Portal:Sharks

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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...)

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The epaulette shark, Hemiscyllium ocellatum, is a species of longtailed carpet shark, family Hemiscylliidae, found in shallow, tropical waters off Australia and New Guinea (and possibly elsewhere). The common name of this shark comes from the very large, white-margined black spot behind each pectoral fin, which are reminiscent of military epaulettes. A small species usually under 1 m (3.3 ft) long, the epaulette shark has a slender body with a short head and broad, paddle-shaped paired fins. The caudal peduncle (to which the tail fin is attached) comprises over half the shark's length. Adults are light brown above, with scattered darker spots and indistinct saddles.

Epaulette sharks have nocturnal habits and frequent shallow water on coral reefs or in tidal pools. This shark has evolved to cope with the severe nighttime oxygen depletion (hypoxia) in isolated tidal pools by increasing the blood supply to its brain and selectively shutting down non-essential neural functions. It is capable of surviving complete anoxia for an hour without ill effects, and at a much higher temperature than most other hypoxia-tolerant animals. Rather than swim, epaulette sharks "walk" by wriggling their bodies and pushing with their paired fins. This species feeds on a wide range of small benthic invertebrates and bony fishes. Epaulette sharks are oviparous, with females depositing pairs of egg capsules around every 14 days from August to December. Due to their hardiness and small size, epaulette sharks are popular with both public and home aquaria. The World Conservation Union has assessed this species as of Least Concern, as outside of the small aquarium trade it is of little interest to fisheries.

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Did you know (auto-generated)

... that the ampullae of Lorenzini enable sharks to sense electric fields?
... that "the Hurricane Shark is real"?
... that since 2018, IKEA's stuffed toy shark Blåhaj has become a popular Internet meme and an icon of the online transgender community?
... that Hixxy and Sharkey created a schism in the UK rave music scene in 1995?
... that Alexis Sharkey's last Instagram post before her murder documented her travels to Tulum, Mexico?
... that Timo Meier became the first player in San Jose Sharks franchise history to score five goals in one game when he was 25?

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Credit: John Singleton Copley

Watson and the Shark, a 1778 oil-on-canvas painting by John Singleton Copley, depicts the rescue of Brook Watson from a shark attack in Havana, Cuba.

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... that the whitefin dogfish has light-producing organs on its upper eyelids?
... that the spinner shark is named for the spinning leaps it makes out of the water as part of its feeding strategy?
...that John Singleton Copley's painting, Watson and the Shark, was based on a real-life shark attack that occurred in Havana, Cuba in 1749?
... that, like the related cookiecutter shark, the kitefin shark sometimes feeds by taking bites out of animals larger than itself?
... that the first successful artificial insemination of a shark was performed in the cloudy catshark?

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General images

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

Image 1A sign at Pyramid Rock Beach in Hawaii warning about a shark sighting, 2015 (from Shark tourism)
Image 2This grey reef shark demonstrates countershading, with its darker dorsal surface and lighter ventral surface. (from Shark anatomy)
Image 3Shark Anatomy (50693674756) (from Shark anatomy)
Image 4A 14-foot (4.3 m), 1,200-pound (540 kg) tiger shark caught in Kāne'ohe Bay, Oahu, in 1966
Image 5Clear agonistic behaviour observed in Great White Shark (from Shark agonistic display)
Image 6The major features of sharks (from Shark anatomy)
Image 7Depiction of shark anatomy including eggs, pups, and the liver (from Shark anatomy)
Image 8White shark cage diving near Gansbaai in South Africa (2015) (from Shark cage diving)
Image 9The 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 10Sharksucker (Echeneis naucrates) (from Shark agonistic display)
Image 11Sharks swimming outside shark-proof cage with people inside (from Shark cage diving)
Image 12Distribution of highly sensitive ampullae of Lorenzini across the shark's head and rostrum. (from Shark agonistic display)
Image 13The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. (from Shark anatomy)
Image 14A ventral dissection of a pregnant female dogshark exposing its internal gill slits and internal spiracles. (from Shark anatomy)
Image 15Great 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 16Anti-cull protesters on Perth's Cottesloe Beach in Western Australia in 2014 (from Shark culling)
Image 17A dissected view of the unique four-chambered heart of the sharkChambers: Sinus Venosus, Atrium, Ventricle, Conus Ateriosus (from Shark anatomy)
Image 18Dorsal fin diagram with landmarks labeled. (from Shark anatomy)
Image 19Placoid Scale (from Shark anatomy)
Image 20Shark cage diving (from Shark tourism)
Image 21Lateral and cross section view of shark's red and white locomotor muscles (from Shark anatomy)
Image 22In 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 23Great white shark cages at Isla Guadalupe, Mexico (from Shark cage diving)
Image 24BranchiostomaLanceolatum PioM (from Shark anatomy)
Image 25Postural elements of the agonistic display of the Gray Reef Shark (from Shark agonistic display)
Image 26Postural configuration of a Gray Reef Shark as it displays agonistic behaviour, in a sculpture (from Shark agonistic display)

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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