Shark - fish predators, dangerous and aggressive inhabitants of the ocean, the oldest known animals.So it accepted and it is believed by millions of people, deriving knowledge about these unique creatures of the Hollywood thriller-horror stories.Let us examine what we know about these amazing creatures that appeared much earlier than all the world's civilizations and perfectly adapted to modern life.What is a shark?It is a fish or a mammal?
Amazing fish
All scientific and encyclopedias claim that sharks - cartilaginous fishes, t. E. In the body they have absolutely no bone tissue, which is very different from their modern counterparts of habitat.However, the lack of gill covers, and structural features of the scales, cartilage ostyak indicates a primitive kind of organization, but rather on its ancient origins: it is known that 400 million years ago, these fish have sailed the world's oceans.Despite this, the sharks are one of the most advanced species of predatory ocean fish.For a long time adapting to a constantly changing environment, they are perfectly adapted and now get along well with the modern bony fishes and marine mammals, are not giving them any rate, no skill, no hunting skills.The list of more than 400 shark species, polar differ from the finest deep water, barely grow to 17-20 cm, to the giant - the whale shark, a huge 20-meter multi-ton animal.
An important difference from the bony fish are and how to reproduce.Some shark species - viviparous, t. E. Give birth to live young.Some lay eggs, protected by thick cornea.Not all the secrets of their lives are open: there are species secrets of reproduction which are still an enigma.Therefore, it is often the question arises: "Shark - it is a fish or a mammal?"
Features kind
cartilaginous skeleton and a lack of bone - the main features of the relationship of these fish to a group of animals of the primitive organization.But, as mentioned above, this did not prevent shark inhabit virtually all the oceans of the planet, long been the glory of the most dangerous and aggressive predator.Besides, nature has taken care of the protection of this wonderful animal.It's hard to find something more to defend, than scales, which has a shark.Located from head to tail, touch it resembles satin coating, but it is not necessary to carry out his hand in the opposite direction - from tail to head: vopyutsya sharp teeth into the skin.Coarse sandpaper compared with this perfect protection - a faint resemblance.
Consider device scales.Each scale is equipped with a cartilaginous fish with a small thorn rearward tip.On top of the spike is firmly covered with a layer of enamel, and its expanding base of adherent to the skin of the fish.In this cavity there are blood vessels outgrowth and nerve branches.The amount of scales on the body of fish is different: the head is the most major, mouth shark spines somewhat transformed, no longer protected by the skin and become a sharp and extremely dangerous weapon attacks - magnificent teeth.
main weapon
As modified scales, shark teeth are arranged in a strict staggered in several rows.Over the life of a predator teeth grow constantly, and the abrasion of one row sprout new, located in the back of the mouth.Serve shark teeth to chew food.It does not know how to do it.Their main purpose - to hold the prey, to break it into pieces, to swallow without interference.Different species of sharks teeth a different form, which is dictated by the special way of life.Bottom feeding on crustaceans in a solid shell organisms have flat teeth with a ribbed surface that can crush the lime protection.Fish predators have long, sharp teeth to snap a moving prey, or wide with a serrated edge, designed for tearing meat of the victim.At planktonic sharks need to have practically no teeth, they have these types of small, barely reaching 3-5 mm.
Another feature of cartilaginous fish - no gill covers.Their role is played by 5-7 gill slits located behind the head, the number of which is determined by the views of sharks, and the presence of a distinctive feature.However, all fish these predators to obtain oxygen from the water is passed through its gills.The presence of the respiratory system, characteristic for water, giving an exhaustive answer to the question: "Shark - it is a fish or a mammal?"
amazing abilities: the sense of smell, elektroretseptorny unit and the lateral line
overestimate the possibility of sharks smelling impossible.This is one of the most advanced basic sensory systems.Experiments have shown not only high sensitivity to smells of fish, and truly amazing.The shark can catch the scent of blood diluted in water in a ratio of 1: 1,000,000, and constantly uses the sense of smell when searching for partners for production or breeding in the breeding season.In the definition of the object is likely but highly olfactory involved are other organs and systems: hearing, taste buds, and the lateral line on the surface of the fish's body, able to feel how small the weak mechanical movements, and the smallest low-frequency vibrations in the waterand plays an important role in hunting, communicating with fellow and orientation.
