Geckolepis megalepis without scales Geckolepis megalepis sheds its scales to flee danger, and can regenerate them in a few weeks. (Photo: Frank Glaw/PeerJ)

Lots of lizards detach their tails to flee predators, a defense mechanism known as autotomy. But one group of geckos from Madagascar and the Comoro Islands goes a different route: When they sense danger, they literally jump out of their skin.

Known as fish-scale geckos, these lizards have large scales that quickly detach when they encounter friction, letting the rest of their soft, pink bodies scurry away. Even a slight touch can trigger this reaction, which helps the geckos escape a predator's clutches before it's too late. The wily reptiles may be unsightly and vulnerable in this state, but they grow new scales within a matter of weeks.

This trick likely evolved to thwart predators like snakes, although it works pretty well on scientists, too, making the geckos a challenge to study. Nonetheless, a team of researchers just discovered the first new species of fish-scale gecko in 75 years. Named Geckolepis megalepis, it has the largest scales of any known gecko, "which come off with exceptional ease," they report in the journal PeerJ.

Off the scales

Geckolepis megalepis with scales Geckolepis megalepis in more formal attire. (Photo: Frank Glaw/PeerJ)

Fish-scale geckos belong to the genus Geckolepis, a group of nocturnal, arboreal insect eaters native to Madagascar and the nearby Comoro Islands. While they've been known to science since 1867, their elusiveness has often hindered research. Scientists once used bundles of cotton wool to catch them without losing too much skin, but now try to avoid any contact, instead luring them into plastic bags.

Even once they're caught, the geckos are still "a nightmare to identify," says Mark Scherz, lead author of the new study and Ph.D. student at Ludwig Maximilian University of Munich and Zoologische Staatssammlung München. Geckolepis was long divided into just four species, but recent genetic research has hinted at more, tempting Scherz and his colleagues to take a closer look.

fish-scale gecko A different fish-scale gecko species at Ankarafantsika National Park. (Photo: Frank Vassen/Wikimedia Commons)

"A study a few years ago showed that our understanding of the diversity of fish-scale geckos was totally inadequate," Scherz says in a statement, referring to a 2013 study. "It showed us that there were actually about 13 highly distinct genetic lineages in this genus, and not just the three or four species we thought existed. One of the divergent lineages they identified was immediately obvious as a new species, because it had such massive scales. But to name it, we had to find additional reliable characteristics that distinguish it from the other species."

The researchers ended up using micro-CT scans to search the gecko's skeleton for identifying traits, finding a few skull features that helped confirm it's a new species. But as Scherz explains, the real beauty of this bizarre lizard is only skin-deep.

"What's really remarkable," he says, "is that these scales — which are really dense and may even be bony, and must be quite energetically costly to produce — and the skin beneath them tear away with such ease, and can be regenerated quickly and without a scar." The mechanism for this ability isn't well understood, the researchers say, but it's worth studying for more than just academic interest. It could have applications in human medicine, for example, where regeneration research is already informed by the science of salamander limbs and lizard tails.

deforestation in Madagascar G. megalepis may be threatened by fires and deforestation, scientists say. (Photo: Dudarev Mikhail/Shutterstock)

It's still unclear how abundant the newfound gecko is, but according to National Geographic, they may face threats from sapphire mining, free-ranging livestock and fires caused by human activity. Deforestation is also "rampant" in Madagascar, as Scherz tells the Christian Science Monitor, and already threatens much of the island's rich biodiversity. Going nude might save this lizard from hungry snakes, but it's little help with habitat loss. Identifying new kinds of wildlife doesn't just fascinate and benefit humanity; it's also the first step in protecting those creatures from ourselves.

"Every time that we describe a new species," Scherz says, "we give a little bit of hope for the conservation of that species."