Say what you will, but jellyfish, a.k.a ‘jellies’ a.k.a. ‘true jellies’ a.k.a. ‘medusae from the phylum Cnidaria’ (trans. ‘jellyfishes’) have done quite well for themselves in spite of their obvious limitation of lacking any brains.

This is not to be confused with the colloquial expression ‘he/she has no brains’ – meaning that he/she has a physical brain present, yet said brain is a Raiders fan, or said brain is sure it found a system for winning at Keno, or said brain got kinda drunk and argued somewhat convincingly to itself that it was okay to eat a bacon-wrapped hot dog from a street vendor in Tijuana1.

Rather, jellyfish literally have no brains. At all.

‘Hey, I just had an idea. Wait…no…it’s gone.’

Yet succeed they have. Comprised of about 95% water (and 0% brain) jellyfish can be found in stable populations throughout the world’s oceans, from top to bottom and also in freshwater. And there are at least 2,000 different species.  And they accomplished all of this without the benefit of an iPad. Impressive.

Not only have they traveled the world and done fairly well despite their brainlessness, jellyfish also manage to kill and devour their prey and deter predators.  Now, one probably wouldn’t be very afraid of a shark that didn’t have a brain. Or a snake without a brain. Or a bear. Indeed, it might be entirely hilarious if a brainless bear was trying to attack you. There’d surely be a website called and it would be ‘dedicated to providing the most recent videos of brainless bears trying to do things.’ But yet we all intuitively sense that a jellyfish – even a brainless one – is a different matter altogether. And that intuition turns out to be completely correct.

One of the hallmark features of Cnidarians (and therefore jellyfish) are tiny organelles called nematocysts, which are specialized stinging apparatuses that have been described as miniature ‘cocked guns.’ Embedded in the tentacles (and requiring much less maintenance in salt water than actual cocked guns), nematocysts contain tiny, coiled, often-barbed, poisonous threads that plunge venom into the skin of anything unfortunate enough to brush up against a jellyfish. This effectively paralyzes small prey and has ruined many an impromptu skinny dipping session.

Now I remember. I was going to kill you and eat you. I knew it started with a K.’

Perhaps not so surprising for an animal lacking a brain, the jellyfish developed only one gastrovascular opening for both the mouth and the anus2. Known in the jellyfish community as ‘The Great Mistake,’ the mouth/anus serves to devour plankton, fish, crabs, barnacles and sometimes other jellyfish. And then to poop same meals back out later. Adorable.

The Great Mistake aside, jellyfish reveal one of nature’s nasty little paradoxes: Successful evolving – being the fittest and thus ‘the best’ and going on to make a decent living – does not require a brain. However you turn that over in your massive neural network, it surely must diminish the relative standing of humans in nature. And then when we consider that some people (with brains) on our planet actually consider jellyfish a delicacy (even after being informed that there’s no jelly in them), it only takes us and our giant brains down several more pegs. Which is certainly not anything we look for, but something that still has the benefit of reminding us not to spend so much time wondering 24/7 how we’re doing vis-à-vis everyone else, what it all means, what should we really be doing with our lives, is now a good time to buy a condo, et cetera.

Thanks, jellyfish.

Grade: C-

1 Or said brain works in the local coffee shop and when an Animal Reviewer ordered a ‘half decaf,’ said brain asked the Animal Reviewer what he wanted as the other half.

2 This is why the curriculums of jellyfish dentistry schools are virtually identical to those of their proctology programs. Same book and everything.

22 responses to “Jellyfish

  1. You’re killing me! This blog will kill me! =))=))

  2. Jellyfish are the light shows you don’t want to touch. The deep sea variety, anyway.

  3. Added bonus of jellyfish: one can encourage younger siblings to touch them while swimming. Not that I would support this sort of behavior or have ever engaged in it myself…

  4. I think consideration needs to be given to the jellfishes propensity for causing individuals to voluntarily get “peed” upon.
    Sure, plenty of animals can scare the piss out of you, but how many can make you say “dammit, now I gotta pee on my leg.”
    Whether this is cause to increase or decrease the grade is better left to the experts.

  5. What about the fact that there is a species of jellyfish that are immortal? I think we need to take that in to consideration while grading it.

  6. If you’re scuba diving, you can touch one side of them and push them around. And also you can use your bubbles to send them careening towards the surface. This is very entertaining, and not cruel, because they really don’t know the difference.

  7. To be fair to jellyfish:

    a) They taste delicious, especially with pesto
    b) They are a sustainable, environmentally friendly form of food
    c) They are 100% protein which means they are good for you too.

    They should be upgraded to AT LEAST a B for those reasons alone. 🙂

  8. Brandon M. Sergent

    The box jelly is the most invariably lethal organism on the planet. If the Great white gets an A+ so should the jelly.

    Of course having no brain, perhaps it won’t notice the insult.

  9. The immortal factor does not seem to be taken into account…

    Plus the fact that some species are as large as refridgerators.

    Extra Credit?

  10. No wonder jellyfish are so skinny… everything they eat (literally) tastes like s-it!

  11. @Rachel: 100% protein of a creature made up of 95% water makes them only capable of being 5% protein. If you’re looking for protein, you should try cattle; I hear they’re delicious and they don’t sting you when you push them into a meat grinder.

  12. But ah, what about the immortal ones? Aren’t they pretty awesome?? more than a C- I think.

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  14. i’m with carmen, that one of them has achieved biological immortality demands that grade get bumped up a full letter grade. minimum.

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  16. How have you not reviewed Brett Favre yet? He’s obviously not human!

  17. Jellyfish…hmmm….another one of the creatures that man can’t understand….I like rice.

  18. I think you’d do well to take whales down a notch. Being the biggest animal in the ocean is like being the biggest dust particle in Texas Stadium, not so impressive in the proper context.

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  20. “Perhaps not so surprising for an animal lacking a brain, the jellyfish developed only one gastrovascular opening for both the mouth and the anus2. Known in the jellyfish community as ‘The Great Mistake,’ the mouth/anus serves to devour plankton, fish, crabs, barnacles and sometimes other jellyfish. And then to poop same meals back out later. Adorable.”

    On the bright side, this led to a great “You Don’t Know Jack” trivia question, with the immortal follow-up joke: “This plankton tastes like crap.”

  21. apply for VA loan

    What we eat is what we are. Somebody once tol me that. Hmmmmmm

  22. Seen your webblog via bing the other day and absolutely like it. Keep up the great work.

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