A sea pen is a colony of polyps living together. The primary polyp has no tentacles and is the stalk of the pen. The secondary polyps live attached to the primary one, and catch plankton with their tentacles.
A sea pen is a colony of polyps living together. The primary polyp has no tentacles and is the stalk of the pen. The secondary polyps live attached to the primary one, and catch plankton with their tentacles.