TIL: How Cookiecutter Sharks Eat Is Terrifying (Explained With Cookies) | Today I Learned
In the same way you might take a Christmas tree and stick it in dough and have perfect edges, the cookie cutter shark is able to do this with its teeth. A cookie cutter shark is sometimes known as a cigar shark because of the shape of its body. They're deep water species, and they're really creepy looking. They have large eyes, funny shaped snouts, and a mouth with triangulated teeth on the bottom and erect teeth on the top.
While it has an adorable name, it's capable of cutting perfectly cylindrical plugs of flesh out of its victims. Cookie cutter sharks spend the majority of their time at depths below 1,000 meters, so below 3,200 feet in the sea. They're extremely deep water sharks, but the interesting thing is that they come up at night to hunt.
They're successful in feeding at nighttime because they have photophores which emit bioluminescent light that mimic smaller fish. So, animals like dolphins, whales, marlins, and tuna think that these glowing lights on the cookie cutter shark are actually prey. When they come in to bite, thinking that it's a smaller fish, they find themselves in a world of hurt because the cookie cutter shark then turns around, suctions its lips and its top teeth to their body, and then spins its body ejecting a perfectly cylindrical plug of flesh.
The cookie cutter shark is the only parasitic shark in the entire animal kingdom. They are quite small; the males only get up to about 16 inches with females to about 22 inches. So, when they are attacking their prey, they really only take plugs in the way that a parasite would do, and it's quite a characteristic plug shape. In fact, they've even found some of these plugs on the heads of nuclear submarines.
Humans don't encounter them very often because during the daytime, they're generally significantly deeper than human activity. So, unless you're in the deep ocean in the middle of the night, it's probably safe to say you won't be attacked by a cookie cutter shark.