The 60 foot long jet powered animal you’ve probably never heard of

Screen cap one of the only pyrosome videos out there. Full video at the end of this post.
Screen cap from one of the only pyrosome videos out there (see the end of this post).

I was living in Africa the first time I saw a pyrosome, and I nearly cried. I was doing research on plankton, which meant long days staring down a microscope plucking through tiny dead things. And then there it was. I actually gasped in recognition. My first real life pyrosome. Among many marine-inclined folks such as moi, pyrosomes are like unicorns. Completely improbable, utterly mysterious. And why?

For starters: if the Borg and the Clone Wars had a baby it would be a pyrosome. One long pyrosomes is actually a collection of thousands of clones, with each individual capable of copying itself and adding to the colony. And like members of the Borg, which are  mentally connected, pyrosome members are physically connected– actually sharing tissues. And while the Borg live in a big scary ship, pyrosomes are the big scary ship. The whole colony is shaped like a giant thimble with a point on one end and an opening on the other, and in some species this opening can be up to 6 feed (2 meters) wide– large enough to fit a full grown human inside [1]. Under normal circumstances, this sort of thing would scare the crap out of me.

But the pyrosome I found was cute. No larger than a jellybean. As I looked closer, I realized I could see right through it. Right into the guts. Each little “wire basket” is the stomach of one member of the colony. They take water in through a mouth on the outside of their space-ship body, pass it through the little basket to filter out the nom bits, and squirt water out the other end, into the big hollow space in the middle. Pyrosomes look terrifying, but like many giants of the sea, they’re actually filter feeders.

A small pyrosome colony. Each basket-like structure is the gut of an individual member. Photo by Stefan Siebert, used with permission.
A small pyrosome colony. Each basket-like structure is the gut of an individual member. Photo by Stefan Siebert, used with permission.


And it’s this filter feeding that gives pyrosomes their rocket power. Well, almost. My friend, aerospace engineer turned biologist, Henry Astley, put it like this: “jets have to do four things: Suck, squeeze, bang and blow.”  Suck in air, compress it, explode some fuel, and blow the resulting force in the direction opposite where you want to go.  The squeeze and bang part need compressible gas and fuel. Two things pyrosomes don’t have. But the other two, suck and blow, are expert territory for these guys.

A closeup shot of individual members of the pyrosome colony. With the basket-like gut visible. Photo by Stefan Siebert, used with permission.
A closeup shot of individual members of the pyrosome colony. With the basket-like gut visible. Photo by Stefan Siebert, used with permission.

Many animals use sucking and blowing movement to get around. Squid and octopuses use it, as well as certain types of jellyfish, which move like squid by sucking water under their bell and then shooting it out. This is a pulsing jet-like movement. Only one opening doing both the sucking and the blowing, and therefore the animal moves in fits and starts. Not at all like the smooth, constant stream of a true jets engine. The only animal to move with such fluid jet-like propulsion is the pyrosome. Because each member noshes on tiny plankton, they must constantly suck water in and over their baskets, and constantly blow waste out the hollow center. Thus they are moving at a steady, albeit painfully slow, speed.

So they’re giant, terrifying looking, and trolling through the depths of the ocean, waiting for you to swim in one end and get stuck.  Maybe. But fortunately, in addition to being slow moving filter feeders, they’re also delicate and fluffy. One diver described a pyrosome saying “it felt like an exquisitely soft feather boa” [2]. And this is why I almost cried when I saw my first wee pyrosome.  Despite their improbable nature, these horrifying giants, the spawn of the worst movie villains, are actually delicate and fragile. The bizarre unicorns of the sea.

Update (03August 2013): Do not swim inside a pyrosome. While they are said to be quite soft, K Gowlett-Holmes reports finding a 2 meter (~ 6.5 ft long) pyrosome with a dead penguin trapped inside. K Gowlett-Holmes writes in a comment below: “The penguin had obviously swum in the open end of the tube then couldn’t turn – it was jammed in the apex of the pyrosome and its beak was just poking through the colony matrix. Even fairy penguins are quite strong – the fact it could not break free shows just how tough some pyrosomes are”.  O_O

Work Cited

[1] Edward E. Ruppert, Richard S. Fox, Robert D. Barnes (2003). Invertebrate Zoology: A Functional Evolutionary Approach Seventh Edition. Brooks/Cole Thompson Learning, Belmont, California.


