The two atrial openings are the typical identifying characteristic of tunicates. Water is sucked in from one opening, passed through holes to the atrium, and discarded through the other opening, along with waste products from the intestinal tract. Mucus traps microscopic food particles for digestion. Their circulatory system consists of a muscular vessel and two opposing pace-makers that cause occasional irregular beats and a reversal in blood flow. In some tunicates, the atrium is also used to brood their young.
Social tunicates can reproduce asexualy, with runner-like arms that develop new individuals.
Depending on the type, they may or may not remain connected. Didemnum and Tridemnom are compound tunicates. They form crusts of the fused individuals. The individuals have separate incoming openings, but sometimes a common atrial chamber and opening are formed. Send me email.