It's not just a matter of panic and chance. Springtails, one of nature's most extreme self-launchers, turn out to be much more acrobatic than scientists thought.
Springtails, poppy seed-sized insect cousins, "are famous because they know how to jump but also famous because they have no control at all," says biomechanist Victor M. Ortega- Jiménez of the University of Maine in Orono.
He and colleagues used high-speed video to challenge that received no-control "wisdom" in a study published on November 7 in Proceedings of the National Academy of Sciences.
Most people ignore springtails because they are difficult to see with the naked eye. Furthermore, the 3,000 or so known species cause little or no harm to humans and thus do not receive the attention that ticks and fleas do. Some springtails resemble lemon drop candies, with large eye spots and six legs, while others grow more stretched out (SN: 42420).
Springtails are no longer considered insects because of their unusual jumping organs. Springtails (in the Collembola taxonomic group) evolved as insect-like animals with no wings but a long, hinged ground smacker called a furcula that latched underneath the springtail body.
Releasing it to whack against the ground or even water propels a springtail high into the air and away from danger, such as a hungry fish. Some springtail species have ground-smacked themselves to safety at 280 times their body length per second. That's the kind of jump that biologists used to think would send a small body flying upward with no control.
Ortega- Jiménez recalls that questioning that notion begins with pandemic musing. He was at Georgia Tech in Atlanta, but the labs were closed and he was spending "a lot of time with my family on rivers in Georgia," he says. That's how he saw springtails jumping out of the water but landing on land — and the jumps didn't look random to him.
When the labs reopened, he and a large group of colleagues tackled the issue of what exactly happens during springtails' emergency launches. Focusing on the semi-aquatic species Isotomurus retardants, films at speeds of up to 10,000 frames per second demonstrated impressive control.
Springtails aren't just helpless squiggles flailing through the air. Both video and mathematical models showed that they curl their bodies in flight in such a way that they stop tumbling and fall oriented for landing. This orienting while falling is something that cats and some other animals do well, but springtails do it faster than any other animal testing, in less than 20 milliseconds.
Long thought to leap randomly into the air when danger approaches, tiny springtails (Isotomurus retardants) have been discovered to have some control over their leaping direction. They also curve their bodies to prevent tumbling in the air and use a tubelike structure on their underside to help them land upright 85 percent of the time. (For viewing purposes, high-speed video has been slowed.)
Another distinguishing springtail body part is a collophore, a short wide tubelike organ that sticks out of the abdomen. The animal in profile appears to be a plastic toy fresh from the mold, with the collophore hanging from its tummy like a tab that hasn't been snapped off yet.
A small amount of water in the tubular collophore provides weight, which prevents the jumper from bouncing into somersaults as it splashes down on the water's surface.
The team discovered that springtails in lab pools landed on their feet about 85 percent of the time. Mimicking the landings with a springtail-inspired robot no bigger than a penny resulted in a 75% landing success rate.
All of this attention to springtail jumping prowess pleases Anton Potapov, a soil animal ecologist at the Germany's University of Göttingen who was not involved in the study. He describes springtails as "not only cute and interesting to look at; they are also among the most numerous and functionally important animals on our planet."
"You can find them almost anywhere, and they contribute to so many ecosystem processes," including plant and microbial growth. May they jump far and high.
V.M. Ortega-Jiménez and colleagues Semiaquatic springtails perform directional take-off, aerial righting, and adhesion landing. doi:10.1073/pnas.2211283119. Proceedings of the National Academy of Sciences, Vol. 119, November 7, 2022.