Portal:Sharks
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 oldest confirmed modern sharks (selachimorphs) are known from the Early Jurassic, about 200 million years ago, 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 shark, which can be found in both seawater and 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 tiger shark, blue shark, great white shark, mako shark, thresher shark, and hammerhead shark. (Full article...)
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Slow-moving, generally solitary predators, horn sharks hunt at night inside small home ranges and retreat to a favored shelter during the day. Their daily activity cycles are controlled by environmental light levels. Adult sharks prey mainly on hard-shelled molluscs, echinoderms, and crustaceans, which they crush between powerful jaws and molar-like teeth, while also feeding opportunistically on a wide variety of other invertebrates and small bony fishes. Juveniles prefer softer-bodied prey such as polychaete worms and sea anemones. The shark extracts its prey from the substrate using suction and, if necessary, levering motions with its body. Reproduction is oviparous, with females laying up to 24 eggs from February to April. After laying, the female picks up the auger-shaped egg cases and wedges them into crevices to protect them from predators.
Horn sharks are harmless unless harassed, and are readily maintained in captivity. They are not targeted by either commercial or recreational fisheries, though small numbers are caught as bycatch. In Mexico this species is used for food and fishmeal, and in California its spines are made into jewelry. The International Union for Conservation of Nature (IUCN) does not yet have enough information to determine the horn shark's conservation status. It faces few threats off the coast of the United States.
Did you know (auto-generated)
- ... 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 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?
- ... that the ampullae of Lorenzini enable sharks to sense electric fields?
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- ... that no more than 250 mature northern river sharks are estimated to live in the wild?
- ... that the closure of the Tethys Sea 10–14 million years ago led to the sicklefin lemon shark and the lemon shark becoming separate species?
- ... that the spined pygmy shark, dwarf lanternshark and pygmy ribbontail catshark are candidates for being the smallest shark in the world, all maturing at under 20 cm (8 in) long?
- ... that most attacks on humans by the blacktip reef shark consist of people being bitten on their legs or feet while wading in shallow water?
- ... that the egg capsule of the crested bullhead shark has paired tendrils extending up to 2 m (6.6 ft), greater than the length of the adult shark?
General images
- Shark Anatomy (50693674756) (from
- Distribution of highly sensitive ampullae of Lorenzini across the shark's head and rostrum. (from
- A ventral dissection of a pregnant female dogshark exposing its internal gill slits and internal spiracles. (from
- Depiction of shark anatomy including eggs, pups, and the liver (from
- Postural configuration of a Gray Reef Shark as it displays agonistic behaviour, in a sculpture (from
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Western Australia in 2014 (from Shark culling)Anti-cull protesters on Perth's Cottesloe Beach in
- Sharksucker (Echeneis naucrates) (from
- Postural elements of the agonistic display of the Gray Reef Shark (from
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whale shark, the world's largest fish, is classified as Endangered.The
Binding legislation and harvest management strategies... are urgently needed to address the disproportionate impact of fisheries on cartilaginous fishes.
– IUCN global study 2010
- Shark cage diving (from
- The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. (from
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Great 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)
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grey reef shark demonstrates countershading, with its darker dorsal surface and lighter ventral surface. (from Shark anatomy)This
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CITES prohibited international trade in the fins of the scalloped hammerhead (pictured) and four other shark species. (from List of threatened sharks)In a milestone decision in 2013,
- Clear agonistic behaviour observed in Great White Shark (from
- White shark cage diving near
- Dorsal fin diagram with landmarks labeled. (from
- A dissected view of the unique four-chambered heart of the sharkChambers: Sinus Venosus, Atrium, Ventricle, Conus Ateriosus (from
- BranchiostomaLanceolatum PioM (from
- The major features of sharks (from
- Placoid Scale (from
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Hawaii warning about a shark sighting, 2015 (from Shark tourism)A sign at Pyramid Rock Beach in
- Sharks swimming outside shark-proof cage with people inside (from
- A 14-foot (4.3 m), 1,200-pound (540 kg)
- Great white shark cages at Isla Guadalupe, Mexico (from
- Lateral and cross section view of shark's red and white locomotor muscles (from
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