dance of the sea cucumber

In this post, I want to explain why something is funny.

The Sea Cucumber is an inspirational beast. It is an ancient sea-dwelling tube-shaped invertebrate, both boneless and brainless. Some kinds are only as big as your thumb. Some of the biggest ones are about as long as an adult human is tall. Long ago, denizens of the ancient warm oceans discovered the advantage of linear body shape. To be able to go forwards, towards good things (like food, shelter, and mates) and away from bad things (predators, the cold, one’s own feces) was proving an extremely worthwhile behavioural suite. Sea cucumbers appeared when radial pentamerists were discovering the wonders of linearity and bilateralism. The sea cucumber’s ancestors were armored echinoderms, ‘hedgehog-skinned’ animals like starfish and sea urchins. They stretched out, and the exoskelatal plates, that had shielded their forebears, separated and shrank to become tiny disparate (quite beautiful) little ossicles sprinkled sparingly throughout their now flexible hides. Embracing linearity, they shed their rigidity and attained the gift of speed.

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Sea cucumber ossicles

Cucumbers retained a rough five-sided symmetry about the axis of their length, but on three of their corners grow a host of little blobby legs to crawl around on the ocean floor. On their two upper corners they grow fewer and more vestigial blob legs. By undulating their bodies and waving their blobby legs they can swim as well as crawl.

At a cucumber’s front end, its mouth end, these blobby legs are specialized into a ring of food gathering scooper arms, with an accompanying ring of nerve tissues that coordinate the efforts of these little scoopers, and trails of nerves along the length of a cucumber’s tube-shaped body to direct its legs. Earlier on, I called sea cucumbers ‘brainless’. I was not trying to be mean. Their nerve system is quite effective; it just does not seem to have a central processing location. If, through some misfortune, a sea cumber looses its head end, then the legs will still walk the animal around and the front end, less efficiently, still collects food. The sea cucumber’s food is tiny ocean plants and animals that can be digested without chewing.

Sea Cucumber
the formidable sea cucumber

In the ancient ocean, the sea cucumbers were formidable beasts. Masters of their world, they could go anywhere, purposeful, fast, and effective. But, alas, they evolved in a soup of even more fearsome beings. Other creatures were taking bilateralism and linearity to crazy extremes, animals with real site-specific brains, streamlined animals with fins, plated animals with articulated legs, monsters that could focus on tasks in ways the sea cumber could not even imagine, could scramble across the ocean floor or swim through the water at speeds that the sea cucumber could not dream of achieving. Many of these rivals could see (and, belatedly, some species of sea cucumber evolved rudimentary light sensitivity). But the most terrible beasts of all had claws, had jaws with teeth, innovations that sea cucumbers could only have viewed (in their sightless, brainless minds) with utter dismay.

Out foxed, out maneuvered, their armor long abandoned, you would think sea cucumbers were doomed. But these apparently helpless tubes of slow, stupid, tasty muscle, they came up with a trick. When they got bitten or jabbed, when they felt threatened, they turned inside out! (The formal term is ‘evisceration’.) They pulled out their entrails and floated in a cloud of their own offal. The attacker, expecting a nice snack, got a surprising and unpleasant snoot full of upchuck, guts and feces. Many an otherwise enthusiastic predator found its appetite suddenly dampened. (Some sea cucumbers refined the technique, actually making their guts poisonous or gluey, so that potential predators, who did not retreat quickly, could be seriously hurt by the gross cloud.) It takes days for the cucumber to twist right-side-in again and grow new viscera, but despite the cost, enough sea cucumbers survive enough encounters with superior adversaries that, eons later, sea cucumbers are still with us in abundance.

I first learned about the sea cucumbers and their intriguing defense behaviour when I was an adolescent, and, as any half-grown primate would, I hooted with laughter. I have enjoyed the story ever since. But, an illustrative question for this post is: who am I to laugh at the sea cucumber? Or, maybe a better way to put it is: what is so funny about the sea cucumber’s defense?

The answer is that the sea cucumber’s behaviour is totally absurd from the perspective of a highly-evolved primate. You and I, my good reader, if in serious danger, would run (because we are fast and tricky), or turn and fight (because we have fists to punch with, feet to kick with, and we might have a weapon: a stick or knife or gun) or we might call 911 (because we have cell phones and a complex culture). We would not consider, however briefly, turning ourselves inside out as a practical way to defend ourselves. Judged in human terms, the sea cucumber’s response to danger is so profoundly impractical as to be comical.

But the flip side is that the sea cucumbers have been turning themselves inside-out for a long long time, contorting before their adversaries, vomiting and defecating their way to safety for four hundred million years. Highly-evolved primates have only been doing sensible highly-evolved primate things to get away from danger for a few hundred thousand years. So sea cucumbers have been doing their routines for roughly one thousand times as long as we have been doing our routines. And we have done industrialization for only about one half of one-thousandth of our time here, less than one millionth of the time cucumbers have been dancing in the sea.

So, objectively, the sea cucumber’s behaviour is very effective. And it looks funny only when seen through the temporally distorted lens of human experience. Of course, being human, as I am, the distorted view is my default perspective. (Probably yours too, good reader.)

We are highly-evolved primates. We have evolved these amazing metaphorical teeth and claws, more terrible than any other on our world. We have nuclear missiles enough to cook our biosphere, to plunge it and ourselves into extinction before noon any day of the week. We could hold back a bit, and just initiate a nuclear winter. Or we could keep those missiles on-hand, unused but available, maintained by our great industrial civilization. Then it becomes a race to pollute our biosphere to collapse, or initiate a global warming catastrophe. By any objective assessment, we, the highly-evolved primates, are the ones headed for extinction.

And who will be laughing then, eh?



  1. As a fan of the sea cucumber, I love this little meditation on their soft power. I wonder, do you suppose there is any sense in which the explosion of social media, where people willingly spill their guts all over a public sphere, could be seen as a sea cucumber tactic? Our privacy cannot be threatened, if we put it all on view, and maybe our pettiness, obsession with sex, appearance, social status etc, is yucky enough to keep us safe? Mind you, if that’s the case, I wonder what our predator is?

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