This Sea Creature Spends Most of Its Life Without a Brain

When we think about the brain, we usually picture the body’s ultimate control center. Without it, we cannot think, move, feel, plan, or survive. But deep underwater lives a tiny marine creature that does something almost unimaginable: once it settles down permanently, it begins digesting much of its own brain.

The creature is called a sea squirt, and despite its simple appearance, scientists consider it one of the strangest animals in the ocean.

A Tiny Swimmer With a Primitive Brain

At the beginning of its life, the sea squirt looks almost like a microscopic tadpole. During this stage, it swims freely through the ocean searching for a suitable place to settle permanently.

At this point, it actually possesses a simple nervous system and primitive structures somewhat similar to the early nervous systems found in vertebrates. It can move independently, navigate through water, and respond to its environment.

But then everything changes.

The Moment It “Eats” Its Brain

Once the sea squirt finds a stable surface, usually a rock or coral, it attaches itself permanently and stops moving through the ocean almost entirely.

And from that moment, its body makes an extraordinary decision.

Since it no longer needs to search for food, escape predators actively, or navigate through space, maintaining a more advanced nervous system becomes unnecessary from a biological standpoint.

So the sea squirt begins absorbing and breaking down large parts of its own nervous system, including the primitive brainlike structures it once relied on while swimming.

In simple terms, the animal essentially digests its own brain.

A Life of Almost Complete Simplicity

After settling down, the sea squirt lives an extremely passive existence.

It spends the rest of its life filtering seawater through its body and feeding on tiny drifting particles. There is almost no movement, no hunting, and no active decision making.

From a survival perspective, scientists believe the animal no longer needs the energy required to maintain a more complex nervous system.

Surprisingly Related to Humans

What makes sea squirts especially fascinating to researchers is that they are considered distant relatives of vertebrates, including humans.

Although adult sea squirts look incredibly simple, their early developmental stages contain primitive features connected to the evolutionary origins of vertebrate nervous systems.

In fact, scientists study sea squirts partly because they may provide clues about how more advanced nervous systems evolved over time.

One of Nature’s Strangest Transformations

The sea squirt remains one of the most unusual examples in nature of an animal radically transforming its own body after settling into adulthood.

While humans spend enormous effort protecting and developing the brain, this tiny marine creature reaches a point where biology decides the opposite:

If you no longer need it, why keep it?