What the sea squirt tells us about our brain

Recently I came across a really interesting fact about the common seasquirt. This peculiar creature lives its life in two very different phases.


an “adult” sea squirt

A day in life of a seasquirt

When it’s born, it quickly develops from egg into a tadpole-like creature. It has a simple eye and a tail to swim about. It even has a spinal cord and a primitive brain to control it’s movement.

The seasquirt swims with a purpose: it is looking for a home where it will spend the rest of its life. So, when it finally finds a rock (or boat) that it likes, it latches on to it and the second phase of its life begins.

seasquirt metamorphosis

metamorphosis of the sea squirt

Here’s where things get really interesting. Once it has found a home, the seasquirt starts eating its own brain1. Being permanently attached to a home makes the need for a brain superfluous, so its body digests it for the protein that it provides and then keeps on living for decades without a brain.

What this means for us

The seasquirt, a distant relative to humans, gives us some insight about what the brain evolved to do: its original funciton is strictly related to movement.

In fact, recent studies suggest that physical activity increases the white matter microstructure in our brain23. This white matter is responsible for fast and efficient communication between different brain regions.

white matter

white matter structure of human brain (MRI)

Let’s pause and think about this for a moment. In modern society, children and adults are more and more encouraged to spend big part of their day sitting at a desk. And when we have free time at the end of the day we often find ourselves captured by a screen. These stationary behaviours have a negative effect on our brain development3, so we should actively try to avoid them.

Adjustable-height desks are a very productive solution to the work-related problems, but not all can afford that. Ideally one should try and be more active. Even something as simple as setting up a reminder to stand up and walk about every so often can make a difference. In fact, that’s what I’m about to do, together with abruptly ending this blog post.

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