65 Replies to “The 60 foot long jet powered animal you’ve probably never heard of”

  1. Great article! What is the benefit of being so big? Does it mean the animal(s) can move faster and therefore suck in more water (and nosh more)? It seems like bigger might also equal more fragile in this case.

  2. Good question! I don’t have a concrete answer, but maybe it has to do with safety (?). Once they reach a certain size it may be harder to eat them. For example, many medusa jellies eat other gelatinous animals, but I don’t know of any jelly that could consume something this big. I’m just guessing though, it’s a good question.

  3. Very interesting. I didn’t realize they got so large. Now I have another modern example of a large colonial planktonic organism (besides the Portuguese man o’ war) that I can cite when I talk about graptolites in my Historical Geology class.

  4. How is it these things aren’t eaten by predatory fish? Do they have nematocysts or something similar?

  5. They are intensely, *intensely*, bioluminescent. Wiki quotes T.H. Huxley saying: “I have just watched the moon set in all her glory, and looked at those lesser moons, the beautiful Pyrosoma, shining like white-hot cylinders in the water” (T.H. Huxley, 1849). I can’t even imagine what one of these 60 foot long animals would look like at night. But I bet such a display would make a predator think twice. I’d love to see one lighting up, but couldn’t find any video or images to show.

  6. It is very easy to see why the early biological oceanographers had no idea about the true nature of Pyrosoma. All they were able to bring up in their nets were bits and pieces of the whole colony; extremely likely even today.

  7. How astonishing and beautiful! I was completely unaware of these life forms. Thank you so much for posting this!

  8. Hi, I’m researching these right now for my masters thesis, just thought I’d say its great to see someone else writing about them. Nice to see them from another person’s perspective for a change! If you’re interested at all I wrote a blog at the beginning of my research here and breaking the dry spell of papers on them, I should be submitting a few by the end of the year (sadly I have no video of them alive though, mine were all delivered in alcohol). Nice piece!

  9. WOW! I’m so glad someone is working on these guys! I hope you don’t mind, I reblogged your post on Great article, thank you so much for bringing it to my attention!

  10. No thats brilliant thanks, always nice to have a piece I’ve written actually getting read! Yeah there’s barely any research thats been done on these animals for decades, I’m aiming to be publishing a quartet of papers and hoping that sparks a bit more interest in them as a result, they’re so unusual but so poorly known. A biochemist should do a PhD on them imo. If you’re interested in anything I’m looking at I’d be glad to answer it. And glad to see someone else in the world is writing about them!

  11. The big long thing in the picture is a salp, not a pyrosome. They are not mobile creatures, and are mostly at the mercy of the currents (which they are very good at exploiting). The individuals join together to maximize feeding.

  12. I don’t think it is a benefit issue. These aren’t singly organisms that need to justify their size as an adaptation. (benefit toward reproduction). They are millions of little organisms. As long as they have food, they are going to reproduce. If they have enough food to support a giant colony, their going to create a giant colony.

  13. It is a pyrosome, probably Pyrosoma spinosum, and while they are at the mercy of the current to some degree, they are self propelling. I’d recommend googling it for additional information (some of the pictures online are awesome. This one in particular is fantastic). Pyrosomes are related to salps, they are in the same group (Thaliacea), but they are not salps.

  14. Good point Ben. Just because a feature exists, doesn’t mean it’s adaptive :)

  15. The long one at the start of the video is Pyrosoma (or Pyrostremma) spinosum – this colony is about 15m long. While they do drift with the main water body, they are fully capable of propelling themselves slowly along, and will actively try to avoid large objects in the water. Smaller species, eg Pyrosoma atlanticum, can move faster and can be actively seen moving. There are also several species of salps in the video – while they are more obviously pumping water, they actually appear to be more at the mercy of the water currents – salp colonies do not seem to move in a co-ordinated way like pyrosomes. These are in situ observations. This is a superb area for in situ observations of oceanic gelatinous plankton – we see giant pyrosomes every few years, but we see salps, ctenophores, siphonophores and other gelatinous plankton regularly, sometimes in incredible numbers. Have a look at the other videos on our channel.

