This is actually a real life animal.
I know. I didn't believe it either. When it turned up in my Facebook feed, via my Aunt Beth, I assumed that this had to be a hoax photo. Had to be. I mean, just look at it. This animal looks like it should appear in pretty photos forwarded to you by your aunt that later turn out to be the result of a photoshopping contest on Something Awful, right?
But then it was on Wikipedia, too. And I thought, "Okay, it's still the Internet. Somebody is clearly just getting really elaborate in their trolling."
And I suppose that's true. If by "somebody", what I mean to say is "natural selection".
This is the Glaucus atlanticus. It is a type of nudibranch—shell-less mollusks known for their extravagant shapes and colors. It is venomous. And I am now almost completely convinced that it's not a joke.
The London Natural History Museum has some good information about these creatures, including the drawing at left, which was made in the late 1700s by Sydney Parkinson, the official ship's illustrator for Captain Cook's second voyage to the Pacific.
You see all those pointy bits Glaucus atlanticus? According to the Natural History Museum, those are called cerata. They are the organs where G. atlanticus stores the stinging cells that it steals from the jellyfish it eats.
Because it eats jellyfish. And not just any jellyfish—but Portuguese Man o' War jellyfish. G. atlanticus eats the jellyfish tentacles and, as part of the process of digestion, stores stinging cells from those tentacles in the tips of its cerata. Then G. atlanticus gets to be venomous, too. Fun! Sharing!
A gas-filled sac in the stomach allows the small slug to float, and a muscular foot structure is used to cling to the surface. Then, if it floats by a man o' war or other cnidarian, the blue dragon locks onto the larger creature's tentacles and consumes the toxic nematocyst cells that the man o' war uses to immobilize fish.
The slug is immune to the toxins and collects them in special sacs within the cerata—the finger-like branches at the end of its appendages—to deploy later on. Because the man o' war's venom is concentrated in the tiny fingers, blue dragons can actually have more powerful stings than the much larger creatures from which they took the poisons.
In conclusion, there are two lessons to take away from G. atlanticus.
First, the Internet isn't always lying to you. Just sometimes.
Second, don't touch things that look pretty. Because they will probably kill you.
More at The Encyclopedia of Life
Image: Glaucus atlanticus © Taro Taylor, Creative Commons Attribution 2.0 Generic