Cut & Run: Autotomy in Lizards
(Lizard engaging in tail autotomy)
We recently posted a lizard dissection video (which you can check out here), where we explained the anatomy and physiology of these fascinating reptiles. Although we briefly mentioned this in the video, would you believe me if I told you that lizards can detach and regrow their tails as a means of self defense? That’s right. Lizards can engage in a behavior called autotomy, where they are able to discard & regrow their tails.
So how exactly do lizards detach their tails? Well lizards are born with a line of weakness –called fracture planes– across each vertebra of their tail. When a point on the lizard’s tail is stressed or takes a hit (often due to an attack by predators), the muscles lining the fracture plane pull away from each other –a response known as a reflex muscle spasm– causing the tail to detach from the lizard along the fracture plane at which the physical stimuli was inputted. After such breakage, the sphincter muscles contract around the caudal artery in order to minimize bleeding, and skin flaps fold over the wound present at the site of autotomy in order to close the wound & prevent infections. Most species of lizards are then able to regenerate the tail, but every tail regenerated after the initial tail is made of cartilage instead of bone.
There are a couple ways in which autotomy helps lizards defend against predators. First, if the predator had gotten hold of the lizard by its tail, the breaking off of the tail allows the lizard to flee from the predator. Adding onto that, in many species of lizards, the detached tail continues to move for ~30 minutes, giving a deceptive sense of continued struggle, distracting the predator while the lizard escapes the scene. The fact that many species of lizards have vibrantly colored tails also helps with the deception factor.
However, as with all good things, there are drawbacks with autotomy. Decreased social standing and mating ability after autotomy has been observed in many species of lizards, and in Texas banded geckos the ability to produce eggs is greatly reduced upon engaging in autotomy. Adding onto that, autotomy usually comes at a great cost to the immune system, decreasing the lizard’s ability to fight off parasitic organisms and infections. The tail also contains a lot of fat deposits (i.e. it is a big energy store), which can cost the lizard dearly upon frequent autotomy. Because of these reasons, despite its effectiveness, autotomy is mostly used in lizards as a last resort, when all other means of self defense have failed. There’s a life lesson in here somewhere, right?