Lessons from the Sea Squirt

The sea squirt is a squishy-looking, unprepossessing marine animal that somewhat resembles a hot water bottle with two nozzles. Cilia (hair-like structures) at the opening of one nozzle sweep salty water into the creature’s body. Inside, the water is mined for oxygen and nutrients before being vigorously ejected through the other opening. Such minor explosions of waste matter give the sea squirt its picayune name. Occasionally, a sea squirt releases eggs and sperm—its ability to produce both male and female gametes being the singular happiness of the hermaphrodite. These free-floating future-capsules wander about until they find the sperm or eggs of other sea squirts, enabling them to fertilize themselves into tadpole-like sea squirt spawn that will grow up to be shaped like hot water bottles.

It all seems, on the whole, a simple existence. But wisdom emerges from the strangest of places. Could the sea squirt be your new guru?

Us and Them

Although they certainly don’t look anything like us, sea squirts actually have quite a bit more in common with human beings than they do with, say, corals. They belong to the same phylum as Homo sapiens: Chordata. And they fit there because, although they don’t have a backbone (most other chordates are vertebrates, like us), their larval babies do have a notochord. A notochord is a sort of flexible rod made of cartilage that runs down the back and serves as a sheath for a small number of nerve fibers—it’s worth noting that as embryos, humans, too, go through a stage where a notochord is the only spinal cord we have. The sea squirt’s notochord is part of a primitive nervous system that allows it, in its larval stage, to respond to the presence of light and navigate using that information.

Effective navigating is important partly because the larval sea squirts have to nose around in the water for nutrients as they grow, but also because they are looking for something else: a permanent home. In their adult form, sea squirts are sessile organisms. The term comes from the Latin for “seated,” and refers to the fact that once they’ve found what looks like a good place to be, sessile organisms figure they’re done with moving, thank you very much, and sit there until they expire. In the case of sea squirts, good places to be are usually rocks, cement breakwaters, the hulls of ships, or sea shells or crabs that are large enough to accommodate their bodies.

If You Don’t Need it, Lose It

Having located its sweet spot, the larval sea squirt attaches itself to the chosen surface with a sucker and begins to metamorphose. Where it once had gills, it develops the entry and exit nozzles that help it to eat. Its twitching tail disappears. And—since it no longer needs to move or find food, which will forevermore be brought to it on the currents of the sea—part of the sea squirt’s metamorphosis involves merrily absorbing its tail and notochord, including those primitive nerve fibers. As it does so, it achieves its final form and receives an additional burst of energy into the bargain.

Researchers and journalists alike are fond of using the sea squirt as a metaphor for intellectual laziness in humans. “When it no longer needs to think,” they chuckle, “it eats its own brain!” “Use it or lose it!” they caution happily. There’s certainly something to be learned from the sea squirt’s unusual life cycle, but let’s be fair: 1) a notochord is hardly a brain, and 2) what the sea squirt is doing isn’t really self-cannibalism. We wouldn’t, after all, think to describe a frog as having eaten its earlier incarnation, the tadpole. If you ask me, what’s really interesting about these odd little creatures is not how lazy they are, but—like so many species in nature—how wonderfully pragmatic. How many of us have held on to a faded idea of who we really are, long past the point at which we ceased to be that person in reality? Who among us hasn’t tried without really thinking to force ourselves into a shape, or a personality, or a career, that just no longer fits? No more! Think of the sea squirt.

Don’t Put All Your Eggs in One Basket Bud

The fact that sea squirts absorb their notochords once they become defunct is just one example of their no-nonsense nature. Just as fascinating is the way they reproduce asexually. For many species of sea squirt, tossing out eggs and sperm into the water isn’t an efficient enough means of multiplying. Their repertoire includes a process called budding, which enables them to rapidly form colonies of sea squirts. In order to bud, a mature sea squirt forms dozens of tiny outgrowths on its own body that each contain a self-sufficient collection of stem cells. These multiply through mitosis. Eventually, the cells inside a bud organize themselves into a hollow sphere, create a thicker layer of cells on the outside of that sphere, and form chambers and organs within it: a process that takes about two weeks. At the end, voila! A new sea squirt emerges called a “zooid,” genetically identical to the first.

But not every bud makes the cut. According to a recent study of the sea squirt species Botrylloides leachi published by Israeli researcher Yuval Rinkevich, “only the fastest developing bud in a fragment reached the final zooid stage; the others were absorbed into the colony.” Rinkevich calls this a “race for predominance;” I call it an analogy for the kind of growth lots of us go through as we search for the perfect incarnation of ourselves. Why not try a dozen different versions of yourself before keeping the one that seems the strongest, the wisest, the most suited to where you are in your life right then?

If there’s something to be learned from the sea squirt, maybe it’s the call to take stock of where you are, what you want, and what you need to get it now. And then, if there happens to be a tail or a cartigilanous skeletal rod or an underdeveloped bud lying around that you don’t need, why, sea squirt-like, simply stop devoting any more of yourself. Let it melt away. Regain some energy—and use it to grow new, more relevant, and stronger parts. If not all of them survive, that’s okay. The ones that matter will.

At any rate (most likely) you won’t end up looking like a hot water bottle.