DailyCelestialChallenge Tuesday - AnimalKingdom - Great White Shark
The great white shark (Carcharodon carcharias) is a species of lamniform cartilaginous fish of the Lamnidae family found in the warm, temperate waters of almost all oceans. This species is the only one that survives at present of the Carcharodon genus.
White sharks are characterized by their fusiform body and great robustness, in contrast to the squashed forms that other sharks often wear. The nose is conical, short and thick. The mouth, very large and rounded, is shaped like an arch. It remains always ajar, revealing at least one row of teeth from the upper jaw and one or two from the lower one, while the water penetrates into it and continuously exits through the gills. If this flow stopped, the shark would drown because it lacked operculums to regulate the correct passage of water, and would sink into it, since not having any swim bladder is condemned to be in continuous movement to avoid it.
During the attack, the jaws open to such an extent that the shape of the head is deformed because the jaw is detached from his head, and then closed with a force 300 times greater than that of a human jaw.
The teeth are large, serrated, triangular in shape and very wide. Unlike other sharks, they have no diastema or reduction of any tooth, but have the entire jaw provided with teeth aligned and equally capable of grasping, cutting and tearing. Behind the two rows of primary teeth, white sharks have two or three more in continuous growth that replace the frequent fall of teeth with new ones and are replaced by new rows over the years. The base of the tooth has no root and is bifurcated, giving it an unmistakable appearance in the shape of an arrowhead.
The nostrils (nostrils) are very narrow, while the eyes are small, circular and completely black. On the sides are five gill slits, two pectoral fins well developed and triangular and two, near the caudal fin, much smaller. The caudal is very developed, like the great dorsal fin of its back, unmistakably for anyone. Two other small fins (second dorsal and anal) near the tail, complete the appearance of this animal.
Despite its name, the silky shark is only white in its ventral part, while the dorsal is gray and bluish.
This pattern, common in many aquatic animals, serves to be confused with sunlight (if viewed from below) or with dark marine waters (if done from above), constituting a camouflage as simple as effective. The end of the ventral part of the scapular fins and the armpit area appear stained black. The skin, very rough, consists of hard scales called dermal denticles because of its sharp shape.
However, the name "white shark" could have its logic in the case of albino specimens of this species that, although they are very rare, exist. In 1996 a young female of just 145 cm was caught off the coast of the Eastern Cape (South Africa), exhibiting this rare characteristic
Size
The most frequent length among adult white sharks is 4 to 5.5 m (males being smaller than females), although cases of exceptional individuals have been cited that widely exceeded these measures. At present it is not possible to assure which is really the maximum size in this species, fact that is reinforced by the existence of old and unreliable notes on really gigantic animals. Several of these cases are analyzed in the book The Great White Shark (1991) by Richard Ellis and John E. McCosker, both experts in sharks.
For decades, many reference books in the field of ichthyology, as well as the Guinness Book of World Records collected two white sharks as the largest ever caught; one of them was an 11 m specimen supposedly caught in the waters of South Australia, near Port Fairy, in the 1870s and the other was an 11.3 m individual caught in a herring network in New Brunswick, Canada in the 1930s.
Under this maximum length, sightings of white sharks from 7 to 10 m in length were considered to some extent common and accepted without much discussion. However, several researchers questioned the reliability of the Port Fairy report, emphasizing the large difference in size between this individual and any of the other captured white sharks. A century after the capture, the jaws of the animal, still preserved, were studied and it could be determined that its authentic body size was around 5 meters long. The confusion could be the product of a typographical failure, an error derived from the passage of Anglo-Saxon units to international (5 m is about 16.5 feet) or a simple exaggeration. Regarding the example of New Brunswick, experts believe today that it must have been a peregrine shark (Cetorhinus maximus), a species with a body similar to that of the white shark and which is common in Canadian waters.
Feeding
White sharks differ from being simple "killing machines", as the popular image (urban legend) of them holds. To capture the large marine mammals that form the basis of the diet of adults, white sharks practice an ambush characteristic: they are located several meters below the prey, which swims on or near the surface, using the dark color of its back as camouflage with the background and thus becoming invisible to its victims. When the moment arrives to attack, they advance quickly upwards with powerful movements of the tail and open the jaws. The impact usually arrives in the belly, where the shark clings tightly to the victim: if this one is small, like a sea lion, it kills it in the act and later it engulfs it whole. If it is bigger, it starts a large piece of the same that ingests whole, since its teeth do not allow it to chew. The prey can then be dead or dying, and the shark will feed again by tearing one piece after another. Excited by the presence of blood, the area will soon be filled with other sharks. In some areas of the Pacific, white sharks lash out so hard at seals and sea lions that they rise a couple of meters above water level with their prey between their jaws, before diving again. However, in the Mediterranean Sea and Atlantic coast of Africa and Europe, the white shark, like the orca and the mako, do not usually attack or feed on manifers like seals or dolphins, the attacks of white shark on man in the Mediterranean they are strange, far from the coast and deep, maybe it is because of the feeding habits based mainly on bluefin tuna, which is much more nutritious for both the white shark and the orca or mako shark.
Most attacks occur during sunrise or sunset. It is at this moment when the depths can not be adequately glimpsed. Only the surface is appreciated, because the rays of the sun at that time are still weak to penetrate the depths. For what it provides an advantage to the shark to attack its prey without being perceived.
This species also consumes carrion, especially the one that comes from whale carcasses drifting from those that pull large pieces. Near the coasts, white sharks consume large quantities of floating objects by mistake: in their stomachs they have even found car license plates.
Both the hunting and the rest of the life of the great white shark are usually solitary. Occasionally couples or small groups are seen moving to the search for food, a task that leads them to travel hundreds of kilometers. Although preferably nomads, some specimens prefer to feed in certain coastal areas, as occurs in some regions of California, South Africa and especially Australia.
The legendary great white shark is much more fearsome in our imagination than in reality. As the scientific investigation of these elusive predators increases, their image as a savage killing machine begins to fade.
Of the one hundred or more shark attacks registered annually worldwide, between a third and a half are attributable to the white shark. However, most are not fatal, and new studies show that white sharks, curious by nature, are trying a bite to then let go of their victims, instead of trying to devour humans. This distinction may offer poor comfort, but it shows that humans are not part of the white shark's menu.
The white shark is the largest predatory fish on Earth. On average, they measure around 4.5 meters, although specimens exceeding 6 meters in length and 2.250 kilograms in weight have been registered.
The upper part of the body is slate gray to merge with the seabed of rocky shores, but they owe their name to the universally white color of their belly. They are swimmers with aerodynamic torpedo shape and have powerful tails that allow them to travel at speeds of up to 25 kilometers per hour. They can even get out of the water completely, emerging as whales when attacking their prey from below.
These predators, highly adapted, have up to 300 triangular teeth in the shape of a saw, arranged in several rows, and an exceptional sense of smell with which they detect their prey. They even have organs that perceive the tiny electromagnetic fields generated by animals. They feed mainly on sea lions, seals, small toothed whales and even sea turtles, as well as carriages.
They are present in temperate coastal waters of the whole world. There are no reliable data on the population of white shark. However, scientists agree that their numbers are falling rapidly due to overfishing and accidental catches with gillnets, among other factors, and are on the list of endangered species.
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