Spiny mice have armor in their skin

Spiny mice are called so because of the needles that cover their backs. The needles are real, like those of hedgehogs. They also have amazing skin that separates from the body very easily. In a moment of danger, spiny mice easily leave pieces of skin to the enemy who grabbed them, just as lizards throw off their tail. Spiny mice can afford it: their skin regenerates extremely quickly, and regenerates much better than a lizard’s tail.

The oddities of spiny mice do not end there. Staff at the University of Florida write to iScience about bones in the skin, or, more precisely, secondary skin ossifications, which are also called osteoderms. These are really real bones, only small and flat, immersed in the thickness of the skin. Osteoderms were common in dinosaurs and other extinct reptiles. Of modern animals, “skin bones” are well developed in crocodiles, and some lizards and sand boas also have them; some elements of the turtle shell are formed from osteoderms. And there are also armadillos – their armor is formed by numerous plates of skin ossifications.

In spiny mice, the osteoderms sit in the tail. They were discovered because museum exhibits of mice were scanned by X-rays as part of a project to create three-dimensional models of various animals. After the museum exhibits, the researchers set to living mice – to understand how these bone plates develop in them. It turned out that they develop from the base of the tail to its end, and that in newborn mice, the genes that control bone formation are very active in the skin cells of the tail – which, perhaps, was to be expected.

Reconstruction of the body of a spiny mouse with a skeleton and a tail protected by bony plates in the skin. (Illustration: Edward Stanley, Florida Museum of Natural History)

So spiny mice became another group of animals that, at the whim of evolution, developed – if only on the tail – reptilian skin armor. Most likely, here we are also talking about protection: a predator, grabbing a mouse by the tail, will pull the skin off it, but the tail itself will remain intact. Although, as the portal writes ScienceNews, it may not be predators at all: spiny mice are known to regularly bite each other’s tails, and not necessarily in a fight – we are probably talking about some form of communication. And so, in order not to bite off each other’s tails while communicating, the mice acquired tail armor. Well, about the study itself, we can say that this is another example of how you can discover something new without leaving the museum rooms.