The Blue Sea Dragon,
also known as Blue Angel, Sea Swallow, or Blue Sea Slug
Sometimes the photo of a stunningly bizarre creature can send me down a rabbit hole of further and further exploration. This just happened when I saw an image of a Glaucus Atlanticus, and I want you to join me on this journey of discovery. The creature doesn’t just look weird, but decidedly is. Barely more than one inch long, it is a gastropod, like the slugs and snails that eat the lettuce- or spinach plants in your garden. Living in the sea, it has lost its shell and belongs to a group of soft-bodied marine sea slugs called nudibranchs – talk about a curious bunch! I’ll get back to them a bit later, first some facts about the peculiar sea dragon.
It floats in the ocean upside down, below the surface, using a camouflage technique known as countershading: the blue side faces up, and for predators from above its body blends in with the blue of the ocean. Its silver/grey side faces downwards, merging it with the water’s bright surface when seen from below.
Besides being able to hide in plain sight, the blue dragon has another effective defense mechanism: it has a painful sting with enough venom to seriously injure a perceived enemy. The strange thing though is that the blue dragon doesn’t produce the venom on its own. It feeds on another extraordinary creature, the Portuguese man o'war – which looks like a jellyfish but actually is a species of siphonophorae, which means that it is not one, but a group of animals, a colonial organism. Each one of its genetically identical individuals called zooids or zoöids has a particular function, but they all work together as one. See how fascinatingly peculiar this gets?
The man-of-war has long, thin tendrils that grow to 30 feet on average but can reach up to 100 feet. These tentacles are covered with tiny capsules (nematocysts) which are filled with venom used to paralyze and kill fish and other small creatures. Humans beware – a sting is awfully painful and causes welts on exposed skin.
Getting back to the sea dragon: the tiny creature feeds on the much bigger man-of-war and stores the stinging nematocysts, even further concentrating the venom. This is how it can produce a deadly sting without being venomous on its own. Actually, its venom will remain active even after a blue dragon dies. Better not to touch, should you find one on a beach! It can kill a human being, and anybody who got stung should seek out a hospital to get treated.
Often, several sea dragons band together and form what is called a blue fleet. That way, they can easily nibble on the big Portuguese man o’war. From what I can gather, they don’t kill their prey, only take chunks which possibly grow back? I couldn’t figure that out.
Besides the Portuguese man o'war which is their favorite food, sea dragons also snack on other siphonophores (remember, these are colonial animals functioning as a single organism). Preferred creatures are the By-the-wind sailor (Velella ), the blue button (Porpita porpita), and the violet sea snail (Janthina janthina), also called purple storm snail. And if they don’t find any food and are really hungry, sea dragons are known to eat each other…
And here is another interesting fact about sea dragons: they are hermaphrodites, which means that each individual produces its own sperm and eggs. Nevertheless, each sea dragon still has to mate with another of its kind, which has to happen in a very careful manner, so that they don’t sting each other! Each slug then produces a string of about 20 eggs which it attaches to floating objects such as driftwood.
The blue sea dragon isn’t the only stunningly beautiful sea slug, or nudibranch (for a spectacular set of photographs, please visit this Smithsonian webpage). One particularly fascinating member of this group is the Sea Bunny (Jorunna parva), less than one inch long! What looks like fluffy, fuzzy fur are fleshy protuberances, tiny rods used for sensory functions. Some of them have black nobs at the end which gives the sea bunny its spotted look. What looks like bunny ears are two rhinophores; scent or taste receptors which help the sea bunny to find food and also potential mates. Like the sea dragons, they are hermaphrodites, and they also feed on venomous creatures, absorb the toxic chemicals, and use them to defend themselves against potential predators. As cute as they look, they’re definitely not cuddly.
It’s quite humbling, isn’t it, when one considers that all these countless, seemingly strange creatures co-exist with us. And if they’re lucky, they’ll neve encounter a human being. Their lives may be short, sea bunnies live for one year at most, but that’s all relative. Compared to some several-thousand- years old trees human lives are but a short moment. Maybe all life on earth is one big colonial organism, a siphonophore. We just haven’t learned yet how to work together as one…
the pics are very cool!
re: gaia theory. maybe not just life ON earth, but the earth from core to thermosphere.