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Sea Pens are graceful creatures resembling a plump, old-fashioned quill pen. They are classified as colonial octocorals, and, unlike other octocorals, each Sea Pen is a colony of polyps, each with eight tentacles. They are supported by internal skeletal structures and have adapted to living as sessile animals partially embedded in fine sediments on the sea floor. They range in color from dark orange to yellow to white.
The primary polyp loses its tentacles and becomes the stalk of the Sea Pen with a bulb at the base. The secondary polyps form the branches of the Sea Pen. They are able to relocate and re-anchor themselves if need be. They feed on the plankton that goes by on the currents. As a defense against predators (like red stars), they force water out of themselves, deflating and retreating into their bulbous foot. If touched, they emit a bright greenish light.
Sources: NOAA, Monterey Bay Aquarium, Wikipedia.
This photo was taken with a Canon EOS 6D, EF24-105mm f/4L IS lens, 1/80 sec at f/5.6, ISO 10,000 captured on a Lexar 400x SDXC UHS-1 memory card