This Fish Can Support 300 Times Its Weight With a Super Suction Cup

I was going to wait until the end of this caption to mention that this fish is in fact dead, but PETA doesn’t wait to get to the end of captions before sending angry emails. Anyway, this is the world’s most disturbing ventriloquist dummy, the clingfish, which had no idea what it was getting into when it checked the “donor” box at the DMV.

Dan Goodman, who refers to himself as SpiderDan so as to not waste all that time on hyphens like Spider-Man, set out more than 30 years ago to build a suction cup he could use to ascend the 110-story Sears Tower. Totally retooling the suckers that window glaziers use to transport glass, he donned a Spider-Man suit on May 25, 1981, and climbed the thing in seven and a half hours. He was of course arrested at the top, but after Sears came to his defense, he got a $35 fine and was released.

Impressive, SpiderDan, very impressive—for a man with a fear of hyphens. But stuck fast to reefs and sea cliffs the world over is a critter with a suction cup far more impressive than yours. This is the clingfish, which sports a belly sucker that can support a staggering 300 times the fish’s weight.

The 161 known species of clingfish vary greatly, from a tiny one that sticks itself to the individual spines of sea urchins, to a deep-sea type with hardly any sucker at all, to a relatively giant species the size of your forearm (no, not yours, Shaq—this doesn’t apply to you). Perhaps one of the best-studied species, thanks in part to fish biologist Adam Summers of the University of Washington, is the northern clingfish, which calls the Pacific coasts of Mexico, Canada, and the U.S. its home.

While SpiderDan had the benefit of human ingenuity, the clingfish has the benefit of evolutionary time. Its sucker, according to Summers, is in fact made of its pelvic and pectoral fins, which have converged to form a disk. All around the edge of this disk are tiny hexagons that to the naked eye look totally flat.

“But when you look at them under a scanning electron microscope,” said Summers, “you see the top of each of those hexagons is a field of spaghetti, of long, thin hairs that are the same aspect ratio and length as the hairs on geckos’ feet or spiders’ toes or beetles’ feet.”

The clingfish’s sucker is made up of highly modified pectoral and pelvic fins. The pectorals are normally on the sides of fish, somewhat analogous to our arms, so the clingfish therefore is not able to high-five other fish without awkwardly sticking to them. Because of this, it suffers from social anxiety. You and me both, clingfish. You and me both.

This is pivotal in keeping a strong hold. Not only does the clingfish’s highly compliant sucker conform to bumps on rocks to get a good seal, all of those hairs cause a lot of friction. “They keep the edges of the disk from sliding,” said Summers, “so on a rough surface the hairs interlock with the surface, and by interlocking with the surface they’re able to keep the cup from moving.” Movement, you see, is a suction cup’s worst enemy.

More on that in a second, but first, some suction basics. When you press a suction cup against a surface, you force much of the air out of the cavity, creating a partial vacuum. The sucker holds its place because the surrounding air pressure is so much greater than the air pressure in the suction cup. It’s actually atmospheric pressure that keeps it it stuck.

A scanning electron microscope image of the clingfish’s hexagonal pads and another zoomed into its many clingy hairs. Why yes, the clingfish does in fact condition. Thanks for noticing.

Now, think about the last suction cup to fail on you, like those on your shower caddy, perhaps. That’s a weird request, and for that I apologize. But stick with me. It probably started sliding down under the heavy burden of shampoo, and when it did, the amount of air leaking into those suction cups accelerated. The air pressure inside got closer and closer to the surrounding pressure, especially if the sucker began moving over grout, until the suction cup catastrophically failed.

Let some clingfish loose in your shower, though, and they wouldn’t have the slightest difficulty holding on indefinitely. (Well, for a while at least. Like many fish in the intertidal zone, which is submerged at high tide and dry at low, clingfish can spend considerable time out of water, breathing with their gills and even absorbing oxygen through their skin.) The clingfish’s sucker, far more pliable than plastic suction cups, could fill in the grout gaps, and those innumerable microscopic hairs would provide plenty of friction to keep the fish from sliding around. The same principles go for it suctioning in the ocean: as long as the clingfish can keep the pressure in its sucker low enough, it maintains its hold.

And now we come to the why. Why on Earth would such a structure evolve if the clingfish has never been asked to support shower caddies?

“There’s several purposes for it,” said Summers. “One is they are able to stick to rocks when they’re in the intertidal, when they’re being battered by waves. So it keeps them still in high-energy environments.”

“Please don’t notice me, please don’t notice me,” whispers the limpet. “I finally paid off the mortgage on this rock last week.”

The second purpose is rather more clever. The northern clingfish hunts limpets, round little mollusks that themselves cling tightly to rocks. “And when they see one,” said Summers, “they get really close without touching it and then they suck down to give themselves a nice solid launch point. And then they open their mouth and thrust forward while remaining sucked down and jam their lower jaw teeth under the limpet and suck it off the rock.”

Elsewhere in the clingfish family, species too tiny to assault limpets are giving up their own secrets. Just last month, researchers observing Caribbean clingfish that has been closely studied for 260 years discovered something entirely new: the bones that support their gill covers have evolved into venomous barbs. Indeed, according to Summers, who was not involved in the study, these are the world’s smallest known venomous vertebrates.

Read more at Wired Science