With a comically tiny mouth and a blunt cauliflower tail, the ocean sunfish is little more than a swimming head. Which is, in fact, its name in German. Grotesquely oversized, these monsters appear to loll helplessly on the ocean surface, sunbathing like blobby grey rafts. They support their great bulk on a meager diet of jellyfish, which means they have to eat a lot of them. Unfortunately, their snack of choice drifts along as far as 2000 chilly feet below the surface, and these tropical loungers don’t care for cold. In response, the Mola mola has evolved a suite of highly unusual adaptations. Can humans find inspiration in this strange diving expert? Find out in !
Image by blueSkySunHigh
An adult sunfish may be 10 ft long and 14 ft across, and weigh in at up to 5000 lbs. The world’s heaviest bony fish also has the shortest spinal column and the fewest vertebrae, losing his tail and many of his bones to the ravages of evolutionary time. Nowadays, the mola’s skeleton is mostly lighter cartilage, allowing him to grow very big.
With this huge frame and no forward thrusting tail, the sunfish has to get around with a pair of tiny pectoral fins. Looking at this guy, you can’t help but find yourself thinking “Go home, Evolution, you’re drunk.” He usually swims slowly and carefully. But this monster is no drifter. Molas in Southern California have been tracked swimming close to the speed of cruising yellowfin tuna. He can move when he wants to. And not just forward, but up and down.
Although we usually see the sunfish basking passively at the surface, he actually migrates vertically during the day, dining on jellyfish living below the warm surface water. Because he perishes quickly in cold water, researchers think his habit of sunbathing on his side may help him “thermally recharge” after deep dives.
A sunfish caught in 1910, with an estimated weight of 3500 lbs. Image via Wiki Commons.
The mola has another trick for jellyfish-diving. Unlike most bony fish, he has no gas-filled swim bladder, and therefore doesn’t need to worry about volume changes from pressure in deep water. In fact, this fish has almost the exact same body density as seawater. He has neutral buoyancy at any depth, thanks to a thick layer of water-rich, incompressible, gelatinous tissue just below his skin. As a result, as he moves forward, the ocean sunfish can also move vertically, using minimal energy.
Could we borrow some of these ideas for ocean-based industries? How about wetsuits with constant buoyancy and thermal insulation, at any depth or pressure? Or for submarine robotics, used in underwater construction or dives?
And here’s another neat idea: Mola’s don’t chew their jellies. Instead, they suck them in and out of their tiny, beak-like mouths until they’re reduced to Jell-o. Then, they slurp them down into their bellies, where a lining of mucus keeps them from getting stung. I’m sure it’s like really exceptional hospital food, only better.
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An evolutionary biologist, writer, sustainability expert, and passionate biomimicry professional in the Biomimicry 3.8 BPro certification program, Dr. Tamsin Woolley-Barker blogs at BioInspired Ink and serves as Content Developer for the California Association of Museums‘ Green Museums Initiative. She is working on a book about organizational transformation inspired by nature.