Largetooth cookiecutter shark facts for kids
Quick facts for kids Largetooth cookiecutter shark |
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Isistius
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| Species: |
plutodus
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| Range of the largetooth cookiecutter shark | |
The largetooth cookiecutter shark (Isistius plutodus) is a very rare type of shark. It belongs to a group of sharks called Squaliformes. This shark lives deep in the ocean, usually between 60 and 200 meters (about 200 to 650 feet) down. It has been found in different parts of the Atlantic Ocean and Pacific Ocean.
As its name suggests, this shark looks a lot like the cookiecutter shark. But the largetooth cookiecutter shark has much bigger teeth on its lower jaw. It can grow up to 42 centimeters (about 16.5 inches) long. This shark eats by taking big bites out of larger animals. Its diet includes bony fishes, other sharks, and even marine mammals. Not much is known about its life, but it is thought to be a slower swimmer than its cousin, the cookiecutter shark.
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What is a Largetooth Cookiecutter Shark?
The largetooth cookiecutter shark was first described in 1964. Two scientists, Jack Garrick and Stewart Springer, wrote about it in a science magazine called Copeia. They studied an adult female shark that was 42 centimeters (16.5 inches) long. This shark was caught in the Gulf of Mexico, near Alabama.
The shark's scientific name, plutodus, comes from ancient Greek words. Ploutos means "wealth" or "abundance," and odous means "tooth." So, its name means "wealthy tooth" or "abundant tooth," referring to its large teeth. People sometimes call it the bigtooth or longtooth cookiecutter shark. It is also known as the Gulf dogfish.
Where Do These Sharks Live?
The largetooth cookiecutter shark is much rarer than its cousin, I. brasiliensis. Scientists have only found about ten of these sharks so far. They have been caught in a few different places around the world. These include:
- Off the coast of Alabama in the United States.
- Near Bahia in Brazil.
- Around the Azores islands.
- Off Western Sahara in the Atlantic Ocean.
- Near Okinawa and New South Wales in the Pacific Ocean.
These sharks were found in the upper part of the deep ocean, called the epipelagic zone. This is between 60 and 200 meters (about 200 to 650 feet) deep. They were caught near land, over continental shelves or continental slopes. Sometimes, they were found near very deep oceanic trenches. The reason this shark is so rare might be because it lives in a small area. Or, it might just prefer even deeper waters where we don't often look.
What Does This Shark Look Like?
The largetooth cookiecutter shark has a body shaped like a cigar. Its head and snout are very short and blunt. It has large, oval eyes that help it see with binocular vision. This means it can see with both eyes at once, like humans do. Behind its eyes are wide, angled openings called spiracles.
Its nose openings, called nostrils, are small. Each one has a small, pointed flap of skin in front of it. The shark's mouth goes straight across its face. It has deep folds at the corners and fleshy lips that can suck onto things. Its jaws are bigger and stronger than those of the regular cookiecutter shark. It has fewer rows of teeth, about 29 in the upper jaw and 19 in the lower jaw.
The upper teeth are small and narrow. They are straight in the middle of the jaw and become more angled towards the sides. The lower teeth are huge. They are the biggest teeth compared to body size of any living shark! These teeth are shaped like triangles. They have tiny jagged edges and fit together like puzzle pieces. The shark also has five tiny pairs of gill slits.
The shark has two small dorsal fins with rounded tips. They are located far back on its body. The first dorsal fin is slightly in front of its pelvic fins. The second dorsal fin is just behind the first one and is almost a third taller. Its pectoral fins are small and rounded. They are placed high on its body, behind the last gill slit. The pelvic fins are tiny, and it does not have an anal fin.
The tail fin, called the caudal fin, is very short. The top part of the tail is twice as long as the bottom part. It has a noticeable notch near the tip. The shark is a plain dark brown color. Its fins have clear edges, and its belly has scattered light-emitting spots called photophores. Some sharks of this species do not have the dark "collar" that the regular cookiecutter shark has on its throat. However, some recently caught sharks did have this collar. This suggests that the missing collar might be due to how the sharks were preserved. The biggest one ever found was 42 centimeters (16.5 inches) long.
How Does This Shark Live and Eat?
Scientists believe the largetooth cookiecutter shark is not as active as the regular cookiecutter shark. It is thought to be a weak swimmer. A large part of its body is filled with an enormous oil-filled liver. This helps the shark float in the water without much effort. Unlike the regular cookiecutter shark, this species has binocular vision. This might help it aim at its prey more accurately. We don't know much about its life cycle. It is likely that the young develop inside the mother without a placenta, similar to other sharks in its family.
Like its cousin, the largetooth cookiecutter shark is a parasite. It feeds by taking out plugs of flesh from bigger animals. The regular cookiecutter shark is thought to latch onto its prey and twist its body to make a circular wound. But the largetooth cookiecutter shark seems to use a "sweeping" bite. This creates a larger, oval-shaped wound that is twice as long as the shark's mouth. These wounds have parallel tooth marks inside.
This shark is known to bite bony fishes, other sharks, and marine mammals. One study found that the largetooth cookiecutter shark caused 80% of the cookiecutter wounds on cetaceans (like dolphins and whales) off Brazil. The side of the body was the most common place for bites. The head and belly were also often attacked. In a few cases, bites on dolphins seemed to cause them to get stuck on shore, which was very bad for them. Another animal it preys on is the subantarctic fur seal. There have been at least two cases where young seals got stuck on shore after being bitten.
Sharks and People
The largetooth cookiecutter shark does not usually affect commercial fishing. It might sometimes damage valuable fish like billfishes. Most of the sharks found have been caught by accident. This happens when fishing boats use trawl nets or longlines to catch other fish.
Because these sharks are caught so rarely, and they probably live in many different places, the International Union for Conservation of Nature (IUCN) says they are of Least Concern. This means they are not currently considered to be in danger of disappearing.
