The Glaucus atlanticus, commonly known as the blue dragon, sea swallow, or blue angel, is a captivating sea slug that enchants and warns with its vibrant colors. This tiny marine creature, belonging to the nudibranch family, floats upside-down on the surface of tropical and temperate oceans worldwide, including the Atlantic, Pacific, and Indian Oceans.
Appearance and Camouflage
Measuring up to about 3 cm in length, the blue dragon displays an exquisite pattern of countershading. Its bright blue underside, which faces the sky, blends seamlessly with the ocean’s surface, camouflaging it from predators above. Conversely, the silver-grey dorsal side, which faces the ocean depths, reflects the light from below, making it almost invisible to predators from beneath. This dual-toned camouflage not only protects it from aerial attacks but also from predators lurking in the water.
Unique Lifestyle
Glaucus atlanticus spends its life passively floating on the ocean’s surface, buoyed by air it ingests which forms a bubble in its stomach. This lifestyle is both serene and perilous, as the sea slug is entirely at the mercy of ocean currents and winds, occasionally washing up on beaches where it can be observed by the curious.
Diet and Defense
The blue dragon is a carnivorous predator, feasting on other pelagic creatures, most notably the venomous Portuguese man o’ war. It’s here where the Glaucus atlanticus reveals its most extraordinary trait: it can ingest and store the nematocysts (stinging cells) from its prey. These nematocysts are then concentrated within the tips of its cerata (finger-like appendages), turning the blue dragon into a walking weapon. The sting of a Glaucus atlanticus can be more potent than its prey, capable of causing significant pain, swelling, and even allergic reactions in humans.
Reproduction and Distribution
As hermaphrodites, blue dragons possess both male and female reproductive organs. However, they still require a mate to reproduce, laying strings of eggs on floating debris or the remains of their prey. Their distribution spans across the warm waters of the globe, though they are expanding into new areas, likely influenced by changing ocean temperatures and currents.
Encounters with Humans
While Glaucus atlanticus is a sight to behold, if you come across one of these little creatures, you probably shouldn’t pick it up. Their deceptive beauty hides a powerful sting.
