Cookie cutter shark
Isistius brasiliensis
IUCN Status: Least Concern
This species only reaches up to 50 cm (1.6 ft) total length
Occasionally caught as bycatch in longlines and trawls
Found in temperate and tropical environments
This is a deepwater oceanic shark, and makes vertical migrations from 1000 m (~3000 ft) during the day to near the surface at night, and has been documented as deep as 3700 m (~12,000 ft) deep
Not much is known about its biology or population numbers
The cookie cutter is ovoviviparous, with 6-12 pups per litter that develop within the uterus and are nourished by large yolk sacs
This species leaves a characteristic, cookie-shaped, bite mark on larger fishes and marine mammals, for which this shark was given its name!
The species makes these unique bites using their suctorial lips and strong jaws to attach to the side of their prey, sink their lower teeth into the flesh, and then twist their bodies to cut out a conical chunk of flesh from their larger prey item
Their feeding behavior is aided by unique dentition, where the teeth on the upper jaws are small and thorn-like, and the teeth on the bottom jaw are much larger and triangular; the teeth along each jaw are also interconnected, so that teeth are shed all at once and replaced as a single unit
The cookie cutter shark is also bioluminescent!! They possess thousands of photophores (light-emitting organs) along the edges of their scales, that cover the entire ventral (underside) surface of their bodies, with the exception of a band lacking photophores around the throat
Bioluminescence is common in deep water organisms, and is thought to aid in camouflaging prey silhouettes from predators
