Pennatulidae

Pennatulidae is a family of marine invertebrates belonging to the order Pennatulacea, commonly known as sea pens. These colonial animals are found in oceans worldwide, inhabiting soft-bottom substrates from shallow waters to the deep sea. Sea pens are characterized by their feather-like or quill-like appearance, which gives them their common name. The colony is anchored to the seabed by a peduncle, a root-like structure. The upper part of the colony, called the rachis, bears numerous polyps. These polyps are specialized for different functions, including feeding, reproduction, and defense. The feeding polyps, known as autozooids, capture plankton and other small organic particles from the water column using their tentacles. Reproductive polyps, or gonozooids, are responsible for producing gametes. Some species also possess protective polyps called siphonozooids, which help in water circulation. Pennatulidae exhibit a wide range of colors, often vibrant reds, oranges, and purples, and can vary significantly in size, with some species reaching over a meter in length. They are sessile organisms, meaning they remain in one place once settled. Their bioluminescence is a notable feature in some species, producing light in response to disturbance.