THE BRAINS OF THE OPERATION
This is a sea squirt.
As creatures go, they’re among the most primitive and prehistoric: their fossil record stretches back more than half a billion years. They’re also in possession of one of the most extraordinary lifecycles of any animal on the planet.
You see, when a sea quirt hatches from its egg, it becomes—for a time, at least—a tadpole-like larva, capable of swimming about the open sea looking for the best place to anchor itself and begin feeding. These “squirtpoles” (not a technical term) are fully equipped with a spinal cord, a primitive eye, and a tail for mobility. But once they’ve swam about a bit and found a suitable anchor point, something very odd starts to happen.
First, the larva latches permanently on to its new home. Then, it sets about eating its own brain.
Why? Well, sea squirts only need a central nervous system (of the brain-and-a-spinal-cord kind) while they’re looking for their home. That means that once that operation is complete—like a British expat emigrating to sunny Spain—they will quite simply never move again.
That then makes a rudimentary brain designed for controlling motion utterly superfluous, and so the sea squirt takes it upon itself to absorb its own central nervous system.
And there it remains, in total ignorance of everything except taking in food and reproducing. Also like a British expat.