Gecko skins itself to escape predators

Some of you may find this gross, but it’s still a remarkable achievement of natural selection, and one of those weird things that abound in nature but most of which are yet to be described.  It’s the discovery of a “fish-scale” gecko that easily sheds its scales when caught, revealing a bizarre, naked reptile that has to regrow its scales but which has escaped predation. That’s a worthwhile tradeoff!

The animal was described in a new paper in PeerJ by Mark Scherz et al. (reference below; free download), and has been publicized widely on Twitter by astonished biologists, as well as in a short piece in The New York Times

Geckos are lizards in the family Gekkota. The genus Geckolepis, which contains about ten species endemic to Madagascar and the Comoros Islands, are known as “fish-scale geckos” because they have large scales that are shed easily. Presumably, they lose many of their scales, including a portion of their skin, when seized by predators, allowing them to escape.

The new paper tries to resolve the number of species (or “operational taxonomic units”) in the group, but the cool part is the description of a new species, Geckolepis megalepis—the first new species described in this genus in 75 years. Most of the paper is full of arcane details of its anatomy and morphology (needed to describe a new species and distinguish it from existing ones), but we needn’t be concerned with most of those. Here’s what the new species looks like:

08tb-gecko1-master768

Geckolepis megalepis, newly discovered in Madagascar, has the largest scales of any fish-scale gecko. Credit Frank Glaw

What is novel about G. megalepis is that its scales are relatively larger than those of any other fish-scale gecko: the authors say that if we were covered with scales of the same relative size, they’d be the size of our hands. These scales, which are highly mineralized, are shed easily when the animal is grabbed; in fact, the researchers had to catch the animals with wads of cotton to try to preserve them intact.  Below are some quotes from the paper:

Geckolepis megalepis was observed active at night both in the rainy and dry seasons, on trees and tsingy limestone rock. When captured, these geckos showed a strong tendency to autotomize [shed] large parts of their scales, leading to partly ‘naked’ geckos without any visible (bloody) lesions. In a subjective comparison this tendency appeared to be even more developed than in other Geckolepis species.

And this is what one looks like after it’s been grabbed and released; one of the authors describes the scale-denuded beast as looking like a “naked chicken breast.”:

132206-gecko-1

For those of you who want more gory detail, read on (I’ve divided one long paragraph into three), for it’s not just the scales that are shed (my emphasis):

Many reptiles have evolved the ability to shed some part of their body in response to predator attack. The most widespread form is caudal autotomy, the shedding of all or part of the tail, which is widespread among Lepidosauria, from amphisbaenians to rhynchocephalians, even being found in some snakes (Arnold, 1984; Bateman & Fleming, 2009).

Geckolepis species are also able to shed their tails, and indeed few specimens survive to adulthood with their original tails intact (see for instance Figs. 3A and 3B). In addition, these geckos have evolved an even more extreme adaptation, i.e. the autotomy of virtually their entire integument when seized or even touched. Earlier studies have shown that the autotomized layers include epidermis, underlying connective tissue, and subcutaneous fat tissue, and that a layer between the integument and the underlying tissue represents a pre-formed splitting zone (Schubert & Christophers, 1985).

The shedding process is most likely achieved by contraction of the network of myofibroblasts in the preformed splitting zone, with vasoconstriction in the most superficial vasculature of the dermis to avoid bleeding (Schubert & Christophers, 1985). This process is thus completely different from the normal skin shedding of squamate reptiles, which leads to a loss of keratinized epidermis only (Schubert & Christophers, 1985) The scarless regeneration of the whole integument occurs within a few weeks, apparently starting from stem cells of the deeper layers of the connecting tissue and is considered as unique among vertebrates (Schubert, Steffen & Christophers, 1990). Superficially, no differences are apparent between regenerated and original scales, due to the irregularity of scalation patterns and some variability in scale size. The same is true for regenerated tails; indeed, it is often hard to be certain that a Geckolepis tail has been regenerated without X-ray images showing that the vertebrae are absent.

But does this presumed defense against predators really work? Well, predation events are hard to see, but at the end of the paper the authors describe one observation of a related species grabbed by a larger gecko, and in that case “the Geckolepis individual [not the new species] slipped from the mouth of the Blaesodactylus [big predatory gecko] ca. 30 seconds after being captured, and escaped denuded, thereby providing the first direct evidence of successful escape by skin shedding.”

Well, it would be good to have more observations, but I suspect that the loose scales and integument have indeed been molded by natural selection to resist predators. These animals pay a big cost in having to regenerate their scales, which must be a big metabolic expense, and they’re also denuded for much of that time, making them more vulnerable. But that’s a smaller price to pay than being ingested by a predator!

h/t: Nicole Reggia

____________

Scherz, M. D., J. D. Daza, J. Köhler, M. Vences and F. Glaw. 2017.  Off the scale: a new species of fish-scale gecko (Squamata: Gekkonidae: Geckolepis) with exceptionally large scales. PeerJ 5:e2955; DOI 10.7717/peerj.2955

24 Comments

  1. Posted February 10, 2017 at 11:23 am | Permalink

    That is astonishing. How long exactly does it take for their scales to be restored?

