Electric fish. How do eels and stingrays produce electricity? Does an eel give an electric shock?
Occur, for example, in many plants. But the most amazing carrier of this ability are electric fish. Their gift of producing powerful discharges is not available to any other animal species.
Why do fish need electricity?
The ancient inhabitants of the sea coasts knew that some fish can strongly “beat” the person or animal that touched them. The Romans believed that at this moment the inhabitants of the depths released some kind of strong poison, as a result of which the victim experienced temporary paralysis. And only with the development of science and technology it became clear that fish tend to create electrical discharges of varying strengths.
Which fish is electric? Scientists claim that these abilities are characteristic of almost all representatives of the named species of fauna, it’s just that in most of them the discharges are small, perceptible only with powerful sensitive devices. They use them to transmit signals to each other - as a means of communication. The strength of the emitted signals allows you to determine who is who in the fish environment, or, in other words, find out the strength of your opponent.
Electric fish They use their special organs to protect themselves from enemies, as weapons to kill prey, and also as locators.
Where is the fish's power plant?
Electrical phenomena in the body of fish have interested scientists involved in natural energy phenomena. The first experiments to study biological electricity were carried out by Faraday. For his experiments, he used stingrays as the most powerful producers of charges.
One thing that all researchers agreed on is that the main role in electrogenesis belongs to cell membranes, which are capable of distributing positive and negative ions in cells, depending on excitation. The modified muscles are connected to each other in series, these are the so-called power plants, and the connective tissues are conductors.
“Energy-producing” bodies can have very different types and locations. So, in stingrays and eels these are kidney-shaped formations on the sides, in elephant fish they are cylindrical threads in the tail area.
As already mentioned, producing current on one scale or another is common to many representatives of this class, but there are real electric fish that are dangerous not only to other animals, but also to humans.
Electric snake fish
The South American electric eel has nothing in common with ordinary eels. It is named simply because of its external resemblance. This long, up to 3 meters, snake-like fish weighing up to 40 kg is capable of generating a discharge of 600 volts! Close communication with such a fish can cost your life. Even if the current does not directly cause death, it will definitely lead to loss of consciousness. A helpless person can choke and drown.
Electric eels live in the Amazon, in many shallow rivers. The local population, knowing their abilities, does not enter the water. The electric field produced by the snake fish diverges over a radius of 3 meters. At the same time, the eel shows aggression and can attack without any particular need. He probably does this out of fear, since his main diet is small fish. In this regard, a living “electric fishing rod” does not know any problems: release the charger, and breakfast is ready, lunch and dinner at the same time.
Stingray family
Electric fish - stingrays - are grouped into three families and number about forty species. They tend not only to generate electricity, but also to accumulate it in order to use it further for its intended purpose.
The main purpose of the shots is to scare away enemies and catch small fish for food. If a stingray releases its entire accumulated charge at one time, its power will be enough to kill or immobilize a large animal. But this happens extremely rarely, since the fish - the electric stingray - after a complete “blackout” becomes weak and vulnerable, it takes time for it to accumulate power again. So stingrays strictly control their energy supply system with the help of one of the parts of the brain, which acts as a relay switch.
The family of stingrays, or electric stingrays, are also called “torpedoes.” The largest of them is the inhabitant of the Atlantic Ocean, the black torpedo (Torpedo nobiliana). This one, which reaches a length of 180 cm, produces the strongest current. And in close contact with it, a person may lose consciousness.
Moresby's ray and Tokyo torpedo (Torpedo tokionis ) - the deepest representatives of their family. They can be found at a depth of 1,000 m. And the smallest among its brothers is the Indian stingray, its maximum length- only 13 cm. A blind stingray lives off the coast of New Zealand - its eyes are completely hidden under a layer of skin.
Electric catfish
In the muddy waters of tropical and subtropical Africa live electric fish - catfish. These are quite large individuals, from 1 to 3 m in length. Catfish do not like fast currents; they live in cozy nests at the bottom of reservoirs. The electrical organs, which are located on the sides of the fish, are capable of producing a voltage of 350 V.
The sedentary and apathetic catfish does not like to swim far from its home; it crawls out of it to hunt at night, but also uninvited guests doesn't like it. He meets them with light electric waves, and with them he gets his prey. Discharges help catfish not only hunt, but also navigate in dark, muddy water. Electric catfish meat is considered a delicacy among the local African population.
