Spirula is a bizarre creature that might seem more like a sci-fi alien than something swimming around in our own oceans. For one, this strange little, squid-like animal has a spiral shaped shell inside it’s body. Instead of using the shell for protection like its cousin the snail, Spirula pumps air into the empty chambers to control its own buoyancy. During the day, it sinks down into the darker deep waters, probably to avoid predators. Not only is the water dark enough to hide, but without photosynthesizers, those deep waters also lack the oxygen concentration that many predators need to swim fast, but Spirula has its own built-in SCUBA tank to make it through the dangerous daytime hours, hiding in the shadows beneath the sunlit zone.
The anatomical anomalies of Spirula aren’t limited to its spiral shell, it also has a light on top of its head. It glows a steady green for hours at a time. Unlike other bioluminescent animals who shine their light downward to mask their silhouette from predators below, and unlike predators like the angler fish who use their light as a lure, Spirula doesn’t seem to use its light for anything relating to getting a meal or avoiding becoming a meal. Perhaps it’s just shining a friendly ‘hello’ to other Spirula in the neighborhood. Use a bottle of Spirula Green ink to write a letter to one of your neighbors, tell them ‘hello’ and tell them all about this strange animal with a green light on its head.