The cookie-shaped divot is probably the result of a bite from a Cookie-cutter Shark. The grooves left by the teeth are clearly visible. Danger to humans In their paper see references, below , Honebrink and colleagues describe the first documented attack on a live human by a Cookiecutter Shark. References Compagno, L. FAO species catalogue. An annotated and illustrated catalogue of shark species known to date.
Part 1 - Hexanchiformes to Lamniformes: viii, Gadig, O. First report on embryos of Isistius brasiliensis. Journal of Fish Biology. Honebrink, R. Pacific Science. Last, P. Sharks and Rays of Australia. McGrouther, M. Relative to its body size, the cookiecutter has the largest teeth of all sharks.
It uses them to take round chunks out of larger marine creatures — their trademark bites can be seen on large fish and whales of the deep ocean. When the teeth of this critter are shed, they are sometimes swallowed and digested.
Having a fortified skeleton might be helpful for the deep diving this species does. The cookiecutter shark also has an oily liver that is larger compared the liver of similar sharks, which might also aid them in swimming to greater depths. The genus name Isistius is in honor of the Egyptian goddess of light, Isis. Why might that be, you ask? The entire lower surface of the body except for the darker throat is bioluminescent , being able to emit a greenish glow.
It is covered in tiny light-producing organs called photophores. The cookiecutter is a wide-ranging pelagic shark that lives in the temperate and tropical waters of the Atlantic and Pacific Oceans, around the globe. It is often found close to islands: this could be because there is a higher concentration of prey, for better mating opportunities, or because areas around islands provide ideal nursery habitat. All of these possibilities have been suggested but no evidence is available to distinguish among them.
These fish are typically found in deep water below 3, feet m in the daytime, but have been recorded to depths of 3. At night, cookiecutter sharks move closer to the surface to feed, but they still stay at least 90 m ft deep. As soon as you see a cookiecutter shark's smile, you immediately understand how it upholds the shark family reputation associated with ferocious hunting.
Surrounded by relatively large, flabby lips, the cookiecutter's mouth houses a formidable set of pearly whites. On the top, 30 to 37 teeth stretch across like a set of dentures, and 25 to 31 larger ones extend along the bottom.
Equipped with weak fins and a puny body, cookiecutter sharks wouldn't make successful predators. Instead, they are the only parasitic fish in the shark family that feed off hunks of flesh ripped out of larger fish [source: Parker ]. The bites don't kill their hosts, but are enough to satisfy the small sharks' appetites. Cookiecutter sharks get their name from the almost perfectly round, cookie-shaped wound they leave on their victims.
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 [source: Florida Museum of Natural History ]. Some fish scientists even suspect that cookiecutter sharks have taken bites out of almost every tropical sea dweller [source: ReefQuest Centre for Shark Research ]. Cookiecutter sharks are one of many species of bioluminescent fish in the sea.
Bioluminescence means their bodies glow. Among sharks, cookiecutters glow the brightest [source: Parker ]. In fact, its scientific name Isistius brasiliensis comes from the Greek goddess Isis, the goddess of light [source: ReefQuest Centre for Shark Research ]. Bioluminescence occurs in cookiecutter sharks because of the presence of photopores glands , particularly concentrated on its lower belly.
These glands produce an enzyme called luciferose that converts chemical energy to light energy, causing the glow. Transparent cells surrounding the glands also allow the light to shine through the cookiecutter shark's skin [source: Parker ]. It gets its common name from its feeding strategy of biting off small chunks of much larger animals see more below.
This species is small and lives much of its life in the deep water column mesopelagic. It is therefore difficult to study, so there is little known about exactly where it lives, but it has been collected or observed in many places around the world, most significantly in tropical to temperate latitudes.
The cookiecutter shark is a parasite, meaning it feeds off larger animals, without killing them. It uses its sharp, pointed upper teeth to latch on the skin of a much larger shark, bony fish, or marine mammal and its thick, strong, triangular lower teeth to scoop out a mouth-sized chunk of flesh or blubber.
Several species — including bluefin tuna , great white sharks , spinner dolphins , and other large predators — have been observed with one or more scars caused by these sharks. Like all sharks, cookiecutter sharks lose several sets of teeth throughout their lifetimes. This process ensures that they always have sharp, healthy teeth capable of feeding by their preferred strategy.
0コメント