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"Typical sharks", such as requiem sharks, have tails with the upper lobe longer than the lower. The upper lobe is turned upwards at a moderate angle relative to the body, which balances cruising efficiency with turning ability. The thresher sharks have an extreme example of this tail in which the upper lobe has evolved into a weapon for ...
This gives these areas much of the same strength found in the bony tissue found in other animals. Generally sharks have only one layer of tesserae, but the jaws of large specimens, such as the bull shark, tiger shark, and the great white shark, have two to three layers or more, depending on
Many sharks can contract and dilate their pupils, like humans, something no teleost fish can do. Sharks have eyelids, but they do not blink because the surrounding water cleans their eyes. To protect their eyes some species have nictitating membranes. This membrane covers the eyes while hunting and when the shark is being attacked.
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Sharks and rays typically have five pairs of gill slits that open directly to the outside of the body, though some more primitive sharks have six or seven pairs. Adjacent slits are separated by a cartilaginous gill arch from which projects a long sheet-like septum , partly supported by a further piece of cartilage called the gill ray .
It is likely that most captured sharks survive to be returned to the water alive, as this species can tolerate being out of water for an extended period of time. From 1988 to 1991, there was a New Zealand shark liver fishery and reported catches of draughtsboard sharks were 74–540 tons per year. After the fishery was discontinued, catches ...
By rubbing its nose, Neil overstimulates. With his hand close to razor sharp teeth, shark expert Neil Harvey attempts tonic immobility in a large reef shark.
Why do sharks attack humans? According to the Shark Research Institute, there are over 400 plus species of shark around the world, which include great white sharks, tiger sharks and bull sharks.