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The thresher sharks have an extreme example of this tail in which the upper lobe has evolved into a weapon for stunning prey. Bottom-dwelling sharks such as catsharks and carpet sharks have tails with long upper lobes and virtually no lower lobe. The upper lobe is held at a very low angle, which sacrifices speed for maneuverability.
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.
The order Hexanchiformes is a very small and primitive order consisting of cow sharks and frilled sharks. These sharks have only 1 dorsal fin, 6-7 gill slits, and no nictitating membrane on the eyes. Cow sharks are fairly large and stocky, while frilled sharks are smaller and have eel-like bodies.
Although salmon sharks are thought to be capable of injuring humans, few, if any, attacks on humans have been reported, but reports of divers encountering salmon sharks and salmon sharks bumping fishing vessels have been given. [17] These reports, however, may need positive identification of the shark species involved.
Such gills are characteristic of cartilaginous fish such as sharks and rays, as well as deep-branching vertebrates such as lampreys. In contrast, bony fishes have a single outer bony gill covering called an operculum. Most sharks and rays have five pairs of gill slits, but a few species have 6 or 7 pairs. Shark gill slits lie in a row behind ...
Humans have a variety of personality traits. And now, a new study says sharks have personalities as well. Yes, sharks. Researchers at the Marine Biological Association of the UK and the University ...
Distinctively, these fish have no jaws. [15] Cartilaginous fish such as sharks also have simple, and presumably primitive, skull structures. The cranium is a single structure forming a case around the brain, enclosing the lower surface and the sides, but always at least partially open at the top as a large fontanelle.
Greenland sharks have also been found with remains of moose, polar bear, horse, and reindeer (in one case an entire reindeer body) in their stomachs. [11] [24] [20] The Greenland shark is known to be a scavenger and is attracted by the smell of rotting meat in the water. The sharks have frequently been observed gathering around fishing boats. [11]