Portal:Sharks

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Sharks are a group of elasmobranch cartilaginous fishes characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the division Selachii and are the sister group to the Batomorphi (rays and skates). 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 (Selachii) 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) to 18.8 metres (62 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 placoid scales (denticles) that protects the skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.

Several shark species are apex predators, which are organisms that are at the top of their food chain with select examples including the bull shark, tiger shark, great white shark, mako sharks, thresher sharks, greenland sharks and hammerhead sharks. Some sharks are filter-feeding planktivores, such as the whale shark and basking shark, which are among the largest fish that ever lived. (Full article...)

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The blacknose shark, Carcharhinus acronotus, is a species of requiem shark, family Carcharhinidae, common in the tropical and subtropical waters of the western Atlantic Ocean. This species generally inhabits coastal seagrass, sand, or rubble habitats, with adults preferring deeper water than juveniles. A small shark typically measuring 1.3 m (4.1 ft) long, the blacknose shark has a typical streamlined "requiem shark" shape with a long rounded snout, large eyes, and a small first dorsal fin. Its common name comes from a characteristic black blotch on the tip of its snout, though this may be indistinct in older individuals.

Blacknose sharks feed primarily on small bony fishes and cephalopods, and in turn fall prey to larger sharks. Like other members of their family, they exhibit a viviparous mode of reproduction in which the developing embryos are sustained by a placental connection. The females give birth to 3–6 young in late spring or early summer either annually or biennually, after a gestation period of 8–11 months. This species is not known to attack humans, though it has been documented performing a threat display towards divers. It is of moderate commercial and recreational importance. The conservation status of this species has not been assessed by the International Union for Conservation of Nature (IUCN); in 2009, the US National Oceanic and Atmospheric Administration (NOAA) announced that populations of the blacknose shark off the United States are being overfished, and proposed new conservation measures.

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... that the shark god Kāneikokala, according to Hawaiian tradition, rescued shipwrecked sailors and returned them to their home islands?
... that Japanese businessman Yasuyoshi Kato used embezzled funds to support his wife, who bought twenty Arabian horses, several emus, llamas, potbellied pigs, miniature cattle, and nurse sharks?
... that, during Real Madrid's 1927 tour of the Americas, José María Muñagorri nearly jumped into shark-infested waters to rescue a teammate?
... that the parasitic copepod Driocephalus cerebrinoxius burrows into the brains of sharks through their noses?
... that a shark cost a competitor a silver medal in the spearfishing event at the 2014 Micronesian Games?
... that Shark Tank was adapted from a Japanese show that aimed to encourage entrepreneurship during a lengthy period of economic stagnation in the Japanese economy?

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Credit: Terry Goss

The great white shark is an exceptionally large lamniform shark found in coastal surface waters in all major oceans.

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... that the zebra shark is striped when young and spotted when mature?
... that the blurred and smooth lanternsharks form a species group distinguished from the rest of their family by the shape and arrangement of their dermal denticles?
... that the leopard shark feeds on anchovies by swimming into their schools with its mouth open and waiting for them to accidentally enter?
... that relative to its body size, the horn shark has the strongest known bite of any shark?
... that the title for Peter Benchley's best-selling 1974 novel Jaws was not agreed until 20 minutes before it went into production?

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General images

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

Image 1Great white shark cages at Isla Guadalupe, Mexico (from Shark cage diving)
Image 2The 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 3Clear agonistic behaviour observed in Great White Shark (from Shark agonistic display)
Image 4This grey reef shark demonstrates countershading, with its darker dorsal surface and lighter ventral surface. (from Shark anatomy)
Image 5Sharksucker (Echeneis naucrates) (from Shark agonistic display)
Image 6A 14-foot (4.3 m), 1,200-pound (540 kg) tiger shark caught in Kāne'ohe Bay, Oahu, in 1966
Image 7A sign at Pyramid Rock Beach in Hawaii warning about a shark sighting, 2015 (from Shark tourism)
Image 8Shark cage diving (from Shark tourism)
Image 9Depiction of shark anatomy including eggs, pups, and the liver (from Shark anatomy)
Image 10White shark cage diving near Gansbaai in South Africa (2015) (from Shark cage diving)
Image 11Sharks swimming outside shark-proof cage with people inside (from Shark cage diving)
Image 12The major features of sharks (from Shark anatomy)
Image 13The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. (from Shark anatomy)
Image 14Distribution of highly sensitive ampullae of Lorenzini across the shark's head and rostrum. (from Shark agonistic display)
Image 15Dorsal fin diagram with landmarks labeled. (from Shark anatomy)
Image 16Anti-cull protesters on Perth's Cottesloe Beach in Western Australia in 2014 (from Shark culling)
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 18In this drawing, there is a diagram of the placement of shark organs. From this model, we can see and distinguish the placement of organs compared with other species. EX. The testes of a shark are located on the ventral plane, near the fins, while a human's testes are located further down, near the bladder. (from Shark anatomy)
Image 19Great 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 20Branchiostoma lanceolatum (from Shark anatomy)
Image 21Shark Anatomy (50693674756) (from Shark anatomy)
Image 22A dissected view of the unique four-chambered heart of the sharkChambers: Sinus Venosus, Atrium, Ventricle, Conus Ateriosus (from Shark anatomy)
Image 23Postural configuration of a Gray Reef Shark as it displays agonistic behaviour, in a sculpture (from Shark agonistic display)
Image 24Placoid Scale (from Shark anatomy)
Image 25A ventral dissection of a pregnant female dogshark exposing its internal gill slits and internal spiracles. (from Shark anatomy)
Image 26Lateral and cross section view of shark's red and white locomotor muscles (from Shark anatomy)
Image 27Postural elements of the agonistic display of the Gray Reef Shark (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