Sawshark
Overview
 
The sawsharks or saw sharks are an order (Pristiophoriformes) of shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s bearing long blade-like snouts edged with teeth, which they use to slash and disable their prey. Most occur in waters from South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

 to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, at depths of 40 metres (131.2 ft) and below; in 1960 the Bahamas sawshark was discovered in the deeper waters (640 m to 915 m) of the northwestern Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

.
Sawsharks have a pair of long barbels
Barbel (anatomy)
A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...

 about halfway along the snout.
Encyclopedia
The sawsharks or saw sharks are an order (Pristiophoriformes) of shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s bearing long blade-like snouts edged with teeth, which they use to slash and disable their prey. Most occur in waters from South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

 to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, at depths of 40 metres (131.2 ft) and below; in 1960 the Bahamas sawshark was discovered in the deeper waters (640 m to 915 m) of the northwestern Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

.

Description and biology

Sawsharks have a pair of long barbels
Barbel (anatomy)
A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...

 about halfway along the snout. They have two dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

s, but lack anal fins, and range up to 170 centimetres (5.6 ft) in length. Genus Pliotrema has six gill slit
Gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...

s, and Pristiophorus the more usual five. The teeth of the saw typically alternate between large and small.

The sharks typically feed on fish, squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...

, and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s, depending on species. They cruise the bottom, using the barbels and ampullae of Lorenzini
Ampullae of Lorenzini
The ampullae of Lorenzini are special sensing organs called electroreceptors, forming a network of jelly-filled pores. They are mostly discussed as being found in cartilaginous fishes ; however, they are also reported to be found in Chondrostei such as Reedfish and sturgeon. Lungfish have also been...

 on the saw to detect prey in mud or sand, then hit victims with side-to-side swipes of the saw, crippling them.

Although they are similar in appearance, sawsharks are distinct from sawfish
Sawfish
Sawfish, also known as the Carpenter Shark, are a family of rays, characterized by a long, toothy nose extension snout. Several species can grow to approximately . The family as a whole is largely unknown and little studied...

. Sawfish have a much larger maximum size, lack barbels, have evenly sized rather than alternating sawteeth, and have gill slits on their undersurface rather than on the side of the head.

Genera and species

There are six described species of sawshark known, in two genera. The latest species, Pristiophorus delicatus, was only discovered in 2008.

Pliotrema

This genus consists of a single species, the sixgill sawshark
Sixgill sawshark
The sixgill sawshark, Pliotrema warreni, the only member of the genus Pliotrema, is a sawshark of the family Pristiophoridae, found in the subtropical waters of the western Indian Ocean between latitudes 23° S and 37° S, at depths of between 60 and 430 m. Its length is up to about...

, distinguished from Pristiophorus by having six pairs of gill slits. In addition, their rostral sawteeth have prominent transverse ridges on the basal ledges, and the large teeth have posterior serrations.
  • Pliotrema warreni Regan, 1906 (Sixgill sawshark)

Pristiophorus

Members of this genus have five gill slits. Their rostral sawteeth lack prominent transverse ridges on the basal ledges, and the large teeth are not posteriorly serrated.
  • Pristiophorus cirratus (Latham
    John Latham (ornithologist)
    John Latham was an English physician, naturalist and author. He was born at Eltham in Kent, and was the eldest son of John Latham, a surgeon there, and his mother was a descendant of the Sothebys, in Yorkshire....

    , 1794)
    (Longnose sawshark)
  • Pristiophorus delicatus Yearsley, Last & W. T. White, 2008 (Tropical sawshark)
  • Pristiophorus japonicus Günther, 1870 (Japanese sawshark)
  • Pristiophorus nancyae Ebert & Cailliet, 2011
  • Pristiophorus nudipinnis Günther, 1870 (Shortnose sawshark)
  • Pristiophorus schroederi S. Springer
    Stewart Springer
    Stewart Springer, was a world renowned expert on shark behavior, classification , and distribution of shark populations. There are more than 35 species of sharks, skates, rays, and other animals either classified originally by him or named after him.-Education:Springer was a field naturalist,...

     & Bullis, 1960
    (Bahamas sawshark)

See also


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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