Research published in a prestigious journal studying the mechanics of lizards' locomotion - Clark Now

Research published in a prestigious journal studying the mechanics of lizards’ locomotion – Clark Now

Professor Philip Bergman’s laboratory at Clark studies functional evolutionary morphology.

How did the lizard cross the road? It depends.

In a new study published in the prestigious Proceedings of the National Academy of Sciences, Philip Bergmann, a professor of biology, has researched how a lizard’s movement relates to its body shape—full-limb and short-bodied, limbless and long-bodied, or somewhere in between. in “Coordination of small limbs and long bodies: the geometric mechanics of swimming terrestrial lizardsBergmann and his co-authors, Daniel Goldman, Baxi Zhong, Eva Erickson, and Tian Yu Wang from Georgia Techconducted interdisciplinary research to study how the evolutionary process affects the movement of lizards.

“Snakes evolved from lizards, so their ancestors had four limbs and a short body,” explains Bergman. “At some point, it is believed that they became burrowed – and in the process, they lengthened their bodies and lost limbs. This is one of the main hypotheses behind how snakes evolved.”

To study body-limb coordination in diverse lizards, Bergmann and colleagues used biological experiments, engineering theory for locomotion, and even a lizard robot.

Bregman says there are major differences in the way each animal moves. Full-limbed lizards use a side-to-side motion or “standing wave” of their body, while their limbs push them forward. Limitless lizards and snakes use their stomachs to propel themselves, and movement along their bodies moves from front to back, in what is known as a “travel wave”.

However, Bergmann adds, there are “intermediate” types that have elongated bodies and hardly any limbs. These are the animals that he and his colleagues have studied in order to understand how they move.

“What we found is that when you go from a lizard-like or four-legged body shape to a snake-like body shape, you get a transition in how the body curves … where they put more of their weight on the body. It’s a situation where the body and limbs share the weight of the animal.” They move more and more to that traveling wave that the snake uses. The involvement of the abdomen, the thrust from the body or from the abdomen’s contact with the ground, means that the traveling wave enhances their movement and allows them to move more quickly.” Researchers refer to this movement as “floor swimming.”

Geometric mechanics, a type of mathematical modeling, was used to predict how the animals would move based on their shape – predictions then tested with a lizard robot. Mathematical modeling matched the robot’s movements and confirmed what they observed among real animals in nature. The moving, snake-like wave motion was the ideal way of forward motion when the body was in contact with the ground.

“As the evolutionary biologist on the team, it’s exciting to be able to support these evolutionary stories with solid data,” Bergman says.

Additionally, the research has potential applications in robotics, given what they’ve discovered about the most effective means of locomotion on various surfaces.

Finding a common language between the fields of biology and physics in the study was among the most challenging aspects of the project, Bergman says. The work of monitoring rare species was completed years ago in remote parts of Australia or the Philippines.

The Proceedings of the National Academy of Sciences (PNAS), a peer-reviewed journal of the National Academy of Sciences (NAS), is one of the world’s most multidisciplinary science journals. Having their papers accepted into the journal is a remarkable achievement. “It publishes research across all sciences, not just biology, so it’s very selective in terms of who gets published there, or the importance of the research that includes,” Bergman says. “It’s a very high bar.”

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