Jumping frogs hard landings

Frogs belly flopping and face planting is not just funny to watch. It is interesting science with major implications. Just ask the world of biology. Right now, the buzz is all about these belly flopping and face planting frogs.

Talk escalated when Dr. Rick Essner, from SIUE’s College of Arts and Sciences Department of Biological Sciences, submitted an article for review and publication. Naturwissenschaften, a German multidisciplinary journal, accepted and published the study. The study began as an examination of landing abilities of basal frogs, according to Essner. However, his interest stemmed from work as a master’s student at Southeast Missouri State University and as a postdoc at the University of Pennsylvania.

There, Essner’s interest grew towards an obscure group of frogs in the family Leiopelmatidae. These “primitive” frogs are still found in the Pacific Northwest (Tailed Frogs) and New Zealand (New Zealand Frogs).

“The evolutionary split between “primitive” and “modern” frogs occurred over 200 million years ago prior to the breakup of the giant supercontinent Pangaea,” Essner stated. Following this breakup, the Tailed Frog lineage was carried northward into North America while the New Zealand Frogs became isolated as New Zealand broke away from Australia.

Despite the great passage of time, “Tailed Frogs and New Zealand frogs held on to a number of ancestral anatomical features that were lost by other frogs. These include extra vertebrae, free ribs, a ‘tail-wagging’ muscle and a cartilaginous pad in the pelvic girdle,” Essner continued.

Given this primitive anatomy, Essner wondered if the behavior of leiopelmatid frogs might be equally primitive. “Previous researchers noted that these frogs share unusual swimming behavior, moving their legs asynchronously, in a crawling-type gait, rather than flexing and extending their legs in unison like other frogs,” Essner observed. However, no one had previously studied their jumping behavior. Essner thought comparing the jumping behavior of leiopelmatid frogs with more advanced frogs might provide insight into the evolution of jumping.

Essner and his graduate student, Dan Suffian, traveled to the Pacific Northwest to collect Tailed Frogs and brought them back to his lab at SIUE.  Like most biologists interested in frog locomotion,  Essner’s focus began with the launch phase of jumping.  However, as they began to film the frogs jumping with high-speed video, they soon realized that it was the unusual landing behavior of Tailed Frogs that set them apart. Other frogs are known to land on their forelimbs using them as a pivot to bring their flexed hind limbs into position beneath the body so that they are ready to jump again immediately.

In contrast, the Tailed Frogs kept their legs extended throughout the jump and never landed on their forelimbs, resulting in a belly flop or face plant landing. Essner contacted Dr. Phil Bishop, a researcher from the University of Otago in New Zealand, and verified that the New Zealand frogs exhibited similar landing behavior. Based on this evidence, they concluded that frogs evolved jumping in a stepwise manner, with controlled landings appearing after the split between “primitive” and “modern” frogs.

This observation gave Essner the direction he needed to push outside the box. “[His] work is one of those forehead slapping, gee-whiz! why didn’t I think of that? moments,” according to Dr. Paul Brunkow, department chair and associate professor at SIUE. Essner’s observations and study will become part of textbooks soon, he added. It has great potential to add to base knowledge. Landing in smaller animals is not as important as they have less inertia when they fall. But when larger animals fly, landing safely and efficiently becomes much more important, he concluded.

Essner plans continuing work on this issue. He and several researchers from Ohio University and the University of Otago, New Zealand are continuing their collaboration in order to push farther. The researchers will work to fill gaps between the “primitive” and “modern” frogs. The hope is to show how the evolution of frogs progressed. “The goal is to provide additional evidence that [evolution] occurs in a step-like pattern,” said Essner. “Each step in the evolution of complex locomotion builds on prior steps,” he concluded.

There are also undergraduate students working with Essner in his lab at SIUE. With guidance from Essner, the students work will explore differences among frogs in their aquatic landing behavior. “The frogs keep us busy during experiments, as they are prone to not cooperating with us,” Biology major Andrew Bulla stated. “It’s always interesting working in Dr. Essner’s lab, whether it’s doing experimental design, data collection, or analysis. It’s exciting to be able to work on a project that may lead to a better understanding of anuran evolution,” he concluded in reference to his experience with Essner.

(All videos and photos courtesy of Rick Essner.)

Filed Under: Biological Sciences • Scholarly Activities