It had been assumed that cookiecutter sharks (also known as cigar sharks) lived in the deep ocean during the day, and would swim up to feed on animals at night. These sharks live in tropical and subtropical oceans around the world, but they live in deep waters so we don't know much about them. Scientists eventually found the animal that was responsible: Isistius brasiliensis, the cookiecutter shark. The bites looked like they'd been made with a circular cookie cutter. Even the rubber-coated sensors of some submarines and underwater cables had been bitten in this odd way. If you'd like to learn more about cookiecutters and their shark family members, see the links on the next page.For many years, researchers took notice of weirdly shaped bite marks in marine animals like dolphins, whales, sea turtles, white sharks, or people. When that happens, cookiecutters actually swallow their teeth to absorb the extra calcium. Their interconnected chompers fall out as a unit like dentures. To keep them primed for attacks, cookiecutter sharks periodically lose their teeth. Fish can usually survive a cookiecutter attack, but the wound may fester or become infected. After the cookiecutter shark has taken its fill, it releases the fish. Digging its razor-sharp teeth into fish, the cookiecutter shark then spins its body around, carving out a cookie-shaped lump of meat like a wild melon baller. Once the predator goes in for the kill, the shark whips around and latches on to its opponent's flesh with the suction power from its fleshy lips. By luring the fish to come to it, the cookiecutter then has more power to bite them than if it tried to use its feeble strength to approach. Since it appears much smaller than it is, the shark attracts predator fish looking for an easy snack. Because the rest of its body is camouflaged by the bioluminescence, to other fish, it looks like the cookiecutter's body only consists of that small portion around its head and neck. But this is actually the cookiecutter shark's trump card. Fish can distinguish that non-glowing part, which may seem like an evolutionary pitfall. However, one wide stripe around the cookiecutter shark's neck does not glow. Other fish aside from cookiecutters also practice this camouflage called counterillumination. That perspective makes the luminous part of its body virtually invisible to predators. From this vantage point, the glowing belly of the cookiecutter shark looks like a spot of sunlight or moonlight shining through the water. Since the shark swims closer to the surface of the water at night, predator fish will see it from below. Some fish scientists even suspect that cookiecutter sharks have taken bites out of almost every tropical sea dweller. Think of the cookiecutter shark as the Zorro of the sea, slashing its signature marks onto foes that generally include marlin, dolphin, tuna, stingrays, seals and other sharks. The bites don't kill their hosts, but are enough to satisfy the small sharks' appetites.Ĭookiecutter sharks get their name from the almost perfectly round, cookie-shaped wound they leave on their victims. Instead, they are the only parasitic fish in the shark family that feed off hunks of flesh ripped out of larger fish. On the top, 30 to 37 teeth stretch across like a set of dentures, and 25 to 31 larger ones extend along the bottom.Įquipped with weak fins and a puny body, cookiecutter sharks wouldn't make successful predators. Surrounded by relatively large, flabby lips, the cookiecutter's mouth houses a formidable set of pearly whites. ![]() ![]() ![]() ![]() As soon as you see a cookiecutter shark's smile, you immediately understand how it upholds the shark family reputation associated with ferocious hunting. But the diminutive name and size belie this shark's bite.
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