Thresher shark

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Thresher shark Temporal range: 49–0  Ma[1] PreꞒ Ꞓ O S D C P T J K Pg N Lutetian to Recent
Pelagic thresher (A. pelagicus)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Subdivision:	Selachimorpha
Order:	Lamniformes
Family:	Alopiidae Bonaparte , 1838
Genus:	Alopias Rafinesque , 1810
Type species
Alopias vulpinus Bonnaterre, 1788
Synonyms
Alopecias Müller and Henle, 1837 Alopius Swainson, 1838 Vulpecula Jarocki, 1822

Thresher sharks are large

Alopias.

All three thresher shark species have been listed as

shark-fin soup

).

Despite being active predatory fish, thresher sharks do not appear to be of threat to humans.^{[citation needed]}

Taxonomy

The genus and family name derive from the

which can be as long as the body of the shark itself.

Species

The three extant thresher shark species are all in the genus Alopias. The possible existence of a hitherto unrecognized fourth species was revealed during the course of a 1995

Phylogeny and evolution

Megachasmidae Alopiidae A. vulpinus undescribed Alopias sp. A. superciliosus A. pelagicus Cetorhinidae Lamnidae

Phylogeny of Alopiidae[4][5]

Based on

Within the family, an analysis of allozyme variation by Eitner (1995) found the common thresher is the most

Distribution and habitat

Although occasionally sighted in shallow, inshore waters, thresher sharks are primarily pelagic; they prefer the open ocean, characteristically preferring water 500 metres (1,600 ft) and less.^{[citation needed]} Common threshers tend to be more prevalent in coastal waters over continental shelves. Common thresher sharks are found along the continental shelves of North America and Asia of the North Pacific, but are rare in the Central and Western Pacific. In the warmer waters of the Central and Western Pacific, bigeye and pelagic thresher sharks are more common. A thresher shark was seen on the live video feed from one of the ROVs monitoring BP's Macondo oil well blowout in the Gulf of Mexico. This is significantly deeper than the 500 m (1,600 ft) previously thought to be their limit. A bigeye has also been found in the western Mediterranean, and so distribution may be wider than previously believed, or environmental factors may be forcing sharks to search for new territories.^[7][8]

Anatomy and appearance

Named for their exceptionally long,

, A. pelagicus, is the smallest.

Thresher sharks are fairly slender, with small

The three species can be roughly distinguished by the primary color of the dorsal surface of the body. Common threshers are dark green, bigeye threshers are brown and pelagic threshers are generally blue. Lighting conditions and water clarity can affect how any one shark appears to an observer, but the color test is generally supported when other features are examined.

Diet

The thresher shark mainly feeds on schooling pelagic fish such as bluefish, juvenile tuna and mackerel, which they are known to follow into shallow waters, as well as squid and cuttlefish.^[13] Crustaceans and occasionally seabirds are also eaten. The thresher shark stuns its prey by using its elongated tail as a whipping weapon.

Behavior

External videos
Stunning tail: Thresher sharks evolved to slap and kill their prey – NBC News
Thresher Shark Stun Prey With Tail-Slap – Live Science

Thresher sharks are solitary creatures that keep to themselves. It is known that thresher populations of the

.

Endothermy

Two species of the thresher have been identified as having a modified circulatory system that acts as a counter-current heat exchanger, which allows them to retain metabolic heat.

(family Lamnidae) have a similar homologous structure to this which is more extensively developed. This structure is a strip of red muscle along each of its flanks, which has a tight network of blood vessels that transfer metabolic heat inward towards the core of the shark, allowing it to maintain and regulate its body heat.

Reproduction

embryos

No distinct breeding season is observed by thresher sharks. Fertilization and embryonic development occur internally; this ovoviviparous or live-bearing mode of reproduction results in a small litter (usually two to four) of large well-developed pups, up to 150 cm (59 in) at birth in thintail threshers. The young fish exhaust their yolk sacs while still inside the mother, at which time they begin feasting on the mother's unfertilized eggs; this is known as oophagy.

Thresher sharks are slow to mature; males reach sexual maturity between seven and 13 years of age and females between eight and 14 years in bigeye threshers. They may live for 20 years or more.

In October 2013, the first picture of a thresher shark giving birth was taken off the coast of the Philippines.^[15]

Fisheries

Thresher sharks are classified as prized game fish in the United States and South Africa.^{[citation needed]} Common thresher sharks are the target of a popular recreational fishery off Baja, Mexico.

Status

Because of their low

See also

• Shark meat

References

• "Alopias". Integrated Taxonomic Information System. Retrieved 4 May 2006.
• Froese, Rainer and Pauly, Daniel, eds. (2011). Species of Alopias in FishBase. February 2011 version.

External links

Wikispecies has information related to Alopias.

• FishBase entry on Alopiidae