Marine Wildlife Encyclopedia
Colonial Sea Squirt Didemnum molle
Although it appears to be solitary, the colonial sea squirt lives in urn-shaped colonies that share a single exhalent siphon (an opening through which water exits). The colony is dotted all over with the inhalent, or ingoing, siphons of the tiny zooids—the individuals that make up the colony. The colonial sea squirt’s green color results from the presence of the symbiotic cyanobacterium Prochloron.