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 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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The velvet belly lantern shark (or simply velvet belly), Etmopterus spinax, is a species of dogfish shark in the family Etmopteridae. One of the most common deepwater sharks in the northeastern Atlantic Ocean, the velvet belly is found from Iceland and Norway to Gabon and South Africa at a depth of 70–2,490 m (230–8,170 ft). A small shark generally no more than 45 cm (18 in) long, the velvet belly is so named because its black underside is abruptly distinct from the brown coloration on the rest of its body. The body of this species is fairly stout, with a moderately long snout and tail, and very small gill slits. Like other lantern sharks, the velvet belly is bioluminescent, with light-emitting photophores forming a species-specific pattern over its flanks and abdomen. These photophores are thought to function in counter-illumination, which camouflages the shark against predators. They may also play a role in social interactions.

Young velvet bellies feed mainly on krill and small bony fish, transitioning to squid and shrimp as they grow larger. There is evidence that individuals also move into deeper water as they age. This species exhibits a number of adaptations to living in the deep sea, such as specialized T-cells and liver proteins for dealing with the higher concentrations of heavy metals found there. Velvet bellies often carry a heavy parasite load. It is ovoviviparous, giving birth to litters of 6–20 young every 2–3 years. This species has virtually no commercial value but large numbers are caught as bycatch in deepwater commercial fisheries. Although its population status has not been assessed, the heavy fishing pressure throughout its range and its slow reproductive rate are raising conservation concerns.

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... 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 "the Hurricane Shark is real"?
... 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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Credit: Didier Descouens

The jaw of a shortfin mako shark. The species feeds mainly upon cephalopods, bony fishes including mackerel, tuna, bonito, and swordfish, but it may also eat other sharks, porpoises, sea turtles, and seabirds.

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... that the taillight shark has a gland on its belly that releases clouds of luminescent blue fluid?
...that the Jersey Shore shark attacks of 1916 killed four people and inspired Peter Benchley's novel Jaws (1974)?
... that the presence of the rare bigeye sand tiger in the Pacific Ocean was first suspected based on teeth recovered from the ocean floor?
... that the rough skin of the nursehound was once used as an abrasive called "rubskin", which cost a hundred times more than sandpaper?
... that the epaulette shark can survive for an hour without oxygen?

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General images

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

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