The Octocorallia include blue coral, soft corals, sea pens, and gorgonians (sea fans and sea whips).
These groups have polyps with 8-fold symmetry, each polyp having eight tentacles and eight mesenteries. Corals are sessile animals in the class Anthozoa and differ from most other cnidarians in not having a medusa stage in their life cycle. Most corals are colonial, the initial polyp budding to produce another and the colony gradually developing from this small start.
Polyps feed on a variety of small organisms, from microscopic zooplankton to small fish.
The Octocorallia appears to be monophyletic, and primitive members of this group may have been stolonate.Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in length.A set of tentacles surround a central mouth opening. Over many generations, the colony thus creates a large skeleton that is characteristic of the species.Corals are marine invertebrates in the class Anthozoa of phylum Cnidaria.They typically live in compact colonies of many identical individual polyps.Individual heads grow by asexual reproduction of polyps.