Portal:Sharks

Portal topics: Activities; Culture; Geography; Health; History; Mathematics; Nature; People; Philosophy; Religion; Society; Technology; Random portal

Welcome to the shark portal

Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the Batoidea (rays and kin). Some sources extend the term "shark" as an informal category including extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as Cladoselache and Doliodus first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Late Ordovician (458–444 million years ago). The earliest confirmed modern sharks (selachimorphs) are known from the Early Jurassic around 200 million years ago, with the oldest known member being Agaleus, though records of true sharks may extend back as far as the Permian.

Sharks range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species that is only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 metres (40 ft) in length. They are found in all seas and are common to depths up to 2,000 metres (6,600 ft). They generally do not live in freshwater, although there are a few known exceptions, such as the bull shark and the river sharks, which can be found in both seawater and freshwater, and the Ganges shark, which lives only in freshwater. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.

Several species are apex predators, which are organisms that are at the top of their food chain. Select examples include the bull shark, tiger shark, great white shark, mako sharks, thresher sharks, and hammerhead sharks. (Full article...)

Refresh with new selections below (purge)

edit

Selected article - show another

The blacktip shark, Carcharhinus limbatus, is a species of requiem shark, family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have revealed substantial variation within this species, with populations from the western Atlantic Ocean isolated and distinct from those in the rest of its range. The blacktip shark has a stout, fusiform body with a pointed snout, long gill slits, and no ridge between the dorsal fins. Most individuals have black tips or edges on the pectoral, dorsal, pelvic, and caudal fins. It attains a maximum length of 2.8 m (9.0 ft).

Swift, energetic piscivores, blacktip sharks are known to make spinning leaps out of the water while attacking schools of small fish. Their demeanor has been described as "timid" compared to other large requiem sharks. Both juveniles and adults form groups of varying size. Like other members of its family, the blacktip shark is viviparous; females bear 1–10 pups every other year. Young blacktip sharks spend the first months of their lives in shallow nurseries, and grown females will return to the nurseries where they were born to give birth themselves. In the absence of males, females are also capable of asexual reproduction. Normally wary of humans, blacktip sharks can become aggressive in the presence of food and have been responsible for a number of attacks on people. This species is of importance to both commercial and recreational fisheries across many parts of its range, with its meat, skin, fins, and liver oil utilized. It has been assessed as Near Threatened by the World Conservation Union, on the basis of its low reproductive rate and level of human exploitation.

More selected articles

Read more...

Did you know (auto-generated)

... that "the Hurricane Shark is real"?
... that Hixxy and Sharkey created a schism in the UK rave music scene in 1995?
... that the ampullae of Lorenzini enable sharks to sense electric fields?
... that a shark cost a competitor a silver medal in the spearfishing event at the 2014 Micronesian Games?
... that Timo Meier became the first player in San Jose Sharks franchise history to score five goals in one game when he was 25?
... that Alexis Sharkey's last Instagram post before her murder documented her travels to Tulum, Mexico?

edit

Related portals

edit

WikiProjects

WikiProjects related to sharks:

edit

Selected picture - show another

Credit: Citron

The frilled shark (Chlamydoselachus anguineus) is one of two extant species of shark in the family Chlamydoselachidae, with a wide but patchy distribution in the Atlantic and Pacific Oceans.

More selected pictures

Read more...

edit

More Did you know? - show different entries

... that the milk shark is so named because of a belief in India that eating its meat improves lactation?
... that the silky shark is the most common source of ornamental shark jaws sold to tourists in the tropics?
... that the southern African frilled shark preys mainly on smaller sharks, which it swallows whole with its greatly distensible mouth?
... that more than 90 percent of the night sharks caught off northeastern Brazil contain mercury concentrations higher than that considered safe by the local government?
... that the largetooth cookiecutter shark has the largest teeth relative to its body of any living shark?

More did you know facts

General images

The following are images from various shark-related articles on Wikipedia.

Image 1A ventral dissection of a pregnant female dogshark exposing its internal gill slits and internal spiracles. (from Shark anatomy)
Image 2Dorsal fin diagram with landmarks labeled. (from Shark anatomy)
Image 3A 14-foot (4.3 m), 1,200-pound (540 kg) tiger shark caught in Kāne'ohe Bay, Oahu, in 1966
Image 4A sign at Pyramid Rock Beach in Hawaii warning about a shark sighting, 2015 (from Shark tourism)
Image 5The whale shark, the world's largest fish, is classified as Endangered.

Binding legislation and harvest management strategies... are urgently needed to address the disproportionate impact of fisheries on cartilaginous fishes.

– IUCN global study 2010

(from List of threatened sharks)
Image 6This grey reef shark demonstrates countershading, with its darker dorsal surface and lighter ventral surface. (from Shark anatomy)
Image 7The major features of sharks (from Shark anatomy)
Image 8White shark cage diving near Gansbaai in South Africa (2015) (from Shark cage diving)
Image 9Sharksucker (Echeneis naucrates) (from Shark agonistic display)
Image 10Postural elements of the agonistic display of the Gray Reef Shark (from Shark agonistic display)
Image 11Depiction of shark anatomy including eggs, pups, and the liver (from Shark anatomy)
Image 12Placoid Scale (from Shark anatomy)
Image 13The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. (from Shark anatomy)
Image 14Great white shark cages at Isla Guadalupe, Mexico (from Shark cage diving)
Image 15Branchiostoma lanceolatum (from Shark anatomy)
Image 16Clear agonistic behaviour observed in Great White Shark (from Shark agonistic display)
Image 17In a milestone decision in 2013, CITES prohibited international trade in the fins of the scalloped hammerhead (pictured) and four other shark species. (from List of threatened sharks)
Image 18Shark cage diving (from Shark tourism)
Image 19Anti-cull protesters on Perth's Cottesloe Beach in Western Australia in 2014 (from Shark culling)
Image 20Great white shark at Isla Guadalupe, Mexico, August 2006. Animal estimated at 11–12 feet (3.3 to 3.6 m) in length, age unknown. (from Shark tourism)
Image 21Postural configuration of a Gray Reef Shark as it displays agonistic behaviour, in a sculpture (from Shark agonistic display)
Image 22Shark Anatomy (50693674756) (from Shark anatomy)
Image 23Distribution of highly sensitive ampullae of Lorenzini across the shark's head and rostrum. (from Shark agonistic display)
Image 24Lateral and cross section view of shark's red and white locomotor muscles (from Shark anatomy)
Image 25A dissected view of the unique four-chambered heart of the sharkChambers: Sinus Venosus, Atrium, Ventricle, Conus Ateriosus (from Shark anatomy)
Image 26Sharks swimming outside shark-proof cage with people inside (from Shark cage diving)

edit

Topics

Shark · Outline of sharks

Shark orders

Carcharhiniformes (groundsharks) · Cladoselachiformes (extinct) · Eugeneodontida (extinct) · Heterodontiformes (bullhead sharks) · Hexanchiformes (most primitive sharks) · Hybodontiformes (extinct) · Iniopterygia (extinct) · Lamniformes (mackerel sharks) · Orectolobiformes (carpet sharks and relatives) · Pristiophoriformes (sawsharks and relatives) · Squaliformes (gulper sharks, bramble sharks, lantern sharks, rough sharks, sleeper sharks, dogfish sharks and relatives) · Squatiniformes (angel sharks) · Symmoriida (extinct) · Xenacanthida (also known as Xenacantiformes, extinct)

Major species