Australian tiger beetle ousted as world's fastest runner

Californian researchers have recorded a new world record for the fastest running land animal - one which is no bigger than a sesame seed in size.

The Southern California mite Paratarsotomus macropalpis was 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. Extrapolated to the size of a human, this is equivalent to a person running almost 2100 km/h.

The previous record holder, the Australian tiger beetle, tops out at 171 body lengths per second. A cheetah can meanwhile attain only about 16 body lengths per second.

Professor Jonathan Wright, from Pomona College, 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; in theory, muscle physiology should at some point limit how fast a leg can move.

The research team used high-speed cameras to record the mites’ sprints in the laboratory and in their natural environment - typically rocks or footpaths. When his students documented their natural running speeds, the team realised they had found a new world record.

“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 Professor 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 research team was also surprised to find the mites running on concrete up to 60°C, a temperature significantly higher than the upper lethal temperature 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.

“Looking deeper into the physics of how [the mites] accomplish these speeds could help inspire revolutionary new designs for things like robots or biomimetic devices,” said student Samuel Rubin, who led much of the fieldwork to document the mites’ movements.

Rubin presented the findings during the Experimental Biology 2014 meeting on 27 April and at the American Physiological Society Undergraduate Research Poster Session on 28 April.

Source