Cookiecutter Shark (Isistius brasiliensis)

Also called the Cigar shark the Cookiecutter shark is a small squaliform shark. It is semi-tubular shaped and only grows about 50cm (~20 inches). Spending most of its life in the deep water column it is difficult to study, so not very much is known about the location or behavior of this shark. It has, however, been spotted and collects in many places world-wide. This parasitic shark uses its sharp and pointed upper teeth to latch onto the skin of a much larger marine creature (other sharks, fish, or marine mammals), using its triangular lower teeth it scoops out a piece of flesh to eat. The larger animal is then left with a decent sized hole in its skin and continues on with its life. The Cookiecutter shark often loses its teeth throughout their life in order to ensure that their teeth are sharp, large, and strong, otherwise they would not be able to feed as efficiently. This shark seems to swallow the teeth that it loses, which some scientists speculate could be a way to recycle the calcium and other materials used in tooth structure since they live in a nutrient poor environment.

They live in the open ocean and there is at least one case where a human was bit. This person was a long-distance swimmer, swimming between two islands of Hawai’i at night surrounded by boats using lights (the lights attracted prey). The swimmer was bitten on the calf, which resulted in no damage other than a decent scar.