megamouth-100

鲨鱼的资料（英文）

鲨鱼属于脊椎动物门软骨纲(Chondrichthyes)板鳃亚纲，海生，少数种类进入淡水，为一群游速快的中大型海洋鱼类。

Sharks are vertebrates steel door cartilage (Chondrichthyes) elasmobranchii, Marine, a few species enter fresh water, as a group of large Marine fish speed is fast.。

鲨内骨骼完全由软骨组成，常钙化，但无任何真骨头组织，外骨骼不很发达或退化，身体常被皮齿(质鳞)，牙多样化，具有硬肌，但膜骨则永不存在，脑颅无缝。

Shark endoskeleton completely composed of cartilage, often calcified, but without any true bone tissue, degraded or exoskeletons is not very rich, the body is often skin teeth (scale), tooth diversification, with hard muscle, but never exist, membrane bone temple seamless.。

上额由腭方软骨组成，下额由梅氏软骨组成。最新研究表明，鲨体内含有多种生物活性成分，如抗癌因子、角鲨烯、黏多糖等等。

On the forehead is composed of palatal side cartilage, the forehead is composed of Mr Medvedev cartilage.Sharks, according to new research in the body contains a variety of biological active ingredients, such as anti-cancer agent, squalene, mucopolysaccharides and so on.。

扩展资料

鲨鱼的起源不详，但其地质学纪录可追溯到泥盆纪(4.08亿～3.6亿年前）。鲨鱼化石在中泥盆世出现，在石炭纪（3.6亿～2.86亿年前）成为占优势的脊椎动物。现代鲨鱼出现于侏罗纪早期（2.08亿～1.87亿年前），到白垩纪（1.44亿～6,640万年前）已经发展成现存的各科。

总之，除觅食和游泳机制的改进外，进化对鲨鱼的形态改变甚微。无论对化石种和现存种类来说，牙齿在鲨鱼种类鉴别方面均有很重要作用。

参考资料来源：百度百科-鲨鱼

How long have sharks existed? 。

Fossil records indicate that ancestors of modern sharks swam the seas over 400 million years ago, making them older than dinosaurs! They are considered to be the first vertebrate with a complete jaw. Throughout time sharks have changed very little. 。

What is an "elasmobranch"? Elasmobranchs are a closely related group of fishes, differing from bony fishes by having cartilaginous skeletons and five or more gill slits on each side of the head. In contrast, bony fishes have bony skeletons and a single gill cover. Elasmobranchs include sharks, rays, and skates. 。

Do sharks have bones? 。

No, sharks and all other fishes belonging to the class Chondrichthyes lack true bone, but rather have cartilaginous skeletons. 。

How long do sharks live? 。

While longevity data are not available for many sharks, maximum ages do vary by species. Some sharks like the smooth dogfish (Mustelus canis) may only live 16 years, while others such as the porbeagle shark, (Lamna nasus) may live as long as 46 years. Whale sharks (Rhincodon typus) the largest fish in the world may live over 100 years. 。

What does a shark's skin feel like? 。

Shark skin feels exactly like sandpaper because it is made up of tiny teeth-like structures called placoid scales, also known as dermal denticles. These scales point towards the tail and helps to reduce friction from surrounding water when the shark swims. Because of this, if someone rubbed the skin from the head towards the tail, it would feel very smooth. In the opposite direction it feels very rough like sandpaper. As the shark grows, the placoid scales do not increase in size, but rather the shark grows more scales. The silky shark (Carcharhinus falciformis) has small scales giving it a "silky" feel to the touch. 。

Do sharks sleep? 。

It was once believed that all sharks had to swim constantly in order to breathe and could not sleep for more than a few minutes at a time. Oxygen-rich water flows through the gills during movement allowing the shark to breathe. While some species of sharks do need to swim constantly, this is not true for all sharks. Some sharks such as the nurse shark have spiracles that force water across their gills allowing for stationary rest. Sharks do not sleep like humans do, but instead have active and restful periods.。

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