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Fish with 'stunning power'

What do you know about animals that produce electricity? They certainly are an amazing segment of the animal kingdom, which is packed with creatures of varied species, with extraordinary abilities that man does not have. Let's check out which animals generate electricity, and for what purpose they do so...

It is in the underwater world that we come across creatures generating electricity. Some fish generate enough electricity to pack a punch that is literally 'shocking', while others produce enough electricity for less violent purposes.

The different types of fish generate electricity using their organs modified from different muscles, but they all use the same method to do so.

What exactly is a fish's electric organs composed of is worth examining. Of course, they are not like the electric organs that you may be familiar with, in the field of music.

These 'electric organs' have flattened cells stacked in vertical columns like coins, which are known as electro plaques. Each of these electroplaques normally produces a little more than 0.1 volt, but since the individual cells are connected in each column, which are in turn linked in parallel, the overall electric charge becomes very powerful. For instance, a large electric ray has the ability to stun or kill a prey with a high-voltage blast of about 200 volts.

Water, we know is a good conductor of electricity, but seawater conducts it more efficiently than freshwater. This means that saltwater species of electric fish do not have to generate such high voltages as their freshwater counterparts, to produce the same current.

In order to overcome the inherent resistance freshwater has to electricity, when compared to saltwater, the freshwater species are equipped with taller columns of electroplaques than marine species. But of course these columns are less in numbers.

Of the marine species powered with electricity, the most potent (powerful) is the electric ray which is also known as the torpedo.

Electric rays are mostly found in the Mediterranean and the subtropical Atlantic. Its ability to produce electricity was known since ancient Greek and Roman times. It is even said that ancient Roman physicians used this electric charge, which stems from a pair of large electric organs located in its huge round pectoral fin, just behind each eye, to cure patients suffering from headaches or gout.

How? They did so by strapping a living torpedo or electric ray to the patient's head! Now doesn't that send a shiver down your spine......just imagine using that method of electric shock today?

There are many other types of fish that generate a lesser voltage. Marine rajid skates are one such species. These skates dwell mostly at the bottom of the sea, and their electric organs are located in their tails.

A relative of the perch, the electric stargazer is another fish that uses its electric organs, located in deep pits behind the eyes, to not only stun its prey, but also as a defence against predators. It usually lies in wait for its prey, buried in the sand, with only its eyes protruding, and once the victims come close enough, it seizes them, by stunning them.

Among the freshwater fish that have the ability to generate electricity, the most powerful is the Amazon electric eel. Measuring up to about 3m (10 ft), it can produce a 550-volt blast, out of its tail. It has three electric organs, two of which are used for navigation and prey detection.

The third, and the largest is the formidable weapon. Split into two long, lateral halves, it discharges 550 volts into the freshwater out of its tail, killing fishes and even frogs. Its electrical discharge is powerful enough to kill even humans and horses, if they are present in the water, at the time of discharge.

Another sea creature that uses its electric power to stun prey, is Africa's freshwater cat fish which can discharge around 350 volts from an electric organ surrounding its body. Like the eel, it also uses this powerful organ to detect would be attackers. It is also recorded that in captivity, this cat fish which is sensitive to the Earth's magnetic field, responds to magnetic currents generated several hours before an impending earthquake.

Mormyrids and knifefish gymnotids use their electrical organs to navigate. Mormyrids, also known as elephant trunk fish, have three electro sensory channels, each carrying specific types of information from electro receptors in the skin to the central brain area, for analysing and intergration. The mormyrid's detection mechanism is so sensitive that it is able to not only distinguish between different species of fish, but also between different sexes of its own kind.

The navigation system of mormyrids and the knifefish gymnotids are similar to the echolocation used by bats. Some mormyrids derive their electric organs from the muscles at the base of the tail, but gymnotids derive it mostly from their flank muscles.

There are many new species of electric fish that have been discovered, especially in the dark, deep waters of the Amazon river. It is said that two such species prey on other electricity-generating species, and bite off and devour their tails.

They have a steady supply of their peculiar food because their victim's tail regenerates fast. New varieties of animals are being discovered all the time. Keep checking for such new discoveries, you are bound to be amazed at some of the bizarre creatures that inhabit our planet.

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Copyright 2001 The Associated Newspapers of Ceylon Ltd.