Turtles are one of the oldest groups of reptiles.
These fascinating creatures have remained unchanged for over 200 million years.
One thing that sets them apart from other reptiles is their unique shells. But, there is a lot of misinformation floating around about turtle shells. Even scientists aren’t 100% sure about their evolution.
This general confusion has led to myths, like the idea that turtles can easily remove their shells.
Do you know why turtles can’t remove their shells?
Keep reading to learn the fascinating biology behind a turtle’s shell…
Turtle Shells
A turtle’s shell is made from a series of bony plates called scutes.
These scutes are covered in a hard horn-like material made of keratin.
While the shell is as hard as a rock, that doesn’t mean that they can’t feel anything. The shell is a living bone, just like our skeleton. It has nerve endings that allow them to feel when their shell is touched!
Their shell is actually a combination of the sternum, rib cage and vertebrae.
It has two main parts: the carapace and the plastron.
The carapace is the top part, on the dorsal side. This is the part that you would see if you were standing above and looking directly down at one.
The plastron is the portion of the shell on the turtle’s belly, the ventral side.
These two sections are fused together on the side of the body in what is called the bridge. The bridge is a connecting section made from the same bony material as the rest of the shell.
Interestingly, if you look at their hip and shoulder girdles, they are actually inside of their ribcage! This would be like your arms and legs protruding from within your ribs.
What’s Inside
People are often curious about what exactly is underneath a turtle’s shell.
The answer is simple: organs.
All the vital organs are housed inside the turtle shell, except for the brain which resides in the head.
While it may seem like the head is underprotected, many turtles can retract their heads completely into their shell. This ensures the head is just as safe as the rest of their body when threatened.
Some aquatic turtles that can’t retract their head and limbs entirely within their shell can retract them partially.
Can Turtles Live Without Shells?
There is a simple answer to this question: no, they can’t!
A turtle without shell has no chance of survival.
If a turtle’s shell were to be removed, it would not be able to survive for any period of time. Turtles without shells die very quickly, as the shell is a vital part of their body.
Now that we know a turtle without a shell can’t live, let’s discuss six reasons why…
1. It’s Their Skeleton
A shell is much more than a simple covering, it is actually their skeleton! The shell itself is made up of their ribs, sternum and backbone that have fused together.
Turtles can’t remove their shells, just as you or I are unable to remove our backbone.
Shell anatomy is very different than that of any other vertebrate.
Their shell is connected to the rest of their body through blood vessels, nerves and connective tissue. The soft tissue and skin connects directly to the bone of the shell.
In attempting to remove the shell, you would need to sever a lot of very important tissues. If you were to successfully remove their shell, not only would you be taking away their backbone, but you would also be removing the spinal cord.
If the spinal cord were to be removed with its shell, the turtle would be unable to move.
It is not possible for a vertebrate to survive without a spinal cord.
This means that it is impossible for a turtle to survive without its shell.
2. It Helps Them Thermoregulate
A shell is very important when it comes to thermoregulation.
Turtles are a type of reptile and, so like lizards, they are unable to regulate their own body temperatures.
This means they rely on the environment to heat and cool their body. They mainly accomplish this by basking in the sun throughout the morning. They usually bask by laying on large rocks, logs or other surfaces outside of the water.
When it comes to basking, the more body surface area to soak up the sun, the better.
Turtle shells are the perfect surface to absorb heat from the sun. Their shell is usually darker on the backside and lighter on the underbelly.
This coloration helps camouflage aquatic species, but also helps with thermoregulation. Darker colors are known to absorb more heat than lighter colors. A darker carapace will help them absorb the most heat possible when basking.
3. Protection
One thing is clear when talking about a turtle’s shell, it is absolutely necessary for survival.
Some of the most important functions of their shell include protection and combat.
The hard shell helps them survive dangerous environments and more importantly, predators.
For Painted turtles, shells keep them well protected from a variety of threats such as otters, raccoons, minks, dogs, cats, foxes, bears and any other large predators.
Turtles and tortoises are generally known for being slow moving. This is mainly because their shells weigh them down. While this may seem like a disadvantage when encountering a predator, what they lack in speed, they make up for in armor.
When threatened, they can retreat either fully or partially into their shells, which makes it nearly impossible for predators to eat them.
Their shell is so good at protecting them that it can stop the bite of a crocodile.
There are very few animals that pose a threat to them.
Protection is a very important feature of their shell, but it may not have been the original function. Scientists now believe that shells may have originated as a digging tool in the early ancestors of turtles.
4. Combat
Turtles also use their shells for combat.
Some tortoises (which are technically turtles) use an extension of their shell called the gular horn to fight.
Both male and female species have a gular horn, though the males are usually much larger.
Males will frequently use their gular horn during breeding season to compete with other males and attempt to flip them on their backs.
Not only do modern species use their shells for combat, but there is evidence that this behavior was present in turtles nearly 23 million years ago. Prehistoric species like the Stupendemys geographicus used their thick, horned shell and shoulder pads in combat.
5. Camouflage
Not only can a shell help protect them from predators, it can also help them hide.
Lots of species of tortoises and turtles use their shells to help camouflage themselves.
For example, sea turtles often use their shell to help them blend in. The top part of their shell is often dark in color with various patterns which helps them blend in with the reef when looking at them from above. Their ventral side is usually very light in color which helps them blend in with the light water when viewed from below.
Many aquatic species have this patterning to help blend in with their watery environments.
Another example is Asian box species who also use a type of disruptive coloration on their shell to break up their body outlines and camouflage them into the environment. This type of camouflage helps them blend into very complex backgrounds.
There is some evidence that turtles can even change their shell color based on the substrate they are raised in.
