How does a turtle’s shell grow?

Written by Hooi Cheen Teng

Cheen Teng is a Biology student at the University of Sheffield. In 2023, she undergoes an internship at TCS to gain experience working in the field of wildlife conservation.

16 Jul 2023

A turtle’s shell is its most recognisable feature. It is made up of around 60 different bones, which are held together by ligaments, muscles, and tendons. As the shell forms part of a turtle’s skeleton, it cannot leave the shell, and the shell grows along with it as it ages.

The carapace and plastron of a turtle, which are the upper and lower parts of the shell, consist of bony plates covered in scutes made of keratin. To accommodate for the increasing size of a turtle’s body, new, wider scutes grow beneath the existing scutes, which are then shed to make way for the new ones. Besides allowing the shell to grow bigger, this has other benefits, such as the removal of algae or infections that are present on the old scutes. If these are not dealt with, they could lead to shell rot, which can be fatal. Additionally, the replacement of damaged scutes can help turtles to maintain their streamlined shape. The bone underlying the scutes has limited regenerative power, much like the bones of humans.

With every shedding of the scutes, an additional ring will be present on the newly exposed scutes. As a result, the rings on a turtle’s shell can be used to estimate its age. While the size of the scutes increases, the number of scutes remains the same as it grows.

It is important that a turtle’s shell grows as it ages, as it is essential for protection against predators. The shell will continue to grow until a turtle reaches its full size.


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  3. Scientific American. (23 October 2006). How are seashells created? Or any other shell, such as a snail’s or a turtle’s? Retrieved 16 July 2023. Link.
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