They actually squirt when you squeeze them, as their name implies. And they are more closely related to humans than many animals that live in the ocean. Sea squirts are these strange, glassy little sacs that somewhere in their tiny soft bodies have a kind of a simple dorsal nerve or chord.
In humans, that dorsal nerve evolved to have a spinal column to protect it that is composed of vertebrae. That makes us vertebrates.
I was recently reintroduced to these slimy relatives on some washed up fishing gear appeared after the recent tropical storm. They form a jelly-like coating on surfaces that at first look slimy and not very interesting. But, as with many seemingly simple animals, when you look more closely, they are quite complicated and beautiful. The bottom of the vase is attached to something hard โ a rock, a dock, a rope, for example. The top of a sea squirt is actually more like a double vase โ one takes water in and one squirts it back out as they filter out tiny plankton form the water.
This is a lot like clams that have intake and outtake siphons. While they are individually lovely creatures, en mass they can be problematic. Instead, they form colonies. They do this either by budding off little parts of their bodies into new baby squirts or by releasing larvae into the water that then settles into new spots. These colonies can get quite large and cover big portions of surfaces, weighing them down and clogging up openings.
This is not very convenient for fishermen or others keeping gear in the water. As with many species that cause problems in Maine waters, sea squirts are not native to Maine. They likely arrived in the ballast water of ships coming from places far away sometime in the early s.
