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Portal:Sharks

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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 rays. However, the term "shark" has also been used for extinct members of the subclass Elasmobranchii outside the Selachimorpha, such as Cladoselache and Xenacanthus, as well as other Chondrichthyes such as the holocephalid eugenedontidans.

Under this broader definition, the earliest known sharks date back to more than 420 million years ago. Acanthodians are often referred to as "spiny sharks"; though they are not part of Chondrichthyes proper, they are a paraphyletic assemblage leading to cartilaginous fish as a whole. Since then, sharks have diversified into over 500 species. They range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species of 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. Sharks are found in all seas and are common to depths of 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.

Well-known species such as the tiger shark, blue shark, great white shark, mako shark, thresher shark, and hammerhead shark are apex predators—organisms at the top of their underwater food chain. Many shark populations are threatened by human activities. Read more...

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Captive epaulette sharks
The epaulette shark, Hemiscyllium ocellatum, is a species of longtailed carpet shark, family Hemiscylliidae, found in shallow, tropical waters off Australia and New Guinea (and possibly elsewhere). The common name of this shark comes from the very large, white-margined black spot behind each pectoral fin, which are reminiscent of military epaulettes. A small species usually under 1 m (3.3 ft) long, the epaulette shark has a slender body with a short head and broad, paddle-shaped paired fins. The caudal peduncle (to which the tail fin is attached) comprises over half the shark's length. Adults are light brown above, with scattered darker spots and indistinct saddles.

Epaulette sharks have nocturnal habits and frequent shallow water on coral reefs or in tidal pools. This shark has evolved to cope with the severe nighttime oxygen depletion (hypoxia) in isolated tidal pools by increasing the blood supply to its brain and selectively shutting down non-essential neural functions. It is capable of surviving complete anoxia for an hour without ill effects, and at a much higher temperature than most other hypoxia-tolerant animals. Rather than swim, epaulette sharks "walk" by wriggling their bodies and pushing with their paired fins. This species feeds on a wide range of small benthic invertebrates and bony fishes. Epaulette sharks are oviparous, with females depositing pairs of egg capsules around every 14 days from August to December. Due to their hardiness and small size, epaulette sharks are popular with both public and home aquaria. The World Conservation Union has assessed this species as of Least Concern, as outside of the small aquarium trade it is of little interest to fisheries.

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Leopard shark in kelp.jpg
Credit: Matthew Field
The leopard shark is a species of houndshark found along the Pacific coast of North America from the U.S. state of Oregon to Mazatlán in Mexico.

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

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
Basking shark · Blue shark · Bull shark · Great hammerhead · Great white shark · Grey reef shark · Hammerhead shark · Megalodon · Megamouth shark · Nurse shark · Oceanic whitetip shark · Requiem shark · Scalloped hammerhead · Shortfin mako shark · Swellshark · Thresher shark · Tiger shark · Whale shark


Shark biology
Ampullae of Lorenzini · Mermaid's purses · Physical characteristics of sharks · Shark teeth · Shark threat display


Shark-human interaction
Attack (drum lines, International Shark Attack File, Jersey Shore shark attacks of 1916, list of fatal, unprovoked shark attacks in the United States, shark net, shark proof cage, shark suit, Summer of the Shark· Captivity (shark tunnel· Conservation (grey nurse shark conservation, Shark Alliance, Shark Conservation Act, Shark Trust· Fishing (International Land-Based Shark Fishing Association, land-based shark fishing· Products (shark cartilage, shark finning, shark fin soup, shark liver oil)

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