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  17. Do these break apart if touched, and how sturdy ARE they to currents or punctures or fish swimming through (or prodding hands??)

  18. The little one I found was firm, but it’d also been fixed in chemicals. However, I suspect they’re pretty tough, check out this article showing one that accidentally wrapped around an instrument and was brought aboard a ship.

  19. Great video. I love the music. Can anyone tell me what it is or point me towards it, please?

  20. The texture of the colony varies with the species, but they are all fairly firm but flexible – they are not like ctenophores, many of which disintergrate if touched. You can handle pyrosomes, and it takes some effort or a sharp edge to damage them. The smaller P. atlanticum is particularly tough – they regularly come up intact in commercial fish trawls, and are tough enough that a fairy penguin that swam up inside a large one was trapped and actually drowned (we found the pyrosome with the body still inside it, jammed right in the apex with the beak almost through it).
    The music on the video is an untitled royalty free track we have had for many years.

  21. WHAT?! A penguin got stuck in one and died?!?! Oh please, PLEASE tell me there is a picture/video of this.

  22. Unfortunately, we have no pictures or video. This was over 15 years ago, prior to us always having a digital camera on the boat. The pyrosome was spotted floating on the surface and when we picked it up we realised that there was a dead penguin inside it. It was a very large Pyrosoma atlanticum, about 60cm long, and at that size they are quite tough. The penguin had obviously swum in the open end of the tube then couldn’t turn – it was jammed in the apex of the pyrosome and its beak was just poking through the colony matrix. Trapped in there, it drowned. Even fairy penguins are quite strong – the fact it could not break free shows just how tough some pyrosomes are.

  23. Phylogenetically, where do they stand? And how are they biologically classified?

  24. well that is a little unnerving O_O Death-by-pyrosome. Poor penguin. The moral of this story? Do not swim inside a pyrosome. Eep.

  25. They are thaliaceans– in the same group as salps and doliolids. Thaliaceans are in turn tunicates– a group that includes sea squirts. Zoom out a bit more, and we’re now at the Chordata, a group that includes humans. So we’re rather closely related, relatively speaking :)

  26. I combined these with giant siphonophores, in my undersea D&D game last year, to make a fearsome and memorable beastie.

    The fact that they are bioluminescent makes me want to see one at night, now.

  27. The unique thing about their bioluminescence is that, in addition to being triggered by touch, it is light activated, so you can make them glow with a flashlight, It will also propagate slowly from one end if the colony to the other. On big ones, people have reported writing their name on the side in luminescence. It is not even known for sure if the light is from bacteria or intrinsic (maybe Dave Bennett [above] will sort this out!). (Dave, we could send you live or flash frozen samples in occasion.) Lots of mysteries left for an animal that has been known for so long… Tease: I have some cool pix of their glow, but can’t share them yet….

  28. I may indeed have sorted the bioluminescence mystery out! Though with the inevitable caveat of ‘further research needed’ of course… I’ll have to be quiet until the end of the year when my manuscripts are submitted though sadly. Never heard the reports of people writing their names on the side of big ones before, thats pretty cool. I’d have thought the luminescence would spread out through the colony too quickly for that to work though?
    Thanks very much for the offer Steve! Out of interest how would you propose sending live samples? Sadly my masters finishes at the end of September though, so soon I’ll be scientifically homeless. Depending on what happens at the end of the year I may have to take you up on that though…

  29. You need to *tell* people to refrain from swimming inside a huge sea creature?!! Seriously?

  30. Hi, I was wondering if it may actually be possible to take you up on the offer? Obviously my university could cover all postage costs etc. If you’d like it for discussion out of a comment section my email address is davidrbennett88[at]gmail[dot]com. Cheers!

  31. It’s not really jet propulsion but suction propulsion through the zooids at the nose. If it were really jet propulsion then it would be unstable and you’d need some clever method of keeping nose aligned with tail – such things are probably beyond pyrosomes. With suction propulsion the nose pulls and everything else just follows along.

    I’m amazed the big ones don’t get chewed up by e.g. fish. They can’t all be fooled by bioluminescence.

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