Since sharks can track electrical changes so well, scientists also are investigating whether electroreception plays a role in their navigation skills. The higher salt concentration increases the intensity of the electrical field around the victim. Instead of going for the fresh meat of the rescuer, sharks will be repeatedly drawn to their previous victims because of the salt released from blood in the water. The power of electroreception also explains why sharks will continue attacking human victims even while being rescued by another person. Through this type of research, scientists are hoping to develop a shark deterrent that tricks its electroreception sense. For example, when given the option between dead fish and an electrically charged rod, a shark will initially head for the fish, then alter its course toward the metal rod at the last minute. In experiments testing sharks' electroreception skills, scientists have confirmed that the fish will indeed make last-minute feeding decisions based on electrical impulses. For that last few feet of the attack, great white sharks actually roll their eyes back into their heads for protection and let electroreception take over navigation. It's only when the shark gets about 3 feet (1 meter) away from its target that electroreception kicks in to orient its jaws for an accurate, final attack. Since two-thirds of a shark's brain is devoted to smell, its olfactory sense can get the shark hot on the trail of its next meal even in dark waters. The lateral line and electroreception, along with sharks' other senses combine to make them incredibly keen hunters. This system allows sharks to sense water displacement, pressure and direction. The long, hollow tube opens out into the skin at perforated scales. The lateral line is a sensory organ in many fish and amphibians that stretches down their sides from gills to tail. The ampullae de Lorenzini compose part of sharks' lateral line. How can sharks do that? Read about the part of sharks' bodies that regulate this unique internal homing device on the next page. If two AA batteries were connected 1,000 miles (1,600 kilometers) apart, a shark could detect if one ran out. Sharks can sense the tiniest changes in this electrical current, down to one-billionth of a volt. Because fish cells have a charge different from the saltwater solution in which they swim, the contact creates a weak voltage in the same way as a battery. When connected by a wire, those opposite charges attract, meaning the positive and negative particles flow toward each other to pick up or drop off electrons to become stable again.Ī similar thing happens in the interaction of living cells and salt water. It's set up like an electrochemical cell that separates the negatively and positively charged ions. You can compare this to how batteries work. In water, these sodium and chlorine ions in salt separate and move freely, transporting electricity. Ions are particles that have an electrical charge because they have lost or gained an electron. Salt in salt water contains sodium and chlorine ions. Open air does not conduct this electricity away from our bodies, but thankfully for sharks, salt water does. At hospitals, electrocardiogram machines track the electricity resulting from our heart beating. What does electricity have to do with sharks' underwater habitat? Any muscular movement or twitches in living animals and fish create small electrical currents. Electroreception simply means the ability to detect electrical currents.
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