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Doug Muir on one of Nature’s more striking creations…

There’s been a a certain amount of negativity floating around lately. So, let’s talk about a toxic, venomous freak of nature and the parasite that afflicts it.

Biology warning, this gets slightly squicky.

Let’s start with the toxic, venomous freak of nature:  the Portuguese man-o’-war…

… So it’s a jellyfish.  Except it isn’t really: it’s several jellyfish, smooshed together.  And here’s where the “freak of nature” part kicks in.

I mean, yeah, strictly speaking nature has no freaks; every species that exists, belongs; everything is a product of evolution and Life’s Rich Pageant, yadda yadda.  But the Portuguese man-o’-war  — Physalia physalis, for you biologists — is honestly kinda freaky.  Because Physalia is a colonial organism.

What this means: a single Portuguese man-o’-war is composed of four or five separate animals.  (We’re not actually sure how many.)  One animal is the balloon-sail-thingy on top; another is the stinging tentacles; another is the digestive system; another is the gonads.  And they’re completely distinct organisms.

How this happens: when a Physalia egg is fertilized, it starts dividing, like every other fertilized egg.  But pretty quickly it breaks apart into two and then more distinct embryos — genetically identical, but physically separate.  And those embryos develop into completely different creatures.  Then, later in development, those creatures re-attach to form a single Frankenstein organism.  The various parts have their own nervous systems, which don’t seem to connect.

Here’s an analogy: imagine that before birth, you are identical twins.  But instead of growing into two babies, one twin grows into a bodiless head, the other into a headless body.  Then just before birth they stick together, but they don’t actually merge back into one.  No, going forward you are a bodiless head glued on top of a headless body, ever after.  It’s kind of like that.

Now, colonial animals aren’t unknown in nature. But most of them are either dinky (Volvox, don’t ask) or they’re big, but it’s basically cut-and-pasting the same creatures over and over. So, some corals are colonial, but all this means is that the individual polyps have grown into each other to produce a sort of living carpet interlaced through their stony skeleton. But the man-o’-war is a respectably large animal — they can grow as big as a large house cat — and so are its colonial components. And the components are extremely specialized: the float-animal part of it looks and acts nothing like the tentacle-animal part.

Physalia is by far the largest complex colonial animal.  And — this bit is odd — it doesn’t have any relatives.  It’s the only genus in its family.  Put another way, within the jellyfish it has no siblings and only a few very distant cousins.  (One of which is the ridiculous creature known as the Flying Spaghetti Monster Jellyfish, but never mind that now.)  It’s a very successful organism!  There are millions and millions of them, found all over the world in tropical and subtropical oceans.  So you would expect to see speciation, different relatives — big ones, little ones, a bunch of variations on a theme.  More on this shortly.

But meanwhile, the whole “colonial animal” thing looks like evolution’s first attempt to figure out, you know, organs.  I mean, the first multicellular animals were probably sponges, and sponges don’t actually have organs. But more complex animals have distinct and differentiated organs, modules of specialized tissue performing particular functions, because those turn out to be super useful.  Physalia and other colonial animals look like a beta-test platform for this new “organ” technology.  Most of the animal kingdom moved on to “oh wait, why don’t we just have one single creature that grows the different modules inside it”, but a few colonial animals stuck with Plan A and made it work.

Okay, so that’s the “freak of nature” part. What about the “toxic and venomous”?…

Read on to be astounded: “Occasional Paper: Four Hidden Species of Portuguese man-o’-war,” from the always-illuminating @crookedtimber, via Ingrid Burrington‘s exquisite newsletter, Perfect Sentences.

* “The purple, formalized, iridescent, gelatinous bladder of a Portuguese man-of-war was floating close beside the boat. It turned on its side and then righted itself. It floated cheerfully as a bubble with its long deadly purple filaments trailing a yard behind in the water.” – Ernest Hemingway, The Old Man and the Sea

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As we tangle with tentacles, we might spare a thought for Columbus Iselin; he died on this date in 1971. An oceanographer, he taught at both Harvard and MIT, and was a long-time Director of the Woods Hole Oceanographic Institution, which grew materially in both scope and impact under his leadership.

His own work included both the invention of the bathythermograph and other deep-sea instruments responsible for saving ships during World War II and foundational scholarship on the oceanography of the Gulf Stream… where, of course, one can find the Portuguese man-of-war.

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