Physics in the animal world: electric eel and its "power station"
Electric eel (Source: youtube) The
fish of the species electric eel (Electrophorus electricus) is the only representative of the genus of electric eels (Electrophorus). It occurs in a number of tributaries of the middle and lower reaches of the Amazon. The body size of the fish reaches 2.5 meters in length, and weight - 20 kg. It feeds on electric eel fish, amphibians, if lucky - by birds or small mammals. Scientists have been studying electrical eel for dozens (if not hundreds) of years, but only now some of the structural features of its body and a number of organs have begun to clear up.
And the ability to produce electricity is not the only unusual feature of electric eel. For example, it breathes atmospheric air. This is possible due to the large number of special types of tissue of the oral cavity, penetrated by blood vessels. For breathing, eel needs to float to the surface every 15 minutes. He cannot take oxygen from water, because he lives in very muddy and shallow reservoirs, where there is very little oxygen. But, of course, the main distinguishing feature of electric eel is its electrical organs.
They play the role of not only weapons to stun or kill its victims, which the eel eats. The discharge generated by the electric organs of the fish may be weak, up to 10 V. The eel generates such discharges for electrolocation. The fact is that the fish have special "electroreceptors" that allow you to determine the distortion of the electric field caused by its own body. Electrolocation helps eel find its way in muddy water and find hidden victims. Eel can give a strong discharge of electricity, and at this time hidden fish or amphibians begin to twitch randomly due to convulsions. The predator easily detects and eats these preys. Thus, this fish is both electroreceptual and electrogenic.
Interestingly, the acne generates discharges of various strengths using three types of electric organs. They occupy about 4/5 of the length of the fish. Hunter and Maine organs generate high voltage, and Sachs organ generates small currents for navigation and communication purposes. The main organ and the organ of Hunter are located in the lower part of the body of the eel, the organ of Sachs is in the tail. Acne "communicate" with each other using electric signals at a distance of up to seven meters. With a specific series of electrical discharges, they can attract other individuals of their own species.
How does electric eel generate electrical discharge?
Eels of this species, like a number of other "electrified" fish, reproduce electricity in the same way as the nerves with muscles in other animals, for this purpose they use electrocytes - specialized cells. The task is performed using the enzyme Na-K-ATPase (by the way, this enzyme is also very important for the mollusks of the genus nautilus (lat. Nautilus)). Due to the enzyme, an ion pump is formed, pumping sodium ions from the cell and pumping potassium ions. Potassium is derived from the cells due to special proteins that make up the membrane. They form a kind of "potassium channel" through which potassium ions are removed. Inside the cell accumulate positively charged ions, outside - negatively charged. An electric gradient arises .
The potential difference as a result reaches 70 mV. In the membrane of the same cell of the electric organ of eel, there are also sodium channels through which sodium ions can again enter the cell. Under normal conditions, for 1 second, the pump removes about 200 sodium ions from the cell and simultaneously transports approximately 130 potassium ions into the cell. On a square micrometer membrane can accommodate 100-200 such pumps. Usually these channels are closed, but if necessary, they open. If this happens, the chemical potential gradient causes the sodium ions to enter the cells again. There is a general change in voltage from -70 to +60 mV, and the cell gives a discharge of 130 mV. The duration of the process is only 1 ms. Electric cells are interconnected by nerve fibers, the connection is sequential. Electrocytes are peculiar columns, which are already connected in parallel. Total voltage of the generated electrical signalreaches 650 V, current - 1A. According to some data, the voltage can even reach 1000 V, and the current strength is 2A.
Electrocytes (electrical cells) of eel under a microscope.
After the discharge, an ion pump acts again, and the electric organs of the eel are charged. According to some scientists, there are 7 types of ion channels in the cell membrane of electrocytes. The location of these channels and the alternation of types of channels affects the speed of electricity production.
Electric battery discharge
According to a study by Kenneth Catania (Kenneth Catania) from Vanderbilt University (USA), an eel can use three types of discharge of its electrical organ. The first, as mentioned above, is a series of low-voltage pulses that serve for communication and navigation purposes.
The second is a sequence of 2-3 high-voltage pulses lasting several milliseconds. This method is used by eel when hunting for a hidden and hidden sacrifice. As soon as 2-3 high voltage discharges are given, the muscles of the lurking victim begin to contract, and the eel can easily detect potential food.
The third method is a series of high-voltage high-frequency discharges. The third method uses eel during hunting, giving up to 400 pulses per second. This method paralyzes almost any animal of small and medium size (even humans) at a distance of up to 3 meters.
Who else is capable of producing electric current?
About 250 species of fish are capable of this. For most, electricity is only a means of navigation, as, for example, in the case of the Nile elephant (Gnathonemus petersii).
But the electric discharge of sensitive force is capable of generating few fish. These are electric stingrays (a number of species), electric catfish and some others.
Electric catfish (Source: Wikipedia)
Jason Gallent and colleagues conductedsequencing of the genome of a number of fish with electric organs, and found that many of the species they studied are not related. The "invention" of the nature of the electric organs of the fish went in parallel, but the structure of the batteries is very similar for all. In total, scientists counted 6 independent evolutionary lines that led to the emergence of electrical organs. Perhaps the electric eel is one of the types of fish that use this body most skillfully.