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23 February 2017

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SAND TIGER SHARKS:
The Amazing Shark

shark

The shark has developed over hundreds of millions of years into one of the worlds most perfect predators. It is a highly developed eating machine.

Sight
Sharks are slightly farsighted and see in color. Their eyes can function in light ten times dimmer than that of the human eye because of a shiny reflective pigment called tapetum lucidum that is also found in cats’ eyes. Some sharks posses a nictitating membrane which closes to protect the eye as the shark attacks prey. In sharks such as the great white the eye rolls upward for protection just before the shark bites.
Hearing
Sharks are attracted to low frequency, pulsing sounds such as the sounds made by injured or dying fish.
Lateral Lines
Series of fluid-filled canals containing hair-like receptors (similar to the cochlea of the human ear) which extend along the sides of the head and body. These sense vibration, change in pressure, movement and sound.
Olfaction
The sharks’ nostril can sense blood in the water as little as one part per million from a mile away. Lemon sharks can sense fish oil in water one part per 25 million or the equivalent of just ten drops in an average home swimming pool, Caribbean reef sharks can sense grouper flesh concentrations as low as one part per 10 billion or the equivalent of one drop in a quarter acre pond.
Ampullae of Lorenzini
Receptor cells located at base of canals on sharks’ snout, lower jaw and around the eyes. The Ampullae of Lorenzini detect electrical fields, their direction, and strength. Every living creature gives off an electrical field which provides a stimulus or homing device for the shark. Some sharks can detect a change in direction of electrical intensity five-billionths of a volt per centimeter in a range of 0-8 Hertz. This sense can also be used to detect changes in the sharks’ own bioelectrical field. It is believed that sharks use this sense to detect changes in the earths’ magnetic field and for navigation.
Range of sensory organs:
Sound - distances of a couple of miles
Smell - distances of several football fields
Lateral line - distances of several football fields
Vision - distances of dozens of feet
Ampullae of Lorenzini - distances of several feet
Touch & Taste - contact

It is thought that the shark uses the strongest sensory stimulus first and then shifts to whichever sense is stimulated most as it meets its prey.

Text © Beth Bader 1996 (with additions by Rick Allen).