Glow-in-the-Dark Shark Makes Cookies Out of Flesh

Marathon swimmer Mike Spalding was 10 hours into an epic 33-mile voyage between Maui and the Big Island when his escort boat lost sight of him. Being the middle of the night and all, the captain was forced to fire up his lights to reestablish contact with the kayaker at Spalding’s side.

This, ironically enough, is the absolute last resort when you get lost swimming in the darkness. With the kayak’s light now blazing as well, the creatures of the nighttime sea began to take notice. Squid amassed around Spalding as he slogged on, forming a slowly moving bait ball. He took a hit from one, and then another and another. After the fourth bump, Spalding felt a sharp pain in his chest.

It was the first bite, albeit just a nibble. The 62-year-old (that’s not a typo) Spalding broke for the kayak.

“As I was eggbeatering to get into the kayak with my legs perpendicular to the surface of the water, I felt this sharp hit on my leg,” he told WIRED. “It wasn’t painful, but it was like you got punched or something. And so I ran my fingers down my calf and I felt this hole.

“It’s a bigass hole.”

Spalding had earned the dubious title of first living human confirmed to have been attacked by a cookiecutter shark, which gored a 3-inch-wide crater in his leg. At no more than two feet long, this diminutive terror nevertheless packs a set of teeth that are bigger than any other shark relative to body size, according to George Burgess, an ichthyologist and director of the Florida Program for Shark Research at the Florida Museum of Natural History. It’s a glow-in-the-dark evolutionary marvel of the open ocean that takes on beasts hundreds of times its size, including submarines. And it almost always wins.

The cookiecutter shark doesn’t set out to kill its prey. Instead, it makes sneak attacks, using its fleshy lips to suction like a Nerf dart onto a whale or tuna or pretty much any other large critter. Its saw-like teeth easily tear through flesh as it “rotates its body in a 360-degree fashion around and around and around like a drill,” said Burgess. “And as it’s digging in, it gradually closes its jaw little by little, thereby making the crater wound as opposed to just a cylinder.”

Burgess, who authored a paper on Spalding’s attack, likens the action to using a melon baller, and in so doing has forever ruined melon for me. It all happens in no more than a second or two, and just like that, the cookiecutter is gone. It’s an ambush predator of the highest order.

The creature’s lower teeth are exceedingly sharp, even for a shark, and thus excavate very clean wounds. They’ve evolved to fuse together into what looks like a white picket fence of grave bodily injury, but like any other shark, the cookiecutter will lose these in its day-to-day gougings, perhaps as often as every two weeks, according to Burgess. But waiting in that jaw are row after row of beautiful new chompers.

In addition to such handy hunting tools as electroreceptors and a good sense of smell that come with being a shark, the cookiecutter has enormous eyes and a green bioluminescent glow, suggesting the creature is primarily a nighttime hunter.

This bioluminescence comes from light-emitting organs in its skin called photophores, Burgess says. “The control over showing or not showing the light is done by use of little cells called melanophores that are sort of masking organs,” he said. “And so they use these dark-colored cells to go over the top of the light or move away from the light.” In this way the cookiecutter can flash like a strobe, perhaps to communicate with its own species.

Interestingly, though, whereas the deep-sea anglerfish attracts smaller prey with its glowing lure, the cookiecutter may use a riskier strategy: luring big predators that could easily swallow it whole, only to juke around at the last second and torpedo their flanks.

This behavior might seem … really, really dumb. But animals obviously don’t evolve to die prematurely. Genes that aid in survival get passed along. Those that don’t will end up dissolving in the stomachs of predators. So if the cookiecutter is indeed playing chicken of the sea, it’s been doing it right for a real long time. Just call it the ocean’s James Dean.

“I’ve never seen a cookiecutter in the stomach of any other animal,” said Burgess. “Which means that they’re pretty wily, and they must be pretty fast and reclusive at the same time.”

Burgess reckons that like a lot of marine creatures, the cookiecutter patrols near the surface in the evening, then retreats deeper during the day, a behavior called diel vertical migration, diel being a fancy 10-dollar word meaning 24 hours. Its hunting tactics have never been observed, apart from poor Spalding observing the hole in his leg, but Burgess notes that the cookiecutter is often associated with bioluminescent squid, which also flash flamboyantly.

“We think that probably they simply stay close to these other critters,” he said, “and wait for predators to come in who are cognizant of the flashing pattern usually meaning a good meal at the other side. And when the animal, the larger fish, comes in to grab the prey items, out from the abyss or the darkness comes the cookiecutter to make a sneak grab and bite on the side of the animals.”

It’s also widely believed that the cookiecutter may be essentially cloaking itself to mimic a smaller prey item. Seen from below, the glow of its underside matches the light filtering down from the surface, so the cookiecutter would seem to disappear — save for a non-luminescent band around its neck that makes it a dead giveaway to predators.

But despite that popular view, the collar does in fact glow, Burgess says. And he suggests that by flashing, the band may help draw would-be predators to the “business end” of the shark. Plus, attracting big nasty teeth specifically from below is probably a silly idea, as the lady from the Jaws poster would no doubt tell you if she hadn’t been eaten by a shark or was even real in the first place.

Read more at Wired Science