Cookiecutter shark

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The cookiecutter shark (Isistius brasiliensis), also known as the cigar shark or luminous shark, is a small rarely-seen dogfish shark.

Contents

1 Naming
2 Habitat and distribution
3 Anatomy and appearance
4 Diet
5 Reproduction
6 Importance to humans
7 See also
8 References
9 External links

Naming

It gets its name from its feeding style which often creates perfect "cookie-cutter" shaped plugs in the skin of large marine mammals and other large sharks.

Habitat and distribution

Worldwide in deep water. The cookiecutter shark has been found at depths of about 1,000 m (3,300 ft) below the surface of the ocean.

Anatomy and appearance

The cookiecutter sharks often glow green and grow up to 50 cm (20 in) long. 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 [link]. This is the only known instance whereby a bioluminescent lure is created by the absence of luminescence (contrast with anglerfish).

Diet

It 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. They are considered a parasite.

Reproduction

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

Importance to humans

Cookie cutter sharks have been known to take bites out of submarine sonar domes, causing damage to the housing.

References

Stevens (2003). [Isistius brasiliensis]. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006. Database entry includes justification for why this species is of least concern
[Isistius brasiliensis (TSN 160683)]. Integrated Taxonomic Information System. Accessed on 23 January 2006.
"[Isistius brasiliensis]." FishBase. Ed. Ranier Froese and Daniel Pauly. 09 2005 version. N.p.: FishBase, 2005.

External links

[Glow in the dark shark has killer smudge] by S. Milius
[Australian Museum Fish Site]
[Australian Museum Fish Site page 2]
[Cookie Cutter photo essay]

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