Date:10 February 2017
Researchers have introduced a new gecko species with a remarkable survival tactic. Geckolepis megalepis is so named because of its unusually large scales. They fall off easily, along with the animal’s skin, leaving any would-be predators with a mouth full of scales and the gecko naked, but alive.
Reptile species are typically differentiated by their scale patterns, but the ease with which G. megalepis lose their scales made officially designating them as a species difficult. So the authors turned to micro-CT technology to generate 3D images of the geckos’ skeletons without harming the animals. This revealed some skull features that distinguish G. megalepis from other geckos, cementing their status as species unto themselves. Study author Mark D. Scherz of the Zoologische Staatssammlung München tells us more about these animals and their easily discarded scales.
ResearchGate: What is Geckolepis megalepis and how was it discovered?
Mark D. Scherz: As is often the case, it was not clear that G. megalepis was a new species when it was discovered back in 2004. The realization came only after genetic data from the whole genus Geckolepis were collated, and it was revealed that there were at least twelve distinct genetic lineages, not three as was previously thought. The most different of these was one with larger scales than the others, and it is this clade that we have now described as G. megalepis, a name that derives from this remarkable feature.
Geckolepis megalepis is found in Ankarana National Park, a limestone karst in northern Madagascar. This karst is difficult to navigate, so the animals that live there are hard to access and study. It is no coincidence that the last few years have seen the discovery of numerous new reptile and amphibian species from this area of Madagascar. Geckolepis megalepis now joins their ranks, but more are certain to come.
RG: How are its scales different from those of other geckos?
Scherz: First of all, they are overlapping. This is a characteristic of the genus Geckolepis that sets them apart from all other geckos except the middle-eastern Teratoscincus, to which they are not related. In addition, the scales are partly ossified—there are dense, bony structures throughout the scales that make them appear dense in micro-CT scans.
But what is most remarkable about Geckolepis scales is that they come off with extreme ease. The skin underneath them contains a layer of myofibroblasts that presumably contract, separating the skin and scales from the underlying tissue. This is essentially the same for all Geckolepis species, but what sets Geckolepis megalepis apart is that its scales are much larger than any other we know. In fact, it has the largest scales in the absolute sense of any known gecko. Its scales come off particularly easily, which we hypothesize may be due to the greater leverage and friction forces that accompany their larger diameter and surface area.
It is also worth noting that these geckos can regenerate their scales within a matter of weeks. As far as we can tell, the regeneration is scarless, and the regenerated scales are indistinguishable from original ones. That is not the case with many other geckos, whose regenerated scales have a distinctly different appearance than the original ones.
RG: What’s the advantage to the gecko of having scales that come off easily?
Scherz: This is clearly an adaptation for predator evasion; the teeth or claws of a would-be predator might become lodged in the scales of the geckos without making it through to the underlying flesh. This results in the skin tearing free, leaving the predator with a fist or mouth full of scales, while the gecko escapes, denuded but alive.
RG: What’s the skin under the scales like? Is it enough to protect the animal while the scales grow back?
Scherz: This is not clear. What we do know is that what’s left behind is not skin, but rather connective tissue; the whole skin is lost, and must re-grow. That means that specimens that have lost their scales are probably more susceptible to dehydration, and we suspect that they then seek humid shelter until the regeneration process has at least begun.
RG: Do the scales coming off easily pose any challenges when researching them?
Scherz: Counting scales is the absolute standard for identifying most reptile species. Geckos, generally, are no exception, although some have such small scales that counting has been largely abandoned in favor of other techniques. The problem with Geckolepis is that either the scalation of the animals is incomplete, or it has changed at some point over the life of the specimen. This makes scale counts for them less reliable, so we have turned to micro-CT in order to help in the taxonomy of the genus. While it is true that Geckolepis megalepis has much larger scales than any other species, and is therefore immediately recognizable even from photographs, the same cannot be said of the other genetic lineages in this genus.
Image credit: Frank Glaw
This article was originally written for and published by ResearchGate.