    • Shaokang Yuan
      Posted February 10, 2017 at 12:03 pm | Permalink

      See the third to last paragraph.

  2. Randy schenck
    Posted February 10, 2017 at 11:24 am | Permalink

    I saw this reported on the news yesterday. It does have a bit of that gross factor but whatever works to survive.

    • jaxkayaker
      Posted February 11, 2017 at 5:58 pm | Permalink

      Exactly. Survival of the fittest is survival of whatever works.

  3. Barry Lyons
    Posted February 10, 2017 at 11:28 am | Permalink

    This is crazy! What will the natural world think of next? Amazing.

  4. eric
    Posted February 10, 2017 at 11:58 am | Permalink

    Earlier studies have shown that the autotomized layers include epidermis, underlying connective tissue, and subcutaneous fat tissue…

    The scientist who figures out how to incorporate the ability “loses subcutaneous fat when grabbed” into humans is going to make billions.

  5. Posted February 10, 2017 at 12:13 pm | Permalink

    Sure it sheds scales and escapes predators…but can it sell insurance?

    • E.A. Blair
      Posted February 10, 2017 at 12:36 pm | Permalink

      I’d like to see this incorporated into one of their commercials.

  6. Mark R.
    Posted February 10, 2017 at 12:19 pm | Permalink

    Very beautiful gecko (when not nakit), the scales look like mother-of-pearl. A truly amazing escape mechanism and it looks painful…but maybe natural selection has solved that problem too.

  7. rickflick
    Posted February 10, 2017 at 12:54 pm | Permalink

    It’s clever as they come. It’s like trying to wrestle someone who’s wearing a loose shirt.

  8. Posted February 10, 2017 at 1:06 pm | Permalink

    Very interesting – and cute as well!

  9. Gregory Kusnick
    Posted February 10, 2017 at 2:43 pm | Permalink

    the authors say that if we were covered with scales of the same relative size, they’d be the size of our hands.

    This kind of comparison sets my teeth on edge. If human hair were the same relative size as mouse hair, it would be as thick as phone charger cords. But guess what? It isn’t, because big organisms are not just scaled-up versions of small organisms. Different constraints apply at different scales.

  10. Paul S
    Posted February 10, 2017 at 2:46 pm | Permalink

    Cool. I wonder what they do for the few weeks until the scales grow back. That may have been answered in the paper, but I was unable to download it.

  11. Lars
    Posted February 10, 2017 at 3:53 pm | Permalink

    Geckos in general exhibit fast, thorough healing of epidermal wounds. A researcher I know was taking skin plugs from the backs of leopard geckos as part of a project on regeneration. When they went back to re-sample the geckos, they couldn’t tell where the original plugs had been taken – complete and seamless regeneration of the colour pattern the scalation, the lot.

  12. amyt
    Posted February 10, 2017 at 5:57 pm | Permalink

    On a stick, yum!

  13. ToddP
    Posted February 10, 2017 at 9:05 pm | Permalink

    Fascinating behavior. Those enlarged scales make for a strange looking gecko. It reminds me of the shield from the old ’80s movie Dragonslayer.

  14. Posted February 10, 2017 at 11:06 pm | Permalink

    +1

  15. nicky
    Posted February 10, 2017 at 11:26 pm | Permalink

    Another wonder from Madagascar, that island is definitely on my bucket list.

  16. Mike
    Posted February 11, 2017 at 8:26 am | Permalink

    A strange little Beast.

  17. Posted February 11, 2017 at 5:53 pm | Permalink

    Thanks for the report. This will make a nice example for my Comparative Anatomy class.

  18. jaxkayaker
    Posted February 11, 2017 at 5:59 pm | Permalink

    very cool, very interesting. I wasn’t aware of these geckos, despite a long interest in herpetology.

  19. Posted February 11, 2017 at 7:30 pm | Permalink

    Living in Indonesia in my childhood and youth, I enjoyed the unavoidable company of geckos at night, specially attracted by the lights on verandas. Friendly animals, called “to-keh” (the ‘e’ being pronounced as in ‘end’), an onomatopeya of the sound they emitted. We admired their ability to let go their tails and continue living happily thereafter.
    .-

  20. Posted February 13, 2017 at 7:04 am | Permalink

    I just wanted to point out that we did not catch these animals with cotton bundles; this has been widely misinterpreted by the press. We catch the geckos either by chasing them into plastic bags or other containers, or rarely by hand. The cotton bundle method is from the 1800s. 🙂
    Thanks for covering our discovery!
    Cheers,
    Mark


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