The Sea Creature That Turns Inside Out to Eat

At first glance, it looks like a slow-moving star lying flat on the ocean floor. Harmless, quiet, and peaceful. But wait a moment—because when it finds its next meal, something truly bizarre happens.

This creature doesn’t bite. It doesn’t suck or swallow like most predators.

Instead, it turns its stomach inside out, pushes it through its own mouth, and digests its food outside its body.

Meet the starfish—or more accurately, the sea star. One of the strangest eaters in the entire animal kingdom.

Not Really a Fish

Let’s start with a small clarification: starfish aren’t actually fish. Scientists prefer the term “sea stars” because these creatures have no bones, no blood, and no brain—all features that traditional fish have.

They belong to a group called echinoderms, which also includes sea urchins and sea cucumbers. But among this strange family, sea stars might be the weirdest.

And their method of eating is what sets them apart from almost every other animal on Earth.

A Mouth with a Twist

If you’ve ever picked up a sea star at the beach or in a tide pool, you might’ve noticed a small hole in the center of its underside. That’s its mouth.

But the sea star’s mouth doesn’t work like yours or mine. It doesn’t chew. It doesn’t swallow. It doesn’t even open wide.

Instead, when it finds prey—usually a clam or mussel—it does something almost no other animal can do: it pushes its stomach out through its mouth.

Yes, you read that right. The stomach comes out of the body, wraps around the food, and digests it externally.

Only after the meal is broken down into a mushy soup does the sea star pull its stomach back into its body—along with the digested nutrients.

It’s like turning a glove inside out, wrapping it around your lunch, and then pulling it back in once it’s all melted.

Breaking Through Armor

You might wonder: why go through all that trouble?

Because sea stars often eat shelled animals like mussels and clams—creatures with hard exteriors that most predators can’t access.

Sea stars solve this problem with brute strength and patience. Using hundreds of tiny tube feet, they grip both sides of a mussel shell and slowly pull. It can take hours.

Eventually, the shell tires and opens just slightly. And that’s all the sea star needs.

It slips its stomach inside the tiny opening and begins digesting the animal while it’s still in the shell.

It’s a slow-motion ambush that ends with an entire mussel being turned into soup—outside of the sea star’s body.

Two Stomachs, No Problem

Sea stars actually have two stomachs: the cardiac stomach and the pyloric stomach.

The cardiac stomach is the one that gets pushed out to do the external digestion. Once the food is liquified, it’s pulled back in, where the pyloric stomach finishes the job.

This two-step system is incredibly efficient—especially for an animal with no brain and no eyes (only basic light sensors).

And it’s not just efficient—it’s ancient. Sea stars have been using this method for over 450 million years.

No Blood, No Bones, No Limits

Sea stars don’t have blood. Instead, they use seawater to transport nutrients throughout their body via a system of canals. Their tube feet also run on water pressure, allowing them to move silently across the seafloor like a ghost.

They also don’t have a centralized brain. Yet, they show surprisingly complex behaviors—such as problem-solving and directional movement based on light and touch.

Despite their soft appearance, some species can regrow lost arms, or even an entire new body from a single severed limb.

They’re built for survival—and their bizarre eating habits are just one part of a much stranger design.

When the Predator Looks Harmless

You’d never guess that this slow, pretty sea star is a deadly predator. But nature loves to surprise us.

Its way of eating—turning its stomach inside out and digesting prey alive—is like something out of a science fiction novel. But it’s real. And it happens every day, silently beneath the waves.

The next time you see a sea star on the beach, remember: behind that calm, peaceful shape is one of the weirdest and most effective hunters the ocean has ever known.

It may look like a star. But it eats like a monster.