There is unproven scientific assumptions about the ability of predators to capture odors, distributed over the air, what prompted researchers strange behavior of white sharks.She often picks up the face above the water surface, as if sniffing.
scientifically proven unique ability to detect the shark victim of her movements created by respiratory and cardiac muscles, electric fields with a negligible voltage.Long-term observation of the migration of some species at a sufficiently long distance in a straight line revealed the possibility of their orientation in the magnetic field of the Earth.
Vision
uniqueness of the fauna once again emphasizes the special structure of the eye, providing both protection from external stimuli, and excellent visual acuity.Features of the device body of the shark is the presence of blinking century, closes his eyes at the moment of the attack on the victim, thus protecting it from damage.In fairness, it should be noted that not all types have eyelids.These individuals during the attack on the victim roll their eyes.
Moreover, sharks eye has a special reflective layer located behind the retina, enhances the sensitivity of the body and greatly increases visual acuity, even in low light.Today, it does not require proof of the fact that the vision of some species of these fish many times greater than the human.
Reproduction sharks
Unlike most bony fishes that produce millions of eggs, the reproduction of their kind in sharks targeted more on quality than quantity.Characteristic features of cartilaginous fish - internal fertilization and live birth widespread ovoviviparity very significantly reduce the mortality of offspring, enabling a high survival rate and lower fertility.
Depending on the species, sharks can be egglayers, viviparous and ovoviviparous.Egg-laying is almost a third of all species.After internal fertilization, the female lays eggs covered with a protein jelly layer on top of it protected by a hard shell which protects the contents against dehydration and external damage.The stock of nutrients in the egg is enormous, it does not dry out during the complete development of the embryo, which, it should be noted quite long.As a rule, at the same time a small number of eggs deposited from 1 to 12. The only exception is the polar shark lays up to 500 eggs a length of 8 cm. The slow development of the embryo pays off - hatched small shark perfectly adapted to life and is different from the adult sizes only.
ovoviviparity distinctive feature is that hatched from fertilized eggs remain in the oviduct young mother for some time, being born and developed perfectly adapted to independent existence.Information on terms of carrying offspring have ovoviviparous species need to be clarified.According to some, this period ranges from several months to two years, like barbed shark, which is a record among the vertebrates.
in the womb at the same time live-bearing fish can grow up to 30-80 embryos.Regardless of the type and method of shark reproduction, the reproduction of all the distinguished small but capable of independent living offspring.
Plankton Shark
The majority of these fish are distributed in the oceans and seas, living in the water column from the surface to a depth of two kilometers and are classified as real predators.But in this family, there are exceptions: megamouth, basking, whale and several other species of sharks are filter feeders, eating plankton, small fish and squid.
considered largest whale and basking sharks, reaching a length of 20 and 15 meters.As the plankton the fish, they move slowly, opened his mouth, in the center of clusters of plankton, banishing water through the gill openings with special outgrowths-plates, filtering out a huge amount of water and extracting from it all living organisms larger than 2 mm.
It's about playing planktonic species very little information.So, it is the unknown life is a giant shark.Whale - egg-laying.It postpones the eggs reach a very impressive size: the length can be 0.7 m, width - 0.4 m. Despite the huge size, plankton fish shark photos are presented in this article, it is not aggressive and very slow.
world Sharks amazing and diverse.Some of them are bottom living and feed on crustaceans and invertebrates, such as a small cat, the size of not more than 1 meter in length.The fishery is the spiny dogfish, spiny dogfish, a photo of which is also presented in the article.
Fishing katran
Katran having widespread, it is the only species that lives in the Black Sea.It is extremely cold-sea shark, and does not favor the warm waters.Maybe this explains the fact that the Black Sea katran rarely reaches 1 meter in length, although in the North Sea, the size of this fish is 1.5-2 m. The spiny dogfish hardly rise to the surface and are not suitable to the shore.They live at a sufficient depth, stumbling into large shoals.Katrana feed on benthic invertebrates and bottom fish - flounder, whiting, successfully prey on shoals of anchovy.
