Science

This new gecko species slips out of its scales to evade threats

Strange geckos that live on Madagascar have a unique way of escaping predators – and scientists – but that hasn't stopped researchers from studying the lizards. And now they have named the first new species in 75 years.

This composite image shows Geckolepis megalepis with its scales (l.) and after shedding its scales (r.).
Images courtesy of Frank Glaw
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Caption

If you try to catch a Geckolepis, you might find yourself left with just a handful of scales as a naked gecko wriggles away to safety. 

The Madagascan lizards have large, fish-like scales that they shed when encountering friction, like that of a predator's mouth or a scientist's hand. But don't worry about the scale-less lizards: the geckos don't stay denuded forever. The scales regenerate within weeks.

Researchers have known about these weird lizards for 150 years, but their evasive maneuver means they have proved tricky to study. But scientists have kept at it. Now some researchers have figured out a way to identify new species in the genus – and, for the first time in 75 years, a team of scientists has named a new Geckolepis species. 

Geckolepis megalepis, as the researchers name the lizard in a paper published Tuesday in the journal PeerJ, has larger scales than the other known members of the genus.

"This may mean that it's easier for it to escape from predators than for related species that have considerably smaller scales," says study lead author Mark Scherz, a herpetology PhD candidate at Ludwig-Maximilians Universität and Zoologische Staatssammlung, München.

Or perhaps it has the opposite effect, he says in a phone interview with The Christian Science Monitor. To explain this idea, Mr. Scherz likens the geckos' large scales to sticky notes. The greater the surface area that's sticky, the greater the force required to peel it off from whatever it's stuck to.

Describing new species isn't just about finding fascinating life-forms among us. It could also help save critically endangered animals. "Every time that we describe a new species, we give a little bit of hope for the conservation of that species," Scherz says.

For these Madagascan geckos, there might be a ticking clock. "Deforestation is so rampant" there, Scherz says, that much of the diversity on the island is critically endangered.

And scientists think many Geckolepis species live only in tiny, fragmented regions on the island. So if those environments are obliterated, the weird lizards could be, too.

But understanding the diversity of Geckolepis species could help scientists and conservationists figure out how to best save the enigmatic lizards and their world.

Scherz and his colleagues actually identified G. megalepis as a new species by studying its bone structure. Because the geckos are so difficult to study alive and with all their scales on their bodies, the team micro CT scanned preserved museum specimens.

They knew from a 2013 genetic study of the genus that there should be about 10 genetically distinct members of Geckolepis, perhaps more. But only four species had been identified. That's why they turned to the morphology of the animals to find features that would help sort out distinct species.

Taken with that genetic data, this new research provides "overwhelming evidence that this thing is new," Tony Gamble, an evolutionary biologist at Marquette University who was not part of the study, says in a phone interview with the Monitor.

And, according to the genetic data, there could be five or perhaps more Geckolepis species yet to be named.

Anthony Russell, a professor emeritus of biology at the University of Calgary, says he is not really surprised by the new research. "It adds a lot of detail about the fine points of skeletal structure, but this is only of direct interest to those who use such data for classificatory purposes," he writes in an email to the Monitor. The details identified by Scherz and his colleagues, Dr. Russell says, are largely minutiae, and a larger sample size of specimens would be required for the researchers to really identify the variation that distinguishes species.

The team did scan specimens across the group, as they were hunting for other clues to compare against the genetic data from 2013. There was some confusion as to which clade one of the other species, Geckolepis maculata, belonged. Researchers thought that G. maculata belonged in the AB clade, but the new osteological data revealed that the skeletons of the Geckolepis specimens that belong to that clade are "totally different from maculata," Scherz tells the Monitor in a phone interview.  

Scherz hopes an osteological survey of the whole genus will help reveal exactly where G. maculata belongs.

The team also noticed a few characteristics of Geckolepis skeletons that are rare in other geckos, which may help them identify specimens belonging to the genus in the future. Although this won't help scientists identify the geckos in the wild, it will help them amass larger sample sizes to study in the laboratory.

"The genus has always been difficult to work with and species boundaries have been vague, leading to taxonomic confusion," Aaron Bauer, an integrative biologist at Villanova University who was not involved in the study, writes in an email to the Monitor.

Dr. Gamble says the use of micro CT scanning could be used in the future to help resolve questions about mysterious animals more generally. "I'm pretty confident that this will be used more frequently" as the technology becomes cheaper and more user-friendly, he says. One major benefit: the technique allows researchers to see specimens that may have been gathering dust in museum collections in a different light. "If you look on their insides, you're able to look at a whole new array of characteristics of these organisms," Gamble explains. 

But others are more skeptical about the osteological method. "Micro CT scanning is a neat tool, but it tends to seem to deliver because of the 'high tech' nature of the approach, rather than because it really reveals 'new' things," Russell says.

For Gamble, however, any tool to help discover new species is important. "There are still a shockingly large number of species left to be described" to fully understand the diversity of life on Earth, he says, and more than 30 new species of gecko alone are described each year. "In aggregate, that's a shockingly large number of new species every year in just one little branch of the tree of life."

Geckolepis isn't the only genus of gecko to have these strange, tear-away, regenerating scales. The first time Gamble had a freshly-denuded lizard (which he says looked somewhat like raw chicken) slip out of its skin in his hand, it was actually a Madagascan day gecko. 

"It totally works," he says of the animal's great escape. "I let the lizard go because I was so shocked."

But geckos are well-known for other surprising loss and regeneration of body parts. Most famously, some lose and subsequently regrow their tails to escape a threatening grasp.

Others, including Geckolepis, have "regional integumentary skin loss," Dr. Bauer points out, and such skin regeneration could reveal key insights for medical innovation.

"Although the authors wax lyrical about the enlarged and mineralized scales, they missed an opportunity to really investigate their structure," Russell says. "The detailed structure of the scales, and the tissues that they contain, would be the most novel way to go with this research topic, because it would have a much broader significance to those who study the structure of skin in general." In fact, that sort of research is already being done on other geckos.

Scherz agrees that these geckos could be important subjects of regeneration study, but his focus is "to provide the first knowledge, the baseline" of understanding of these animals and other researchers who focus on the cellular level can take it from there.

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