The cookiecutter shark belongs to the sleeper shark family. In appearance, this shark resembles dogfish sharks. Because of its long, thin body structure, it is nicknamed cigar shark. The shark earns its name because it leaves a cookie shaped wound on the body of its prey. Despite being a small shark, the cookiecutter has the largest teeth compared to its overall body size of all sharks, which it uses to take round chunks out of larger marine creatures. The shark’s lower body is bioluminescent, capable of emitting greenish glow. The bioluminescent ability is because the shark’s lower body is covered in photophores, light producing organs.
Cookiecutter sharks have a wide range of habitat and are typically found in deep water environment below 3,281 ft. Although the sharks are motivated hunters and generally known to attack big marine organisms such as whales, tuna, and even sharks, yet they are believed to pose no threat to humans. Cookiecutter sharks are seldom hunted by fishermen and since they have wide distribution are categorized by ICUN as Least Concern.
Taxonomy
The cookiecutter shark has had three scientific names with the current name being Isistius brasiliensis. The genus name is derived from the Egyptian god of light ‘Isis’, while the species name refers to one place it is found, off Brazil coast.
Morphology
The sharks are relatively small. Adult cookiecutter only grows to about 16.5 inches in length, while the females can reach 22 inches in lengths. Cookiecutter sharks have a short snout, dark brown or grayish dorsal side, and a light ventral side. Around their gills, they have a dark brown band, which together with their shape gave them the nickname ‘cigar shark.” The shark has small teeth in their upper jaw and 25 to 31 triangular-shaped teeth in their lower jaw. The teeth are used along with their lips to attach to prey in a suction-like form.
Adaptation
The bioluminescence emitted from the cookiecutter sharks help them to lure bigger prey where their fearsome looking teeth enable them to attach to and cut off flesh from prey bodies. They are mostly found in deep water environment, thus making them unlikely to be caught during fishing. They have oily liver, which might assist them in adapting to deepwater environments.
Feeding
The shark is a carnivore. In most cases, cookiecutter sharks feed on much larger marine animals such as seals, whales and dolphins.
Habitat
Cookiecutter sharks can be found in the tropical waters of Atlantic, Pacific, and Indian Oceans. Cookiecutter sharks undertake migration every day, where they spend daytime in deep waters at a depth of about 3,281 ft, and at night move toward the water surface.
Reproduction
Cookiecutter sharks engage in ovoviviparous mode of reproduction. The young ones can be up to 6 to 12 per litter. The males mature when they attain 14 inches in length, and the females at 16 inches. Gestation period ranges between 12 to 22 months. Little is actually known about reproduction in cookiecutter sharks.The lifespan of the cookiecutter shark is still unknown.
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References
Bester, C (2019). Isistius brasiliensis. Cookiecutter Shark. Florida Museum. Retrieved from https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/isistius-brasiliensis/
Kennedy, J (2019, May 25). Fast Facts about Cookiecutter Sharks. ThoughtCo. Retrieved from https://www.thoughtco.com/cookie-cutter-shark-facts-2291429
Lefevre, K (2019). Cookiecutter Shark. SHARKsider. Retrieved from https://www.sharksider.com/cookiecutter-shark/
Marinebio (2019). Cookiecutter Sharks. Isistius brasiliensis. Retrieved from https://marinebio.org/species/cookiecutter-sharks/isistius-brasiliensis/
McCarthy, E (2014, June 5). 14 Facts About the Cookiecutter Shark. Mental Floss. Retrieved from http://mentalfloss.com/article/57124/14-facts-about-cookiecutter-s