Sea pens are stunning eight-pointed corals. Colonies of some species of these polyps resemble bird feather.
A colony of these animals consists of a large main polyp that forms its fleshy trunk, and numerous small secondary polyps located on the top end or on special lateral outgrowths of the main. Most sea pen has an internal horn skeleton, impregnated with lime, and well-developed muscles, allowing the animal if necessary to arbitrarily bend in any direction. Unlike other colonial coelenterates animals, sea feathers are never attached to the substrate. Their lower free end is inserted into the soft ground. Therefore, although sea feathers are fixed and lifestyle, they can, if necessary, to move on the ground and re-grow in a new place.
Sea feathers feed mainly at night, and quietly rocking on his leg. As dusk animal begins to unfold, his body covered with lots of fluffy polyps, ready to absorb food particles, bring water.
Many sea pens have a unique ability to glow, emitting violet, blue-green or yellowish light. Some sea pens glow all departments of the colony, others only polyps or adjacent part of the trunk.