Cookiecutter shark

From Freepedia

Cookiecutter shark

Scientific classification

Kingdom:	Animalia
Subkingdom:	Deuterostomia
Phylum:	Chordata
Class:	Chondrichthyes
Order:	Squaliformes
Family:	Dalatiidae
Genus:	Isistius
Species:	I. brasiliensis

Binomial name

Isistius brasiliensis
(Quoy & Gaimard, 1824)

The Cookiecutter shark (also known as the Cigar shark or Luminous shark) is a small rarely-seen shark which often glows green and grows up to 20 inches long. It has been found at depths of about 3,300 feet below the surface of the ocean.

The Cookiecutter shark derived its name from its habit of removing small circular chunks of flesh from whales and large fish. It is hypothesized that the shark seizes its much larger prey with its jaws, then rotates its body to achieve a highly symmetrical cut.

The underside of the shark is bioluminescent, glowing a pale blue-green that matches the background light from the ocean's surface that serves as camouflage to creatures beneath it. However, a small non-luminescent patch appears black, deceiving the shark's prey, smaller predatory fish (like tuna), into thinking the shark is an even smaller fish. When the predatory fish tries to strike at the shark, the shark strikes back, scoring itself another meal [1]. This is the only known instance whereby a bioluminescent lure is created by the absence of luminescence (contrast with anglerfish).

Cookiecutter sharks reproduce through aplacental viviparity in the same way as great white sharks. Little else is known about their reproduction.