How do cnidarian colonies form?

Cnidarian colonies form through asexual reproduction, a process in which new individuals are created by budding off tissue from a parent or by the parent dividing into smaller individuals.1

When these polyps remain physically attached to one another or stay embedded within a common mass of tissue, they constitute a colony. In many of these colonial structures, the polyps share a common coelenteron, allowing food captured by any individual member to be distributed throughout the entire colony.1

Depending on the species, these colonies may be supported by various skeletal structures. For example, many hydroid polyps secrete a horny, chitinous external skeleton that encases the polyp and the network of stolons connecting the colony members. Other colonies, such as those of anthozoan corals, may form massive or branching skeletons composed of calcium carbonate, while others utilize internal proteinaceous rods or microscopic spicules for support.2