Cosmo
Hey, Dr. Universe. What kind of photos do turtles take?
Dr. Universe
I don't know. What kind?
Cosmo
Shell-fies!
Dr. Universe
Hey, friends. I'm Dr. Universe.
Cosmo
And I'm Cosmo.
Dr. Universe
And today we're talking about a question sent in by a kid like you. Malachi wants to know: Do turtles live inside their shells?
Cosmo
In cartoons, turtles just pop out of their shells and run around. Is that real?
Dr. Universe
That's what I asked my friend Ryan Wagner. He's a wildlife biologist at Washington State University. And he told me absolutely not. Turtles can never leave their shells because they are their shells. The shell is their body.
Cosmo
Whoa! So, the shell isn't like a house that they carry around?
Dr. Universe
Not at all. You may have seen a hermit crab climb out of a seashell, but it's not like that for turtles. A turtle's shell is made of their bones—like their backbone and ribcage.
A turtle's ribs grow wide and flat and fuse together to make a solid shell. The turtle's collarbone, shoulder bones, and pelvic bones are tucked inside the ribcage. As the turtle grows, its shell grows, too—just like our bones do.
Cosmo
Okay, but wait. How does the shell form in the first place?
Dr. Universe
It's like our skeletons. The shell starts forming when the turtle is still an embryo inside an egg. The shell starts out soft and then hardens as the baby turtle grows.
If you look at a turtle's shell, you'll see it has two parts. The dome on the back is called the carapace. The belly plate is called the plastron. Those two pieces connect at the turtle's sides. The turtle's head and front legs stick out the front. Its tail and back legs stick out the rear. Together, they protect all the turtle's mushy internal organs.
Cosmo
If the shell is part of its body, does that mean a turtle can feel it when I touch its shell?
Dr. Universe
Yes. A turtle's shell is full of nerves that are connected to its spinal cord. So, it's super sensitive.
Cosmo
Wow! That makes me think twice about touching one.
Dr. Universe
Yeah. It's usually not a good idea to touch wild animals. But if you did gently touch a pet turtle, you'd feel that the shell has an outer covering. Many turtles have keratin plates there called scutes. Keratin is the same protein that makes up your fur and claws. Or a human's hair and fingernails. Some turtles have a leathery shell covering instead.
Cosmo
So, if turtles can't climb out of their shells like I see on cartoons, can they hide inside their shells?
Dr. Universe
Some turtles can. They have a hinged belly plate that flexes up and down. So, they pull their head, legs, and tail inside their shell. Then they use their muscles to squeeze the plastron and carapace together to make a tight seal.
Cosmo
That's a super smart way to hide from predators.
Dr. Universe
Totally! But it can make things tricky for scientists like Dr. Wagner. He told me that he had a job in college clipping turtle toenails. They used the clippings to measure how stressed out the turtles were. But the turtles could pull in their heads and legs and clamp their shells shut. So, he couldn't get to their toenails.
Cosmo
Ha! That probably gave him stress.
Dr. Universe
I bet. But that kind of work is super important because turtles are in trouble. There are about 350 species of turtles in the world, and about half of them are at risk of extinction. They might be some of the most endangered animals on the planet.
Cosmo
Oh no.
Dr. Universe
Yeah. Turtles need our help. We can protect their habitats and leave wild turtles alone. It's also really important to never release a pet turtle into the wild.
Cosmo
Because they're spe-shell animals.
Dr. Universe
That's all for this episode, friends.
Cosmo
Big thanks to Ryan Wagner, wildlife biologist at Washington State University.
Dr. Universe
As always, if you've got a science question for me, you can submit it at askdruniverse.wsu.edu. That's A S K D R U N I V E R S E dot W S U dot E D U.
Who knows where your questions will take us next.