striking that katran - ovoviviparous fish, whose pregnancy lasts an incredibly long time - up to 2 years.Akulyata born completely ready for adult life predator.Inaccessible to a person protected and carefully, they grow to adulthood without too many problems.These sharks in the sea are safe for humans.They never swim close to the swimmers.The incredible system and a highly developed sense of smell the slightest frequency oscillations katranov helps avoid meeting people.Flocks of fish close to the coast in the late autumn.Then the fishing season begins.The second title of sharks - spiny - given katranov not in vain.This fish is able to deliver a lot of trouble when it is taken out of the trawl.She not only has a solid scales and sharp prickles before dorsal fins, which are located at the base of the poisonous glands.In contact with them you can receive a portion of the poison, though not fatal, but it brings some inconvenience.The most generous catches katrana Atlantic ocean is sometimes possible to catch up to 20,000 fish in one noticed.
Prickly shark - not just a tasty fish, she is very affectionate and will definitely be helpful.In the capable hands of a good cook meat katrana it turns into a magnificent delicacies, healthy and tasty dishes.Immutable rule in the preparation of shark meat is a must drain the blood immediately after the fish caught.In its large concentration of ammonia.If you do not get rid of the blood product will be ruined.The advantage of these dishes is the fact that there is no meat in their bones, because this fish - cartilage.
valued and skin katranov.Abrasive katranov skins have always been used by masters of many industries: from carpenters, cabinetmakers and carpenters to furriers.
tiger shark
fully justify the reputation of a thunderstorm tropical seas, tiger shark, yielding white in the amount recorded attacks on humans, is much greater than its percentage of deaths in the after meetings with her.Title shark define its external features.Tiger shark (tiger or sea), so named because of the dark horizontal stripes on a gray, brown or greenish-gray background of the body, which will eventually fade away.Prefer shallow waters, these sharks rarely drops below 300 meters, the cold water did not attract them.Outstanding fish size - 7-8 meters in length and weighs about a ton - and put it in a number of the larger species.The streamlined shape of the body with a large head, blunt snout and 5th gill slits and a large fall from the jaws 280-300 equipped with flat skrebkoobraznymi serrated teeth, and a well-developed upper lobe of the caudal fin - this is an incomplete portrait of the dangerous fish.
Sea Tigers tied to chose the place, they do not like to travel outside their own accommodation.Being a lone predator, tiger sharks sometimes go astray in the group, if enough food.But more often they patrol their neighborhood alone.
diet of these predators make pinnipeds mammals, dolphins, fish, waterfowl and even smaller members of their own species.They are omnivorous so that the contents of their stomachs, introducing a set of objects that are far from organic food, surprised the researchers.During his exorbitant omnivorous tiger sharks being labeled "sea scavengers".But more than relevant for them is the ability to twist the stomach through the mouth rinse in water which allows to get rid completely indigestible objects such as cans, bags, various types of garbage.
This dangerous shark belongs to the ovoviviparous, nurtured their offspring 14-16 months and give birth in the litter up to 80 sharks, up to half a meter each.
Great White Shark
exceptionally large aggressive predators - the white shark or karharodon, long and firmly holding the sad primacy in the number of attacks on people, found in the surface waters of all the oceans of the Earth, except the Arctic, preferring temperate and warm climate.In cold waters, it is not found, and does not live in brackish or salted waters.For example, in the Black Sea does not appear karharodon.The most likely meet with great white sharks on the coast of California near the Mexican island of Guadeloupe, in the Mediterranean and the Adriatic Sea, off the coast of New Zealand, where they can swim in small flocks.Seas, which are found in abundance sea lions and seals, especially loved by these predators.For a long time believed to be a constant coastal existence of white sharks, however, it proved that the fish migrate from the coast of California to the African latitudes, sailing for the year more than 20 thousand km.
Being the biggest modern predator (individual instances reach a length of 10 meters with a body weight of up to 3.5 tonnes), white shark does not sacrifice any chance of escape.His name is obliged to this kind of color ventral - light or off-white.The dorsal part of the darker colors: gray, greenish.Like all species of sharks, the white is no air bubble, which explains the constant movement of the fish.
food it is more biased than its sister tiger.Small shark feeds on medium-sized fish, mammals.Grown karharodony hunt seals, dolphins, big fish and smaller members of the species.Adults do not pass by the young or sick whales, often performing the attack outstanding tactical moves, that only confirms the presence of their intellectual abilities.This dangerous shark long ago proved that it too tough for any production.
