrenheit (60 degrees Celsius), a temperature significantly higher than the upper lethal temperature of most animals. "They're operating at temperatures that seem to preclude activities of any other animal group. We've seen them running where there were no other animals visibly active," said Wright. 

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.

The research was funded by the Howard Hughes Medical Institute Undergraduate Science Program. The Claremont Colleges' HHMI grant funds approximately 50 summer undergraduate research projects each year.

"This project is a really great example of collaborative research across the Claremont Colleges," says Wright. "We had students from two different campuses and faculty from two campuses and two different fields."