- We don’t know what you know, but a turtle can’t get out of its shell, just like we can’t “get out” of our bones.
- In fact, the shell is part of a turtle’s skeleton, composed of a rib cage, vertebrae and sternum.
- But if you could look inside a turtle shell, you would find some of the most unusual features in the animal kingdom.
- Turtle shells are specially designed to prevent the buildup of lactic acid, which is a byproduct of anaerobic respiration.
This is the transcript of the video.
Narrator: A turtle’s shell is as much a part of its body as our rib cage. In fact, it’s its rib cage, and its spine, and its vertebrae, and its sternum. Basically, a turtle’s skeleton is inside out. And, just like you can’t take a human skeleton off, you can’t separate a turtle from its shell either. But if you could, you’d probably be surprised by what you discovered.
Maria Wojakowski: This is the inside of a turtle.
NarratorThis is Maria Wojakowski, a biologist who has studied the nature of turtles for more than a decade. This is her shoulder girdle. This is her hip.
Narrator:See how the hips and shoulders fit inside the turtle’s ribcage? Turtles are one of the only land animals on the planet with this feature. They are also one of the only animals that can breathe through their butts. Inside the turtle’s shell there is a very particular respiratory system.
Wojakowski: Here you can see the lungs in this direction.
Narrator: Now, most land animals breathe by expanding and contracting their ribs, which creates a natural pump that guides air in and out of the lungs. But turtles can’t do this because their shells are rigid and don’t expand. So instead, they rely on sheets of muscle inside their shell to pump oxygen out through their mouths. That is, most of the time. Then there are other times when turtles exhale at the other end. It’s the same opening that turtles use to urinate, defecate, and lay eggs. And in some cases, they can double as a set of gills, sucking in water and absorbing the oxygen it contains. Scientists think turtles do this when they spend long periods of time underwater, like when they’re hibernating.
And if you look closely at the inside of a shell, you’ll discover another feature that helps them hibernate underwater: a scaffold-like structure that can store and release chemicals. This structure actually helps turtles breathe without oxygen.
Read more: The elephant’s trunk is like a human’s tongue, arm and nose combined into one super organ
Here’s how it works: Many turtles hibernate in frozen ponds that lack oxygen, and in order to survive, their metabolism switches from aerobic to anaerobic. This means they stop using oxygen for energy and start using glucose instead through a process called anaerobic respiration. And the byproduct of that is lactic acid. Now, theoretically, this acid could build up in the turtle’s body and kill it.
That’s where the shell’s structure comes in. It can absorb lactic acid as well as release bicarbonate to neutralize that acid. It’s like a stomach antacid for turtles. So, it turns out that having a shell is actually very useful in certain situations. In fact, scientists think that turtles originally developed their shells for digging, probably more than 200 million years ago.
Wojakowski: They excavate very, very complex underground structures.
Narrator:And of course, shells are incredibly useful for defending against predators, no matter how fierce. Turtles are amazing.
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