Sea pens are so named because of their feather-like bodies that resemble quill pens, which were used as a primary writing tool until the invention and popularization of the metal pen in the early 19th century. The sea pen is a cnidarian, which also includes corals, jellyfish, and anemones. It is a colonial animal, featuring many polyps that all perform a specific function in its maturation. A single polyp forms the “stalk” of the animal, which acts as a root for the entire column, while others branch out to form separate groups that manage water intake, feeding, and reproduction.
While the sea pen will generally remain rooted in one place, they are capable of relocation if food is scarce, or threatened by predators. Sea pens ingest their food floating in the water column, so they will position themselves where currents provide a steady stream of plankton. Moving becomes necessary due to the increased presence of nudibranchs and sea stars, the sea pen’s natural predators. They spawn similarly to corals, by a timed release of eggs and sperm into the water column, and fertilized eggs become larvae that drift for a time before they settle into the sea floor to begin their life cycle. Research on sea pens suggests that they may live up to 100 years!
