- More generally, "cookiecutter sharks" may refer to the entire genus Isistius.
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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.
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Anatomy and morphology
Cookiecutters are small (about 50 centimetres (20 in)) sharks with a cigar shaped body. It has large eyes with green pupils, and prominent teeth on the lower jaw used for feeding. The upper jaw of the shark consists of small teeth. In addition to the sharp teeth, the cookiecutter shark bears rather fleshy lips. The creature has 2 small dorsal fins located toward the tail. 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, earning itself another meal.[1] This is the only known instance whereby a bioluminescent lure is created by the absence of luminescence (contrast with anglerfish).
Ecology and life history
Feeding ecology
The cookiecutter shark derives its name from the shape of the bitemarks it makes in its prey. It removes small circular plugs (like cookie cutters) of flesh and skin from cetaceans such as whales and seals, and large fish, including other sharks. It is hypothesized that the shark attaches to its much larger prey with its suctorial lips and modified pharynx, (see photo[2]) then rotates its body to achieve a round, symmetrical cut. They are considered parasites, with hosts such as the Megamouth shark.[2]
Diet consists almost solely of skin, blubber and flesh, with very little calcium. To compensate, when its worn teeth are ready to be replaced the shark digests them for their calcium. In other sharks, the teeth normally fall out of the mouth onto the seabed.[3]
Distribution
The cookiecutter shark is not restricted to any area, but lives in deep water. It has been found at depths of about 1,000 metres (3,300 ft).
Interaction with humans
There has been little direct interaction between humans and the cookiecutter shark. One exception is that Maui resident Mike Spalding was reportedly bitten by a cookie-cutter shark while attempting to swim across Alenuihaha Channel in March of 2009.[4]
However, cookiecutters do occasionally mistake manmade objects for prey. Cookiecutters made damaging cuts on the neoprene boots of AN/BQR-19 hydrophone arrays located on a retractable mast in the sail of some United States Navy submarines. The arrays were later protected with fiberglass covers.[5] Another animal took a bite out of a submarine's rubber sonar dome, forcing the submarine out of service until the rubber could be replaced.[6] Cookiecutter bites have been observed in undersea electrical cables.[4]
See also
Bibliography
- Stevens (2003). Isistius brasiliensis. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. 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. Retrieved on 23 January 2006.
- "Isistius brasiliensis". FishBase. Ed. Ranier Froese and Daniel Pauly. 09 2005 version. N.p.: FishBase, 2005.
References
- ^ Glow-in-the-dark shark has killer smudge: dark patch on cookiecutter shark attracts prey. Science News (August 1, 1998) by Susan Milius [1]
- ^ a b Carol Martins & Craig Knickle. "Megamouth Shark- Parasites". Florida Museum of Natural History. http://www.flmnh.ufl.edu/fish/Gallery/descript/Megamouth/megamouth.htm. Retrieved 2009-02-09.
- ^ Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press.
- ^ a b http://www.mauinews.com/page/content.detail/id/516284.html?nav=10
- ^ Johnson, C. Scott "Sea Creatures and the Problem of Equipment Damage" United States Naval Institute Proceedings August 1978 p.106
- ^ Animal Planet's The Most Extreme episode on "The Most Extreme: Biters" on 2002-11-02 featured a segment citing this incident.[2]
External links
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