Sharks (lat. Selachimorpha) is a superorder of cartilaginous fish comprising eight teams, twenty families and about 350 species. Members of the superorder widely distributed in all seas and oceans, there are also freshwater sharks. Most species belong to the so-called real predators, some species, particularly whale, and giant deep-sea sharks, eat plankton.
For many millions of years before the planet appeared the first man, ruler of the prehistoric seas was a shark. The power of evolution sowed on Earth, countless forms of life that could not stand the severe tests and disappeared one after another, as the shark continued to exist. One prehistoric era is succeeded by another, have any amphibians, reptiles, birds, and mammals – the shark continued to exist. Pterodactyls – the winged reptile for millions of years plied the skies, disappeared from the face of the Earth. Dinosaurs-Triceratops, Brontosaurus, allosaurus and many other “saurus”, it is important chestvovali on our planet died out, leaving no trace. As the shark continued to exist.
About 20 million years ago in the sea scoured a huge Stingray, weighing over 100 pounds, and more than 25 different species of sharks, including sharks, reaching 36 meters in length. The length of these monstrous sharks was Opredelenie their huge teeth. Some of the teeth found in California, weighing 340 grams each and reach 15 centimeters in length, and seven – and ten teeth are quite common. They are triangular in shape and closer to the teeth of modern great white sharks that do not exceed 5-6 inches now with a body length of shark of 12 meters (maximum length). These teeth belonged to the ancestor of the modern great white shark the carcharodon, in huge quantities inhabited the seas. When they were first found in the seventeenth-century scientists, naturalists believed that this fossil bird tongues or teeth of serpents. They could not imagine that this shark’s teeth, and ascribed them to the mythical animal. Continue reading
White sea belongs to the basin of the Arctic ocean and represents a huge reservoir polutoratonny. Seas of this type are relatively few. Similar characteristics possess Black sea, the Mediterranean, the Baltic and Hudson Bay. White sea is the smallest of them. It is divided into two unequal parts – the Northern (outer) and southern (inner). They are joined by a relatively narrow Strait, also called the throat.
In modern times, few bodies of water that don’t pollute and the White sea is no exception. Anthropogenic pollution of the White sea began immediately after the occurrence on its shores of a man and eventually became so significant that the consequences can be observed today.
In a relatively short era of navigation, some areas of the bottom, especially in small lips, where it is convenient to stand during the storm, were so covered with coal slag, which still have not recovered destroyed the bottom biocenoses. These environmental problems of the White sea cannot be considered modern, though harm from them not less.
The woodworking industry has no less impact on the ecology of the White sea. Wastes at sawmill one keretsky industrialist, was filled in the Strait between the two Islands on which it is located.The forest industry is one of the key environmental problems of the White sea. Continue reading
Atkritumu fish. One dorsal fin. Pelvic fins located on the belly. In the pectoral fins and in most species the dorsal fin is spiny, often jagged rays. Non-rising mouth surrounded by tendrils. The jaws teeth. Body naked or covered with bony plates. Many have an adipose fin.
The inhabitants of the mainly tropical and subtropical freshwaters of South and Central America, Africa and Asia.
The squad consists of 20-30 families and over 1,200 species. 2 family of marine fish.
The Catfish Family – Siluridae
Body naked, elongated. Adipose fin not. The head is flattened, the mouth large, polverini. Dorsal fin short (not more than 5 rays). Anal fin long, not less than 70 rays. These freshwater and brackish-water predatory fish with spring and summer spawning. They live in fresh water in Europe and Asia, in addition to the basin of the Arctic ocean.
The family includes 8 genera, 2 of which are found in our country.
Rod Catfish – Silurus. Antennae 3 pairs. Thorn in the pectoral fin is smooth.
The genus includes 2 species.
Com S. glanis Linne, 1758. Front mandibular barbels shorter than the back. Spiny rays of the pectoral fin is strong (Fig. 110, 1). Reaches a length of 5 m. of residential Forms and the checkpoint form. These fish developed to take care of offspring. Soma build primitive nests from vegetation remnants.Inhabit the waterways of Europe: the Rhine, North to South Finland, and South to Asia Minor. Continue reading