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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.
It is recognizable because of its seven gill slits, while most shark species have five gill slits, with the exception of the members of the order Hexanchiformes and the sixgill sawshark. This shark has a large, thick body, with a broad head and blunt snout. The top jaw has jagged, cusped teeth and the bottom jaw has comb-shaped teeth.
Blacknose sharks are preyed upon by larger sharks, [7] and captives have been observed to perform an apparent threat display towards encroaching divers or newly introduced members of their species. The display consists of the shark hunching its back, lowering its pectoral fins, gaping its jaws, and swimming with an exaggerated side-to-side motion.
In the winter, the sharks scavenge on market squid (Loligo opalescens), which die by the tens of thousands after their mass spawning event. [3] [6] Horn sharks hunt mainly using their sense of smell. [4] Although electroreception certainly plays a role in locating prey, this species has only 148 ampullae of Lorenzini.
In the northwestern Atlantic, the bignose shark conducts a poorly documented seasonal migration, spending summer off the US East Coast and winter in the Gulf of Mexico and the Caribbean Sea. Individual sharks have been recorded traveling distances between 1,600 and 3,200 km (1,000 and 2,000 mi). [1] [4]
With his hand close to razor sharp teeth, shark expert Neil Harvey attempts tonic immobility in a large reef shark. Tonic can be induced by turning a shark upside down, but that's not the only way.
An angler in Nags Head caught a great white shark off a pier in October.
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.