Henry Gee

These are the sea squirts, my apologies.

But some of the sea squirts live in one place.

Some of them float around in huge colonies in the sea.

There are some called pyrosomes that have these huge colonies that are kind of trumpet-shaped.

I mean, and divers can swim inside them.

So they emerged at the time of the Cambrian explosion and they're still visible today.

Yes, there are fossil tunicates from the Cambrian explosion.

But some of the tunicates have evolved to be really, really strange.

I mean, there are these tiny ones called larvaceans.

which are still tiny, the size of a grain of rice, and they are still divided like a tadpole into a switchy tail and a head, and they filter feed from the sea.

But to do this, they secrete this enormous mucus structure called a house, which is unbelievably intricate, and it's made out of mucus that they secrete in huge amounts using genes and proteins that are seen nowhere else in nature.

And they use these for a few hours and then shed the lot and grow another one.

And these creatures have a life cycle of a day, a week or so.

And these mucus houses drift to the bottom of the sea and they are a major, major part of the carbon cycle.

of the earth.

And yet not many people know about these because all this happens way, way out in the open sea.

And these things are very fragile.

So most of these tiny tunicates, they're the size of a grain of rice and their house is the size of a walnut.

But there are ones that are maybe fossils that are known where they were fairly big animals and the house was the size of a football.

And you can imagine shoals of these.