If they are kept in a darker substrate, they will allocate more melanin pigment to their carapace which results in a darker dorsal side.
Their coloration can also vary based on gender, and is used to attract the opposite sex during mating season.
6. Nutrient Store
A shell is more than what it seems on the surface.
Their shell can also help with some complicated biological processes and is a nutrient store.
Calcium, sodium, magnesium, phosphates, carbon dioxide, fat, water and waste are just a few of the things that turtles frequently store within their shells.
Not only can they use these nutrients when in need, within their shells there is a structure that can store and release nutrients and chemicals.
For example, a shell can aid in lowering dangerously high levels of acidity in the blood. Lactic acid is accumulated in the blood through long periods of time with no oxygen. This process allows turtles to survive for much longer periods without oxygen than other reptile species.
Studies have been done on painted turtles which showed that through this process they were able to survive in 3°C water with no oxygen for 3 months!
Why They Need A Shell
A turtle’s shell serves as a shield for their soft inner body.
It encloses vital organs and ensures that they are well protected from the environment and any predators.
Protection is not the only function of a shell. It also helps them thermoregulate, store nutrients and even camouflage.
This means turtles have shells for multiple reasons:
- To protect from predators.
- Help them thermoregulate.
- Store nutrients.
- Camouflage into the environment.
The question of why turtles have a shell is straightforward, but how they came to evolve a shell is much more complicated. The evolution of their shell is highly debated, but there are a few common theories.
One theory is that the shell evolved through enlarged rib bones. This would mean that early species had rib bones that enlarged, combined with the vertebrae and sternum, and gradually evolved into the entire shell we know today.
Another theory is that the shell evolved from bony scales called osteoderms and that the carapace and plastron evolved separately.
Recently there have been turtle fossils discovered that have only the carapace or plastron.
This suggests the theory that they evolved separately may be true.
Regardless of the origin, the evolution of the shell was complete during the time of the dinosaurs in the late Triassic period with the first primitive turtle named Proganochelys. This species looked very similar to modern species and turtles have changed very little.
Can Turtles Get Out Of Their Shell?
It is a very common misconception that turtles can remove their shells.
This myth stems from many cartoons that have shown turtles taking off their shells. While this belief has been held by people for many years, this is simply not true.
There is no way a turtle will be able to get out of their shell.
A turtle’s shell is a part of their body and is actually their skeleton.
Turtles without shells do not live for very long.
Unfortunately, while a turtle’s shell is very sturdy, this doesn’t mean that they are completely safe as their shells can still be injured.
Missing shell pieces can occur due to an injury. While small pieces are usually inconsequential, missing larger pieces of the shell can be life threatening. You can often see older individuals with missing shell pieces that have occurred due to some injury and healed over.
Fractures on the other hand are usually a result of a fall from a large height or being stepped on.
Usually a fracture runs through a section of the carapace (the top of the shell). These injuries can be more severe and can even crush or destroy their spine.
Since a turtle shell is made of living bone just like our skeletons, it can heal.
Fractures will either heal naturally, or they can be bandaged by a vet until the bone heals together.
Specialist reptile vets usually use either bandages or plate implants to hold the different sections of the shell together during the healing process. This is similar to wearing a cast for a broken arm. This process will hold the bone together and allow for it to grow together and heal the fracture.
FAQs
What Does A Turtle Without A Shell Look Like?
It is not pleasant to imagine what a turtle without shell would look like, since the shell is made up of their skeleton. It would probably be similar to what you would look like without your backbone or ribcage! A turtle should not ever be removed from its shell as the result will be death. Removing their shell would require severing bone, nerves, blood vessels and connective tissue.
Are Turtles Born With Shells?
Yes, turtles are born with shells and will have them for their entire lives. The shell itself develops inside the egg and will be the size of a nickel for hatchlings. Turtles don’t shed their shells as they grow, instead the bone grows, just like our skeletons grow as we age. This means their shells will get bigger with them. However, as they grow shells will shed the outer layers of keratin resulting in a peeling appearance. This peeling is common and you can see it happening throughout the turtle’s life as they grow.
Are Turtles Attached To Their Shells?
A turtle is attached to its shell, just as you are attached to your ribcage. A turtle’s soft tissues and the underside of their shell are actually in direct contact. There are a lot of blood vessels, connective tissue, nerves and even skin connecting a turtle to its shell. This attachment ensures that the turtle is properly protected by its shell. This is one of the main reasons a turtle cannot survive without its shell.
Can Turtles Regrow Their Shells?
Turtles can regrow their shells, but with some limitations. Since a turtle shell is made of living bone, it can heal. They can regrow small pieces of their shell very slowly and heal fractures between two sections of shells, just like humans can regrow bone to heal a broken arm. However, they cannot regrow entire large sections of missing shell. This healing process happens very slowly and it will likely take a few years to completely heal even a small shell injury.
Summary
Turtle shells are a very interesting, complicated body part made from a series of bony plates called scutes. These scutes are covered in a hard horn-like material made of keratin.
A turtle’s shell is made up from their sternum, rib cage and vertebrae. It has two main parts which are called the carapace and the plastron.
Though it may be a common misconception, a turtle cannot be removed from its shell. Not only is a turtle’s shell part of its skeleton, its connected to its body through a variety of soft tissues.
The shell provides turtles with protection from predators, camouflage and even gives them a surface to help bask. It can also be used as a nutrient store and helps with a variety of different biological processes.
These important functions are just a few reasons why a turtle’s shell has made them such a successful group of reptiles for over 200 million years.
Their shell is absolutely necessary for survival.
A turtle can’t be physically removed from its shell and it can’t live without its shell either.
