25 July 2020
Fast ant on hot sand
Published online 17 October 2019
A desert ant’s fast locomotion reveals impressive adaptations, and may offer lessons for designing robots.
The Saharan silver ant, Cataglyphis bombycina, has puzzled biologists: it is the fastest running ant of the Cataglyphis genus, can move across yielding desert sands at extremely high temperatures, yet it has shorter legs than a sister species, Cataglyphis fortis, which lives on cooler and firmer salt pans.
“Even among desert ants, the silver ants are special, since they are adapted to the extreme sand dune habitat in the Northern Sahara,” says arthropod neurobiologist Harald Wolf of the University of Ulm in Germany.
Being able to move around fast at the hottest time of day allows the ants to scavenge for food, while most competitors and predators are inactive.
The researchers used detailed video analysis to reveal what they describe as outstanding behavioural, physiological and morphological adaptations that allow the shorter-legged C. bombycina to move so fast.
The adaptations allow the ant’s legs to move faster than those of its longer-legged relatives, spend less time in contact with the surface, and possess an almost perfect synchrony in the movement of two sets of three legs. These alternating ‘tripods’ consist of the front and rear legs on one side of the body and the middle leg on the other.
“We were really surprised to find that the ants can reach stride frequencies of up 40 Hertz, which must require muscle contraction speeds close to known physiological limits,” says Wolf. He also explains that the small time spent in contact with the surface is achieved by “flying through the air” between strides, even at comparatively low walking speeds.
In addition to the contribution to understanding insect locomotion and evolution, Wolf sees potential applications for designing walking robots or vehicles that have to deal with sandy surfaces. Perhaps robotic landers sent to other worlds will apply lessons learned from desert ants.
“The authors' painstaking investigation…provides a prime example of the power of comparative studies in functional morphology and behavioural physiology,” says neuroethologist Rüdiger Wehner of the University of Zurich, who was not involved in the study.
Zoologist Tom Weihmann at the University of Cologne, Germany, also not involved in the study, describes the research as “rock-solid experimental work”. He adds, however, “[It] also shows that there is still much research required in order to understand the underlying physical principles and control mechanisms” involved in achieving such impressively fast locomotion.
Pfeffer, S. E. et al. High-speed locomotion in the Saharan silver ant Cataglyphis bombycina. J. Ex. Biol. http://dx.doi.org/10.1242/jeb.198705 (2019).