Cookiecutter shark

The cookiecutter shark is a small shark.

It lives in warm ocean water. This shark has a long body. It also has large eyes.

Its belly has tiny lights. These lights glow a bright green.

The lights help it hide in the water.

It has a dark neck too. This dark spot looks like a small fish.

This trick helps it catch prey.

The shark has special teeth. They work like a saw. It bites round chunks out of big fish.

These bites look like cookie shapes. This is how it got its name. It is a very neat shark.

The cookiecutter shark is a small shark with a long body.

It lives in warm ocean waters all over the world. This shark has many special ways to hunt.

Its belly is covered in photophores. These are tiny parts that make light. The lights glow a bright green. This helps the shark hide from predators below. The light matches the light coming from above.

The shark also has a dark collar around its throat. This dark spot looks like a small fish. It acts as a lure to trick other animals.

When a large animal swims near, the shark uses its lips to stick to them. It has very special teeth. The lower teeth are large and shaped like a saw.

The shark uses these teeth to cut out round plugs of flesh. These holes look like shapes made by a cookie cutter.

This is how the shark got its name. It can bite large fish and even whales. It also eats small prey like squid whole. The shark can travel in groups called schools. This helps them find food and stay safe.

The cookiecutter shark is a small, amazing creature found in warm ocean waters.

It lives in many places, like the Atlantic and Pacific Oceans. This shark is quite small, reaching only about 46 centimeters in length. Even though it is tiny, it plays a big role in the sea. It is known for a very special way of eating.

This shark can take small, round pieces of flesh from much larger animals. These marks look just like holes made by a kitchen tool. Because of this, people call it the cookiecutter shark.

To catch food, the shark uses a clever trick called subterfuge.

Its belly is covered in photophores, which are tiny organs that make light. This green light helps the shark hide from predators looking up from below. The shark also has a dark collar around its throat. This dark spot looks like the shape of a small fish.

When a larger animal swims close to this "lure," the shark strikes. It uses fleshy, suctorial lips to stick to the animal. Then, it uses its large, saw-like lower teeth to cut out a round plug of flesh.

Humans have studied these sharks for a very long time. French naturalists Jean René Constant Quoy and Joseph Paul Gaimard first described the shark. They did this during a big voyage between 1817 and 1820. They originally named it *Scymnus brasiliensis* because a specimen was caught near Brazil. Later, in 1865, an American scientist named Theodore Nicholas Gill gave it a new name. He chose the name *Isistius*, which comes from Isis, an Egyptian goddess of light.

There are many interesting facts about how this shark lives.

It performs a diel vertical migration every single day. This means it swims up toward the surface at dusk and goes deep down at dawn. During the day, it stays at depths of 1,000 meters. At night, it rises up to 350 meters. The shark has a large liver filled with oil to help it float easily. It also has very large, green eyes to help it see in the dark water.

You can think of the cookiecutter shark as a tiny master of disguise. Just like a person wearing a costume to hide, the shark uses light to blend in. It can be found near islands where large animals often gather. While it has left marks on whales, dolphins, and even submarines, it is not dangerous to humans. It is a small part of a huge, mysterious world. Many different animals, from tuna to even great white sharks, have felt its unique bite.

The cookiecutter shark, known scientifically as Isistius brasiliensis, is a small but remarkable species of shark.

It belongs to the family Dalatiidae and is often called the cigar shark due to its shape. These sharks inhabit warm, tropical, and temperate oceanic waters across the globe. They are most common in regions between 20°N and 20°S latitude. Although they are small, reaching a maximum length of only 46 centimeters, they have a massive impact on their environment. They are famous for a unique feeding method that involves taking round plugs of flesh from much larger animals. This behavior makes them a facultative ectoparasite, meaning they act like parasites but can also hunt prey entirely.

To catch food, the cookiecutter shark uses a sophisticated combination of light and shape.

Its underside is covered in photophores, which are specialized organs that produce a vivid green bioluminescence. These photophores perform counter-illumination, a process where the shark matches the light coming from above to hide its silhouette.

At the same time, a dark, non-luminescent collar around its throat acts as a lure. This collar mimics the silhouette of a small fish swimming in the water. When a larger animal approaches this perceived small fish, the shark strikes. It uses fleshy, suctorial lips to attach itself firmly to the target.

Once attached, the shark uses its specialized lower teeth to excise a neat, round chunk of flesh.

The shark's mouth is a highly specialized tool for this precise cutting. The upper jaw contains between 30 and 37 small, narrow, upright teeth. In contrast, the lower jaw has 25 to 31 much larger, broader, and knife-like teeth.

These lower teeth have smooth edges that interlock to create a single, saw-like cutting edge. This allows the shark to function like a biological bandsaw. This feeding method has left recognizable marks on a vast array of marine life. These include whales, dolphins, tuna, and even large sharks like the great white shark. Even non-living objects like submarines and undersea cables have been found with these bite marks.

The biology of the cookiecutter shark is perfectly suited for life in the deep ocean. Because it has small fins and weak muscles, it is an ambush predator that spends much of its time hovering. To stay suspended in the water without sinking, it relies on a very large liver. This liver can make up about 35% of its total body weight and is filled with low-density lipids, or oils. These oils provide neutral buoyancy, helping the shark float easily.

The shark also performs a diel vertical migration every single day. During the daylight hours, it stays at depths of approximately 1,000 meters. As dusk approaches, it rises to about 350 meters to hunt in the upper water column.

History shows that humans have been curious about this shark for a long time.

Ancient Samoan legends even spoke of fish leaving pieces of flesh as a sacrifice. Modern scientific description began with French naturalists Jean René Constant Quoy and Joseph Paul Gaimard. They described the species during an exploratory voyage between 1817 and 1820. They originally named it Scymnus brasiliensis because the specimen was caught near Brazil. In 1865, the American ichthyologist Theodore Nicholas Gill established the genus Isistius. He named the genus after Isis, the Egyptian goddess of light, likely due to the shark's glowing belly.

While the shark is famous for its bites, it is not considered a danger to humans. It is a small creature that mostly targets medium to large-sized oceanic animals. It also consumes smaller prey entirely, such as squid that are similar in size to itself.

The shark's teeth are a major biological investment. It regularly replaces its teeth, but it sheds its lower teeth in entire rows. A single shark may shed between 435 and 465 lower teeth during its lifetime. To save energy, the shark actually swallows its old teeth to recycle the calcium.

The cookiecutter shark is a vital part of the deep-sea ecosystem. It connects different layers of the ocean through its daily vertical migrations. By moving between the deep and the surface, it helps move energy through the water column. Even though it is small, its presence is felt by the largest creatures in the sea. The International Union for Conservation of Nature currently lists the species as a matter of least concern. This is because they are widely distributed and do not have much commercial value in fisheries.