Glaucus atlanticus: For once, the Internet is not lying to you

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!

Here's how the Smithsonian Magazine blog described the process last Spring:

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

A scientific paper documenting the presence of G. atlanticus in Andhra Pradesh.

The Sea Slug Forum has a description, photos, and sightings.

Image: Glaucus atlanticus © Taro Taylor, Creative Commons Attribution 2.0 Generic


    1. The first time I saw it, I thought that the Minbari delegate was about to dock.
      And did the person attached to the hand in the photo spend the last few years developing an immunity to nudibranch-borne nematocyst toxin?

      1.  If it’s captive, and didn’t consume any man o’ wars, then there isn’t any sting for it to have acquired.

    2. It still looks like a jrpg boss creature to me. Just a very, very tiny one. Or it’s being held by a giant.

    3.  The new look is okay, can we skip the thumbnailing of the images even after we’ve clicked on them? I’ve already seen a thumbnail in the post, clicking again seems redundant

    4. sorry for off-topic, but how come the pictures don’t open full sized like before? i have to click again on “original” and then it opens in a new tab.

      edit: obviously I need to RTFT before posting… sorry

  1. Wait till Jim Cameron sees this. He’ll cast a CGI animation of it as a lead character for one of the “Avatar” sequels.

  2. FYI, for those who are familiar with the impossibly lifelike Blaschka glass flowers at the Harvard Museum of Natural History: The Blaschkas did mollusks and cnidarians before they turned to flowers, and their Glaucus atlanticus is currently on display in the mollusk mini-exhibit. (In case you can’t see one in person.)

  3. I want a Ribofunk-style gene splice to replace my hair with pretty teal wavy man-o-war filled toxin tentacles from this guy.

  4. Nudibranches?  Why has no-one mentioned the sex life of Nudibranches! 
    In general Nudibranches are hermaphrodites, and they have a sharp, stinging penises. When two nudibranches meet they each try to sting and deposit sperm under their opponents skin without getting stung.  The sperm gets encapsulated but tries to migrate to the ovary to do some fertilization. Whoever gets fertilized has to go through the whole egg-developing process and that’s always so exhausting. I heard a lecture a few years back at Machine Project in LA by a hilarious marine biologist. He said  when he’s collecting specimens and puts a bunch of these together in a bucket, they go into a frenzy of stinging. They form a “fuck-ball,” he said, stinging and stinging and writhing around, and when they’re through they all  nap. 

  5.  Nudibranches are all by themselves a good reason to get SCUBA certified.  There are tons of different ones and they are awesome to look at.  Which brings me to…

    “don’t touch things that look pretty. Because they will probably kill you.”
    I got my SCUBA cert while living in Singapore and diving in Malaysia and Indonesia.  One of the first things I was taught is “Don’t mess with anything really pretty or really ugly because you will probably die.”

  6. Has a name like a comic book interstellar villain, looks like it should be miles across flying through space.

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