Pyrosomes

So I ran across these crazy animals called pyrosomes a while back and I have been completely fascinated by them. When I was first presented with them, I could not figure out what they were! It turns out that they are a type of tunicate... and indeed looking at them under a microscope does help point that out.


Here you can see an individual of the tunicate colony, making a u shape, and surrounded by a clear tunic. The left side of the U is most likely the endostyle, a structure which gives support. On the right side of the U, the thicker side, is the pharynx, which they use to filter their food. Below that, the thick, pinkish structure is most likely the gut.

Each of those pyrosome colonies were made up of hundreds of these individual zooids, each of which captured its own food by filtering water through its pharynx. However unlike regular tunicate colonies, where the filtered water comes out somewhere along the surface of the colony, in pyrosomes (which are shaped like a cone with the smaller end closed off) the filtered water is shuttled to the inside and then comes out the large end. This allows them to swim!

It's hard to imagine these very dense, hard colonies swimming, but that's just what they do. Additionally, their name (pyrosomes = fire body) comes from one other unique feature that they possess. At the tip of each of the zooids they have a light producing organ, which allows the colony to light up like a christmas tree. I would love to see one drifting along, shining gently in the dark sea...