Seeing the Unseen: Spineless Version

Jellyfish are fascinating. I hadn’t realized as much until my eyes were opened reading Spineless by Juli Berwald.  Part-memoir, yet chockfull of scientific facts, Berwald takes you around the world in her quest to consume all things jellyfish. Yes, she even decides she has to try cooking and eating some! The subtitle of the book is The Science of Jellyfish and the Art of Growing a Backbone. I found it even harder to put down then the excellent I Contain Multitudes by Ed Yong, and read multiple chapters in a single sitting. I will just highlight one of them.

Chapter 7 is titled Seeing What’s Not There. Having pondered Invisibility Rings and Making Visible the Invisible in chemistry, this chapter was particularly fascinating. Yes, it’s about jellyfish transparency – but there are many other equally fascinating denizens of the deep highlighted by Berwald. The tale of transparency begins with her interviewing the jellyfish scientist, Richard Harbison, asking him why so many jellyfish are transparent. His response: “The question is, why isn’t everything transparent?”

Berwald ponders this question and writes: “In the ocean, with nothing to hide behind and nothing to blend into, being opaque puts you at risk of being seen. Being seen means being eaten. Invisibility is also an advantage if you are a predator. Prey are more likely to steer clear if they can see you. Prey might just stumble into your grasp if they can’t. Transparency is an underwater invisibility cloak; the ultimate disguise.”

Posing Harbison’s question to another scientist, Sonke Johnson, comes the reply: “because it’s hard.” A surface-dwelling creature only needs to blend into its surroundings; a “surface paint job” might suffice. But for an ocean roamer, one needs to do much better. Berwald writes: “Some animals do this by being extraordinarily thin. Light passes through such animals so easily that it encounters almost nothing to scatter it. One supermodel of transparency is a comb jelly called the Venus girdle, which is less than an inch thick, but can stretch a yard and a half in length. The animal’s svelteness decreases scattering so much that in photographs it looks like just a few white lines dashed off by a sketch artist.”

Berwald anticipates the reader’s next question. “But many jellyfish aren’t flat; they are bulbous round things.” Having previously discussed jellyfish locomotion and buoyancy powered by its amazing mesoglea, it turns out that “watery mesoglea is a brilliant solution to being transparent… [because] light passes through the mesoglea nearly the same way it passes through the ocean.” Berwald just has a way with words. “Jellyfish are physically fat and optically skinny.” But there’s more. “And being physically rotund matters a lot more in the open ocean, where there’s nowhere to hide, because even the best invisibility cloak isn’t perfect… [If] spotted by a predator, it’s always better to have heft on its side. No one wants to tangle with a big dude. The mesoglea allows a thin jellyfish to masquerade as a jumbo version of itself, and it does so on the cheap… jellyfish get a lot of heft, not for free but at a significant metabolic discount.”

I’m essentially quoting Berwald to give you a flavor of her engaging prose, and also because I would do a lot worse trying to capture what she writes in my own clumsy narrative. You’ll have to read the book (and it is a delight!) if you want to know why the blood belly comb jelly has a currant-colored stomach. I also learned that in Spanish, jellyfish is medusa. And yes, Berwald appropriately weaves in the Greek mythology in her book. Jellyfish might hold a clue to immortality. And their famed barbs are more sophisticated than I could have ever imagined. (Below is the Australian Box Jellyfish, picture taken from World Atlas.)

As for humans living on a terrestrial surface terraformed into urban sprawls, a camouflage cloak would have to be extremely sophisticated to mask the presence of its wearer. A true cloak of invisibility, like the one handed down to Harry Potter from his ancestors, would be a marvel indeed. The best we can do with our modern optics and sensors is probably an invisibility shield. Several variations have shown up in movies featuring hi-tech gadgets. But in the realm of the merpeople, a hi-tech invisibility wetsuit would be within reach. Then again, it depends on who’s looking and how they are looking. Not every creature exploits the visual, especially if there’s little light in the depths.

In any case, I am looking forward to my next visit to an aquarium. Having read Berwald’s fantastic book, I will never look at jellyfish the same way again. I’ll be spending time looking a lot closer and harder, to see what I had not seen before!