QotW - Do other animals get itchy?
Margaret wrote in to ask: "Science has now identified actual nerve endings that humans and other mammals have that transmit itchy feelings to the brain. Do snakes or amphibians have these same nerve types? Have frogs been seen scratching an itch?"
Harry Lewis spoke to Gerhard Schlosser from the National University of Ireland Galway to find out more...
Gerhard - We’re all itching to know! The truth is that the itch has only been studied in humans and a handful of other mammals. We all know it as a rather unpleasant sensation, it makes us want to scratch. And just like pain, it actually acts as a warning signal, alerting us to dangerous conditions. The want to scratch can be quite beneficial, helping to remove objects that cause irritation. So, through evolution, our perception of the itch has probably allowed us to defend ourselves from bugs, weeds and germs that attack our skin.
Harry - We perceive ‘the itch’ with sensory nerve cells that spread into the skin where they form free nerve endings.
Gerhard - There are different subtypes of such sensory cells, each of which specialized for a different stimulus. Apart from sensory cells that respond to touch or to temperature, there are those that are activated by tissue damage which we perceive as pain, and those that react to skin irritation encouraging the individual to scratch. We have all seen mammals, like horses and dogs rubbing their backs and sides against an object to remove annoying flies or ticks! But these multiple subtypes of sensory nerve cells are also found in other vertebrate animals – that is animals with a backbone - such as fish or frogs.
Harry - In short, we don’t know for sure whether any of them feel the same itch sensation that we experience, but we might be able to make an educated guess, afterall many vertebrate animals are known to scratch or rub themselves when their skin is irritated.
Gerhard - A recent study even found sensory cells in zebrafish that carry the same receptor molecules on their surface as human itch receptors. This suggests that fish, like mammals, can perceive it, they do get itchy. And because this receptor molecule is so widespread we can almost assume that it originates from a common ancestor. An ancestor that passed the same itch down to amphibians as it did zebrafish. I think it’s safe to say that although more research is needed, frogs get the urge to scratch their itches, just like us.
Harry - Now, all I can think about is that one point in my back I can’t reach, you know the patch. I’d need frog legs to get to it.