Tunicates
Here, the ink-spot ascidian is surrounded by translucent blue ascidians.
When threatened, the tunicate shrinks and closes its siphons.
Clavelinas are small ascidians with transparent bodies living in colonies.
This is a colonial ascidian. The points that cover the body are the inhalant orifices of the members of the colony who share one or more exhalant siphons.
An othe form of colony
The name tunicates comes from the integument that protects their body, called the tunic. They are filter feeders that feed on plankton.
There are several classes: pelagic tunicates like salps, and tunicates like ascidians. I only show pictures of ascidians.
Tunicates go through a larval stage. Their larva looks like a tadpole and its tail has an axis called a rope, a prefiguration of the spinal column of vertebrates. In fact, despite the apparent simplicity of these animals, we are close relatives!
The solitary adult ascidians look like a bag with two siphons to allow the circulation of water. Colonial ascidians group multiple individuals within a single tunic.
The ink-spot sea-squirt is a beautiful solitary ascidian that can reach six inches. Inhalant and exhalant siphons are perfectly visible.