Sea squirts don’t even look like animals, but we all had a common ancestor hundreds of millions of years ago. When their eggs hatch they look a little like tiny fish. It was animals like these that were the ancestors of all animals with backbones.
The tiny fish-shaped young sea squirts can swim and find a solid place like a rock to attach themselves.
Their body then goes through a remarkable change. They grow into almost a ball shape with an inlet and outlet siphon for water. They filter food from the water and can pump a litre of seawater in an hour. When they are bumped they squirt the water out of their body.
For protection they are able to make a thick, tough coat around their body from something similar to cellulose that is made by plants. This brown cellulose- like coat makes the sea squirt look and feel very leathery.