#SciFri: Why do snakes shed their skin?
As someone that studies reptiles and snakes in particular, I’m often asked why reptiles shed their skin. Before I answer that question, let’s take a step back. When some people picture a reptile shedding their skin (also called sloughing), they see a snake or a lizard shedding their skin with all layers intact kind of what you see with snakeskin handbags. However this is not what happens, both reptiles and amphibians only shed the outermost layer of their skin that contains dead keratised cells that once acted as a barrier between them and the outside world. We do a very similar thing but instead of shedding our skin in one go, we shed individual cells as flakes. To shed their skin, reptiles will rub up against an abrasive surface such as a rock or rough grass, initiating the sloughing process.
Now that we’ve covered the basics, why do reptiles and amphibians shed their skin? There are two main reasons for this with the first one being growth. As I’ve already mentioned, this outer layer of skin is dead and so doesn’t continue to grow as the body of the animal does. In order to allow continued growth, the animal must cast of it’s old skin ready for a more spacious one to develop which the animal can grow into. I like to think of this a growing child outgrowing their clothes, it’s a similar concept. There is always an exception to the rule and one such example is the gecko Geckolepis megalepis which was described in 2017, which can shed it’s scales in order to escape a predator. You an read more here.
The second reason is that it allows the animal to more easily shed any exoparasites, which live on the surface of the host. These could be ticks or mites, that may otherwise be too difficult to remove (especially if you’re a snake with no limbs). The act of shedding the skin may also help the animal to remove any infected cells of diseases such as chytridiomycosis and ophidiomycosis. This may allow them to stay one step ahead of infection therefore preventing disease or escaping it all together. The skin is an important barrier with the environment and so needs to be maintained to ensure that it operates as needed.
You may have seen the sloughed skins of reptiles such as snakes and lizards in environment when in the field. If you have (and you live in the UK) then please consider submitting them to the Reptile Database operated by the Amphibian and Reptile Conservation Trust, more information can be found here. So what about amphibians, why don’t we find their old discarded skin in the environment? Sometimes you may be lucky enough to, floating on the top of small ponds with an abundance of newts. However in most cases, the animals eat them as they are shed (some reptiles will also do this).
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