Characteristics of sharks?

Sharks are long spindles. Lateral branchial fissure, normal pectoral fin, not healing with anterior snout; Dorsal position of the north fin; Crooked tail type.

The body is spindle-shaped with cheeks on both sides of the head, but it is similar to ordinary fish. With a few exceptions, the typical shark skin is hard and dark gray, and the dentate scales make the skin look rough. The tail is strong, asymmetrical and upturned; Fins are pointed; The nose and mouth are pointed and protruding, the mouth is crescent, and there are triangular fangs under the nose and mouth. Sharks don't have swim bladders, so they need to swim constantly to avoid sinking into the water.

80% species of sharks are below 1.6m in length, and most sharks are small fish. Among sharks, the largest whale shark is also called Whale Pattern, with a body length of 20m and a weight of 7,000-8,000 kg, which can be described as the king of fish, and the smallest is the wide-tailed small horn shark (also called small spotted shark), with a mature male fish 15cm and a female fish of 20cm.

A giant man-eating shark, a tertiary stratigraphic fossil, was found, with a tooth length of 15.24cm and an estimated body length of 90 m. The American Museum of Natural History exhibited this bimaxillary model, which can accommodate six people standing in their mouths.

Extended data

Most sharks can be eaten fresh, steamed and pickled, or used as raw materials for fish sausages, fish sauce and canned fish. When eating fresh, because the meat contains urea, citric acid, lemon juice or tomato juice can be used to remove urea to improve the meat quality. In addition, shark's fin (shark's fin) and fish lips are two of the eight treasures of seafood.

Because sharks are high-end consumers in the marine food chain, heavy metal pollutants, especially mercury, are seriously deposited in sharks, so it is not recommended to eat shark fins.

Some large aquariums at home and abroad have set up shark halls to raise more than 0/kloc-0 kinds of sharks with warm training and ornamental value, such as striped spotted bamboo shark (also known as spotted bamboo dog ground) and leopard shark (also known as big-tailed tiger pattern). The breeder sneaked into diving pool (box) to feed or dance with sharks, and showed the mysterious shark world to tourists.

Almost all sharks are carnivorous species, and only a few species, such as whale sharks and basking sharks, feed on plankton. Carnivorous sharks have developed two collars. The lower collar has strong contractile muscles and sharp teeth, so it has a strong bite force. They can eat mollusks, crustaceans, large fish and marine mammals, and even attack ships and bite people. In marine ecosystem, shark is the top of biological chain and plays an important role in maintaining ecological balance.

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