Megamouth shark

Megamouth shark
Conservation status
Status iucn2.3 blank.svg
Data Deficient (IUCN 2.3)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Lamniformes
Family: Megachasmidae
Genus: Megachasma
Species: M. pelagios
Binomial name
Megachasma pelagios
Taylor, Compagno and Struhsaker, 1983
Range of megamouth shark (in blue)
Range of megamouth shark (in blue)

The megamouth shark, Megachasma pelagios, is an extremely rare and unusual species of deepwater shark. Discovered in 1976, only a few have ever been seen, with 42 specimens known to have been caught or sighted as of 2008 and three recordings on film. Like the basking shark and whale shark, it is a filter feeder, and swims with its enormous mouth wide open, filtering water for plankton and jellyfish. It is distinctive for its large head with rubbery lips. It is so unlike any other type of shark that it is classified in its own family Megachasmidae, though it has been suggested that it may belong in the family Cetorhinidae of which the basking shark is currently the sole member.

Contents

Physical characteristics

Little is known about the megamouth. The appearance of the megamouth is distinctive.

Body

The megamouth has a generally brownish-blackish color on top and white underneath, and an asymmetrical tail with a long upper lobe, similar to the thresher shark. The interior of its gill slits are lined with finger-like gill rakers that capture its food. A relatively poor swimmer, the megamouth has a soft, flabby body and lacks keels.

Size

Megamouths are very large sharks, able to grow to 5.5 m (18 ft) in length. Males mature by 4 m (13 ft) and females by 5 m (16 ft). Weights of up to 1,215 kg (2,679 lb) have been reported.

Mouth

Megamouth has a large mouth with small teeth, and a broad, rounded snout, causing observers to occasionally mistake megamouth for a young orca. Megamouth has luminous organs called photophores around its mouth. It is believed they may exist to lure plankton or small fish into its mouth.

Reproduction

Reproduction is ovoviviparous, whereby the animals develop in eggs that remain within the mother's body until they hatch.

Discovery

The first megamouth was captured on November 15, 1976 about 25 miles off the coast from Kaneohe, Hawaii when it became entangled in the sea anchor of a United States Navy ship. Examination of the 4.5 m (14.6 ft), 750 kg (1,650 lb) specimen by Leighton Taylor showed it to be an entirely unknown type of shark, rivaling the coelacanth as the most sensational discovery in 20th century ichthyology.

Known specimens

Main article: List of megamouth shark specimens and sightings

In the 30 years since its discovery, as of 2008 only 42 megamouth specimens have been caught or sighted. They have been found in the Pacific, Atlantic and Indian oceans. At least ten specimens have been found in the vicinity of Japan, more than any other single area. Specimens have also been pulled from the waters near Hawaii, California, Taiwan, the Philippines, Indonesia, Australia, Brazil, Senegal and Ecuador.

See also

References

External links