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 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 milk shark, Rhizoprionodon acutus, is a species of requiem shark, family Carcharhinidae, whose common name comes from an Indian belief that consumption of its meat promotes lactation. The largest and most widely distributed member of its genus, the milk shark typically measures 1.1 m (3.6 ft) long and can be found in coastal tropical waters throughout the eastern Atlantic and the Indo-Pacific regions. Occurring from the surface to a depth of 200 m (660 ft), this species is common near beaches and in estuaries, and has been recorded swimming up rivers in Cambodia. Juveniles are known to inhabit tidal pools and seagrass meadows. The milk shark has a slender body with a long, pointed snout and large eyes, and is a nondescript gray above and white below. This shark can be distinguished from similar species in its range by the long furrows at the corners of its mouth, and 7–15 enlarged pores just above them.

Among the most abundant sharks within its range, the milk shark feeds primarily on small bony fishes but also takes cephalopods and crustaceans. In turn, it often falls prey to larger sharks and possibly marine mammals. In common with other members of its family, this species is viviparous with the developing embryos sustained by a placental connection. Females give birth to 1–8 young either during a defined breeding season or throughout the year, depending on location. The reproductive cycle is usually annual but may be biennial or triennial. Large numbers of milk sharks are caught by artisanal and commercial fisheries in many countries for meat, fins, and fishmeal. Despite this, the International Union for Conservation of Nature (IUCN) has assessed this species as being of Least Concern, because its wide distribution and relatively high productivity seemingly allow present levels of exploitation to be sustained.

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... 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 shark fin is one of the "four sea delicacies", a quartet of luxury seafoods in Chinese cuisine?
... that, during Real Madrid's 1927 tour of the Americas, José María Muñagorri nearly jumped into shark-infested waters to rescue a teammate?
... that a shark cost a competitor a silver medal in the spearfishing event at the 2014 Micronesian Games?
... that the parasitic copepod Driocephalus cerebrinoxius burrows into the brains of sharks through their noses?

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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 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 1Clear agonistic behaviour observed in Great White Shark (from Shark agonistic display)
Image 2Distribution of highly sensitive ampullae of Lorenzini across the shark's head and rostrum. (from Shark agonistic display)
Image 3Postural elements of the agonistic display of the Gray Reef Shark (from Shark agonistic display)
Image 4Branchiostoma lanceolatum (from Shark anatomy)
Image 5In 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 6Shark cage diving (from Shark tourism)
Image 7Lateral and cross section view of shark's red and white locomotor muscles (from Shark anatomy)
Image 8Postural configuration of a Gray Reef Shark as it displays agonistic behaviour, in a sculpture (from Shark agonistic display)
Image 9Great 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 10Great white shark cages at Isla Guadalupe, Mexico (from Shark cage diving)
Image 11The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. (from Shark anatomy)
Image 12This grey reef shark demonstrates countershading, with its darker dorsal surface and lighter ventral surface. (from Shark anatomy)
Image 13The 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 14White shark cage diving near Gansbaai in South Africa (2015) (from Shark cage diving)
Image 15Dorsal fin diagram with landmarks labeled. (from Shark anatomy)
Image 16Sharksucker (Echeneis naucrates) (from Shark agonistic display)
Image 17A ventral dissection of a pregnant female dogshark exposing its internal gill slits and internal spiracles. (from Shark anatomy)
Image 18The major features of sharks (from Shark anatomy)
Image 19Placoid Scale (from Shark anatomy)
Image 20A dissected view of the unique four-chambered heart of the sharkChambers: Sinus Venosus, Atrium, Ventricle, Conus Ateriosus (from Shark anatomy)
Image 21Depiction of shark anatomy including eggs, pups, and the liver (from Shark anatomy)
Image 22Shark Anatomy (50693674756) (from Shark anatomy)
Image 23In 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 24Sharks swimming outside shark-proof cage with people inside (from Shark cage diving)
Image 25Anti-cull protesters on Perth's Cottesloe Beach in Western Australia in 2014 (from Shark culling)
Image 26A sign at Pyramid Rock Beach in Hawaii warning about a shark sighting, 2015 (from Shark tourism)
Image 27A 14-foot (4.3 m), 1,200-pound (540 kg) tiger shark caught in Kāne'ohe Bay, Oahu, in 1966

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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