News & Views
What Is Electroreception, and How Do Sharks Use It to Hunt?
Jul 15 2016
While they may step up as one of the world’s most feared predators, most sharks crash and burn in the eye department. Ever noticed how a shark’s eyes are small and beady compared to the proportion of its head? Exactly. Rather than hone in on their prey using their eyes, sharks are armed with a ‘sixth sense’ called electroreception.
This is what allows them to hunt fast and fierce underwater. So how does electroreception work? While they’re more or less invisible to the naked eye, sharks have specially developed pores around their faces which act as honing devices. They actively detect the electrical currents of other organisms, which travel through the water and are processed by the shark’s brain in the form of neurotransmitters. It’s a sophisticated process, and has serious evolutionary street cred.
In simple terms, electroreception can be compared to batteries. In the same way that batteries emit positive and negative charges, so too does salt water thanks to the presence of sodium and chlorine ions. The bodies of fish and other organisms also create a faint electrical charge as their muscles contract. When energised cells from fish come into contact with free-floating sodium and chlorine ions an electron exchange takes place in a bid to stabilise the collision. This triggers a weak voltage that sharks are able to sense using electroreception.
A salt water phenomenon
Wondering why animals on dry land don’t hunt down prey using electroreception? Ultimately, it’s all about the presence of salty H20. Sodium and chlorine ions are a must for creating the faint electrical charge that occurs during the electron exchange. Thus while humans and other land animals do spur electrical impulses when muscles contract, the lack of H20 means they don’t radiate away from the body.
Ampullae of Lorenzini
Sound quirky? The term is a mouthful, and is the scientific name for the special sensing organs that facilitate electroreception. The tiny jelly-filled pores actively respond to electrical currents, and in turn trigger the release of neurotransmitters in the shark's brain. Thanks to around 1,500 of these pores, sharks then know that a potential meal is lurking nearby.
Sharks may be near blind, but they have insanely refined electroreception skills. Scientific American reports that some species can detect electric currents as weak as one-billionth of a volt, while Discovery News claims that if two AA batteries were connected 1000 miles away, a shark would definitely know about it.
While sharks may be formidable hunters, they still face risks of their own. ‘Accurate Analysis of Low Levels of Mercury in Fish Using Vapour Generation AA’ looks at the issue of industrial mercury emissions, and its eventual deposition in rivers and oceans.
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