#5273 – Sea Pen
2018 50c Bioluminescent Life
Value: 50¢ 1-ounce first-class letter rate- Forever
Issued: February 22, 2018
First Day City: Fort Pierce, FL
Type of Stamp: Commemorative
Printed by: Banknote Corporation of America
Format: Pane of 20
Quantity Printed: 40,000,000 stamps
All over the globe, feathery sea pens can be found anchored into the ocean floor. In some instances, a startled sea pen will light up the darkness to ward off a predator.
A type of colonial soft coral, sea pens get their name from some species’ long, spindly polyps that resemble antique quill pens. However, of the 450 described species (about 200 of which are recognized), few have this appearance. Other types of sea pens look more like clubs or fluffy wires. Sea pens root themselves into the ground and catch plankton in their polyps, allowing the current to bring their food to them. If necessary, they can uproot themselves and move to another spot.
If sea pens are threatened, they can shoot water out of their bodies to retreat into their stalks. Or, if they are one of the 20 bioluminescent species, they have another option. When another creature touches them, they emit a bright green or greenish-blue light from their stalk, with a blue light at the tip. Some have also been found to emit a pale lilac light, which is rare. This lighting effect is likely used to ward off predators or attract the attention of larger creatures to eat their attackers.
Sea pens can produce a brighter light when touched by a predator and weaker light when touched by a non-predator, possibly so they don’t attract a larger creature if they know they are not in danger.