U research traces geckos’ evolution

The research could have biological and industrial applications.

by Rebecca Harrington

New University of Minnesota research released last week produced a comprehensive family tree that can be used for future research on geckos — and adhesives.

Researchers used DNA sequence data to trace the evolutionary history of geckos and found geckos have evolved their sticky toes 11 different times. The findings, published in the journal PLoS ONE, were the product of a joint effort from the University, Villanova University and the University of Calgary.

Tony Gamble, a postdoctoral researcher at the University and co-author of the study, said they found that in an environment with boulders, for example, geckos evolved sticky toepads. But in sandy environments, sticky toepads would be inconvenient, so geckos evolved to not have them, he said.

The family tree can show bioengineers the environments and time periods in which geckos evolved their sticky toes so they can understand how to design adhesives for different environments.

Gamble said researchers and bioengineers can use the findings to design adhesives, surgical tape or even a Spider-Man suit.

“That saves us, or people that are interested in bioengineering, a lot of effort in redesigning the wheel,” Gamble said.

He said the research also helped to reclassify geckos, because people historically classified geckos by their toes, but their research shows that isn’t the best way to do it because geckos can gain and lose this characteristic over evolutionary time.

“Hopefully, this family tree helps straighten out just how we think about geckos and classify them,” Gamble said, “as well as forming this really nice framework for asking evolutionary biology questions.”

At the molecular level, geckos use van der Waals forces — atomic attractions — to stick to surfaces, aided by the shape of their feet and microscopic hair-like outgrowths.

Bioengineering adhesives

Gamble said understanding how the shape of geckos’ toes allows them to cling to things can be useful for bioengineers to design 3-D objects.

Kelly Anderson, laboratory manager of 3M’s adhesives research lab, said the company is aware of research developments but that it’s much harder to design commercial products based on biology.

“There is definitely some intriguing work that shows … advantages you can get through some of these mimics of [a] gecko kind of material,” she said, “and there’s various approaches that are being looked at.”

But the way geckos stick to things is old news in the adhesives industry, said John Miller, technical director of 3M’s Industrial Adhesives and Tapes Division lab.

“Van der Waals interactions are pretty much the standard mechanism for why adhesives stick in the first place,” he said. “Certainly, geckos and their feet don’t have a corner on that particular market.”

Miller also said 3M would be interested in how it could bioengineer adhesives based on gecko research.

Future research

Using the family tree from the research, Gamble said he’s now studying how sex characteristics evolved in geckos. Geckos can determine the sex of their offspring by sex chromosomes, like humans and birds, or by incubation temperature.

Just like they did with sticky toes, Gamble said he’ll plot sex characteristics on the family tree to find when and where they evolved over time.

“Geckos are ideal in that they’ve got pretty much every sex-determining mechanism that occurs in vertebrates,” he said. “This is just a perfect model for us to understand how these mechanisms transition.”

Although geckos aren’t currently a model organism for research on sex characteristics in the biological world, Gamble said he would “of course” like it to be.

Until then, he said, geckos are at least a model for sticky-toed robots and Spider-Man suits.