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Electrosensitive creatures on land and water

We enlightened you about the 'electric powers' some creatures living in water have, and how they put it to good use; to stun and kill their prey and to navigate. But, electric powers aren't just restricted to torpedo rays, eels, mormyrids and knifefish. Other members of the animal kingdom too get a charge out of life with the electric powers they are bestowed with. These include sharks, snakes and platypuses.

Even though sharks do not have organs that generate electricity, like the electric rays and other creatures, we featured last week, they have electrosensitive organs, that help them detect electrical fields as minute as 0.005 millivolt, produced by the muscles of any prey nearby. These numerous electrosensitive organs which are known as ampullae of Lorenzini are tiny jelly-filled structures located beneath the skin. They are open through external pores onto the surface of the shark's snout.

These are so sensitive that the shark can even find flatfish that are hiding in the sand, with their help. The great white shark (Carcharodon carcharias) homes in on its victims with the help of these electrosensitive organs. During the brief period of blindness the great white shark experiences, when it rolls back its eyes out of harm's way, as it opens its jaws to bite a victim, the shark is guided by the electrical information provided by these tiny organs. These ampullae of Lorenzini enables the great whites to home in to even very weak electrical fields, in order to ensure accuracy of its bite.

In the hammerhead shark, these electrosensitive organs are profusely(abundantly) scattered across its broad head. As a result of this, the hammerhead shark is able to scan a wide area for electrical traces coming out of stingrays, its favourite prey, hiding in the sandy sea bed.

Another creature researchers discovered as recently as the mid 1980s that possesses electro receptors, is the platypus.

When a platypus dives underwater, it always closes its eyes, ears and nostrils.

So, how it succeeded in detecting, shrimps, fish and frogs was a baffling question. It was assumed by most researchers that this was done by simply sensing its prey.

However, studies have proved otherwise and today it has been established that platypuses have tiny electroreceptors all over their bills. But even though in electrosensitive fish these receptors are linked to the auditory cranial (skull) nerve, in the platypuses, the corresponding receptors are linked to the trigeminal cranial nerve.

Recent research has revealed that three facets of behaviour and physiology of the rattlesnake - that is silent rattling, tongue scanning and triboelectricity, may be linked to electricity generation.

It has always been believed that the rattlesnake rattled to scare off victims. However researchers have discovered that even juvenile snakes which have not yet developed their rattles sufficiently to make that familiar sound, go through the motions of vibrating their tails, known as silent rattling.

Another odd behaviour of these snakes, is tongue scanning. It occurs when the snake waves its tongue above an object, flicking its forked tongue without directly touching it.

Normally snakes directly touch objects with their tongues when feeding or tracking prey, but before doing so, they practise tongue scanning and this was believed to be done with the objective of collecting olfactory particles from the air. But now researchers think it may have served another purpose.

Triboelectricity is the third mysterious behaviour. This is the process of generating electricity through friction. Like other dry-skinned land animals, rattlesnakes acquire a positive electrostatic charge through friction when sliding across the Earth's surface. However, unlike other creatures that have hairs, bristles or spines that serve as multiple discharge points, rattlesnakes and other serpents do not have such discharge points. Yet, they appear to be able to not only acquire, but also to retain an electrostatic charge.

Studies carried out in the 1990s by researchers, as recorded in the journal Nature states that rattlesnakes generate electrostatic charges when they vibrate their rattles. Experiments had revealed that when stationary, the rattle would not produce a voltage, but when vibrated 60 times per second, a charge of 50-100 volts was yielded.The researchers had proposed that a rattlesnake's electrostatic charge may serve as an aid to navigation. According to their theory, the snakes may be tongue scanning to reach the electrical charges of the landscape as they move about.

Sensitivity to electrostatic charges also may be useful in leading the snake to potential prey. The possibility of rattlesnakes having electroreceptors is intriguing and much research is being done into this area to establish this new theory.

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