Portal:Sharks

Welcome to the shark portal

Sharks are a group of elasmobranch cartilaginous fish 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 (or Selachimorpha) and are the sister group to the Batoidea (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 (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 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 ever lived. (Full article...)

Refresh with new selections below (purge)

edit

Selected article - show another

The zebra shark, Stegostoma fasciatum (or varium), is a species of carpet shark and the sole member of the family Stegostomatidae. It is found throughout the tropical Indo-Pacific, frequenting coral reefs and sandy flats to a depth of 62 m (210 ft). Adult zebra sharks are distinctive in appearance, with five longitudinal ridges on a cylindrical body, a low caudal fin comprising nearly half the total length, and a pattern of dark spots on a pale background. Young zebra sharks under 50–90 cm (20–35 in) long have a completely different pattern, consisting of light vertical stripes on a brown background, and lack the ridges. This species attains a length of 2.5 m (8.2 ft).

Zebra sharks are nocturnal and spend most of the day resting motionless on the sea floor. At night, they actively hunt for molluscs, crustaceans, small bony fishes, and possibly sea snakes inside holes and crevices in the reef. Though solitary for most of the year, they form large seasonal aggregations. The zebra shark is oviparous: females produce several dozen large egg capsules, which she anchors to underwater structures via adhesive tendrils. Innocuous to humans and hardy in captivity, zebra sharks are popular subjects of ecotourism dives and public aquaria. The World Conservation Union has assessed this species as Vulnerable worldwide, as it is taken by commercial fisheries across most of its range (except off Australia) for meat, fins, and liver oil. There is evidence that its numbers are dwindling.

More selected articles

Read more...

Did you know (auto-generated)

... that a shark cost a competitor a silver medal in the spearfishing event at the 2014 Micronesian Games?
... 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 Hixxy and Sharkey created a schism in the UK rave music scene in 1995?

edit

Related portals

edit

WikiProjects

WikiProjects related to sharks:

edit

Selected picture - show another

Credit: Luc Viatour

The blacktip reef shark is a species of requiem shark, family Carcharhinidae, easily identified by the prominent black tips on its fins. It is among the most abundant sharks inhabiting the tropical coral reefs of the Indian and Pacific Oceans, and prefers shallow, inshore waters.

More selected pictures

Read more...

edit

More Did you know? - show different entries

... 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?

More did you know facts

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

edit

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