Facts: The Orange Sea Pen

Orange sea pens are octocorals that can be found in the temperate waters of the northeastern Pacific Ocean from the Gulf of Alaska to southern California. They are primarily associated with deeper water, though they may inhabit the sandy or muddy sea floor from near the surface to about 1,000 feet deep. Orange sea pens often occur in dense numbers. Their body color ranges from a pale cream to deep orange-red and consists of a central stem with branches on either side. Each adult sea pen consists of a colony of polyps working together for the survival of the whole. A sea pen starts off as one primary polyp that grows and expands to form the base and the central stalk. The base is what anchors the sea pen into the sediment. As the sea pen grows, it adds more polyps that have different jobs depending on their location within the colony. The feeding polyps are found along the branches. The pumping polyps are found near the stem. Each feeding polyp has eight tentacles armed with stinging cells surrounding a central mouth. The feeding polyps catch tiny drifting plankton. Sea pens face toward the current in order to maximize the flow of plankton over the feeding polyps. The feeding polyps are also responsible for reproduction. The pumping polyps take in or expel water, allowing the colony to inflate or deflate. Sea pens have an intricate system of channels that allow the movement of water and nutrients throughout their body. Fully expanded, large adults may extend for about two feet out of the sediment. Orange sea pens generally reproduce between March and April. A large, mature female can produce upwards of 200,000 eggs that are released and fertilized in the water column. The eggs drift along until they hatch into larvae. Larvae eventually settle onto the seafloor. A set of larvae becomes a tiny polyp. Orange sea pens can be long-lived, but they are often subject to predation early in life. They are consumed by many species of sea slugs and sea stars. When orange sea pens are physically disturbed, they can bioluminesce, producing a greenish-blue light that runs up and down the stalk and startles predators. They also produce a mild toxin. Additionally, sea pens can deflate by retracting their branches into their base to hide from predators. Sea pens can even relocate and re-anchor themselves if necessary. They can inflate with water and drift along with the currents in order to quickly relocate further away. For more marine facts, click the SUBSCRIBE button!!