Class – Cartilaginous fish / subclass – Plasminogene fish (Elasmobranchii) / Superorder Sharks (Selach)
History of the study
The history of the evolution of hammerhead sharks has been very successful. In our days it is one of the most common shark species in the world, and in some places they’re just going in astounding quantities. Hundreds of individuals run around seamounts.
Few other species of sharks form such large flocks. This is one of the greatest mysteries of the ocean. Why are so many of these sharks gathered in one place, at one time. Oddly enough, in these large schools the majority are female, and we don’t yet know why this happens.
Widely distributed in tropical and temperate waters of all oceans, except, of course, the Arctic. Most commonly found in the Gulf of Mexico and Caribbean sea, near Hawaii, Philippines, New Zealand and many other seas of warm and temperate latitudes.
Hammerhead shark is truly one of the most unusual sharks. Her appearance seems truly alien, but it is quite common in tropical seas around the world.
When you look at the shark hammer head there is just one question – why this animal has this kind of pharmagology? What is it? And how it appeared? After all, nature creates freaks. And if it generates by mistake, they can not compete with “normal” types and die. All the more strange that there are many types of hammerhead sharks of all shapes and sizes, at least 9 different species. Surely nature could make so many mistakes and “give birth” so many freaks, well there are millions of years?!
Features of the structure
The main distinguishing feature of the family of sharks is the shape of their heads – it is a very unusual form – in the form of a hammer, T-shaped. Different types of hammerhead sharks, there are some distinctive features in the shape of the head. The edges of the T-shaped growths on the head of sharks are eyes. At the bottom of the nostrils and the special sensory organs of sense, which are described below. As the eyes of a shark are on the sides of her body, she can’t see in front of him, so when driving, hammerhead sharks make side head movements, which helps them to increase the viewing angle of almost 360 degrees.
Sharks hammers reproduce in an unusual way: unlike most fish they are viviparous. In the mother’s body the fetus develops and is nourished through a system similar to the placenta of mammals, but sharks are born the hammer is rotated back toward the body. This facilitates the birth. With age the head becomes a known T-shaped, which distinguishes adult sharks. But why these sharks are viviparous, when almost all other fish are oviparous?
The lifestyle of the shark, the hammer, apparently, are not very different from other large relatives of the suborder Poperechnaya. The only difference found in the fact that they prefer muddy seabed every other seat, probably because eat mainly stingrays and flounder. However, they are by no means limited to these and other deep sea fish, but also arise in the upper layers of water, watch for raids on the ships and can be dangerous for people. “These are huge, horrible and cruel animals, says Gesner, not swim to shore, whereupon as if by accident caught only the smallest of them; they eat all kinds of fish, swallow and devour floating people.
Food hammerhead sharks are small bony fish, crustaceans, squid, as well as representatives of medium-sized sharks and even stingrays, whose thorns are often found in the stomachs of these sharks. The larger hammerhead shark, especially individuals a giant hammerhead shark can eat larger prey. The teeth of these sharks are smaller than the great white or tiger shark, they are very sharp, almost triangular in shape. The size of the teeth of this shark suggests that it is not the traditional mining of very large size.
The largest representative of the family, a giant hammerhead shark (Sphyrna mokarran) — reaches 4, 5 and even 6 m in length. It is widely distributed in tropical waters of Pacific, Indian and Atlantic oceans, but never reaches high numbers. Other hammerhead sharks have smaller sizes about 3, 5-4, 2 m with a weight of about 450 kg. they also have a predominantly tropical distribution. Only one species — common hammerhead (Sphyrna zygaena) — in the summer time visits moderately warm water. It is marked in Northern and Japanese (Peter the Great Bay, Tatar Strait) seas and the North-East coast of the U.S. and off the coast of England.
Hammerhead sharks and people
Large hammerhead sharks pose a significant risk to people in water. In its stomach they found human body parts, and many of the attacks occurred in front of numerous spectators, are documented. One such attack was committed on a crowded beach off the coast of Florida, just 60 m from the shore. The affected girl were seriously injured but was pulled from the water by the lifeguard on duty. The hammerhead accompanied his prey escaped to shore.
The commercial value of the hammerhead slightly, but in some areas they are hunted for meat, skins and liver oil. The sharks providing stubborn resistance when caught, are also considered very honorable trophy for saltwater anglers.