Nile dragon
Another African electric representative of the kingdom of fish is the Nile gymnarch, or aba-aba. The pharaohs depicted him in their frescoes. It lives not only in the Nile, but in the waters of the Congo, Niger and some lakes. This is a beautiful “stylish” fish with a long graceful body, from forty centimeters to one and a half meters long. There are no lower fins, but one upper one stretches along the entire body. Beneath it is a “battery” that produces electromagnetic waves of 25 V almost constantly. The head of the gymnarch carries a positive charge, and the tail carries a negative charge.
Gymnarchs use their electrical abilities not only to search for food and location, but also in mating games. By the way, male gymnarchs are simply amazingly fanatical fathers. They do not move away from laying eggs. And as soon as someone gets close to the children, dad will shower the offender with a stun gun so much that it won’t seem like much.
Gymnarchs are very cute - their elongated, dragon-like muzzle and cunning eyes have gained love among aquarists. True, the handsome guy is quite aggressive. Of several fry placed in an aquarium, only one will survive.
sea cow
Large bulging eyes, an ever-open mouth framed by fringe, and an extended jaw make the fish look like an eternally dissatisfied, grumpy old woman. What is the name of an electric fish with such a portrait? family of stargazers. The comparison with a cow is evoked by the two horns on its head.
This unpleasant person most of spends time burying itself in the sand and lying in wait for prey passing by. The enemy will not pass: the cow is armed, as they say, to the teeth. The first line of attack is a long red tongue-worm, with which the stargazer lures naive fish and catches them without even getting out of cover. But if necessary, it will fly up instantly and stun the victim until he loses consciousness. The second weapon for self-defense is poisonous spines located behind the eyes and above the fins. And that's not all! The third powerful weapon is located behind the head - electrical organs that generate charges with a voltage of 50 V.
Who else is electric?
The ones described above are not the only electric fish. The names of those not listed by us sound like this: Peters gnathonema, black knifeworm, mormyra, diplobatis. As you can see, there are a lot of them. Science has made a big step forward in studying this strange ability of some fish, but to this day it has not been possible to completely unravel the mechanism for accumulating high-power electricity.
Do fish heal?
Official medicine has not confirmed that the electromagnetic field of fish has a healing effect. But folk medicine has long used the electric waves of stingrays to cure many diseases of a rheumatic nature. To do this, people specifically walk nearby and receive weak shocks. This is what natural electrophoresis looks like.
Residents of Africa and Egypt use electric catfish to treat severe fever. To increase immunity in children and strengthen their general condition, equatorial residents force them to touch catfish, and also give them water in which this fish swam for some time.
Dominic Statham
Photo ©depositphotos.com/Yourth2007
Electrophorus electricus) lives in dark waters swamps and rivers in northern South America. This is a mysterious predator with complex system electrolocation and capable of moving and hunting in low visibility conditions. Using "electroreceptors" to detect electrical field distortions caused by his own body, he is able to detect potential prey without being detected himself. It immobilizes the victim with a powerful electric shock, strong enough to stun a large mammal such as a horse or even kill a human. With its elongated, rounded body shape, the eel resembles the fish that we usually call the moray eel (order Anguilliformes); however, it belongs to a different order of fish (Gymnotiformes).Fish that can detect electric fields are called electroreceptive, but capable of generating powerful electric field, such as the electric eel, are called electrogenic.
How does an electric eel generate such high electrical voltage?
Electric fish aren't the only ones capable of generating electricity. Virtually all living organisms do this to one degree or another. The muscles in our body, for example, are controlled by the brain using electrical signals. The electrons produced by the bacteria can be used to generate electricity in fuel cells called electrocytes. (see table below). Although each cell carries only a small charge, by stacking thousands of cells in series, like batteries in a flashlight, voltages of up to 650 volts (V) can be generated. If you arrange these rows in parallel, you can produce an electric current of 1 Ampere (A), which gives an electric shock of 650 watts (W; 1 W = 1 V × 1 A).
How does the eel manage to avoid electrocuting itself?
Photo: CC-BY-SA Steven Walling via Wikipedia
Scientists don't know exactly how to answer this question, but some interesting observations may shed light on the problem. First, the eel's vital organs (such as the brain and heart) are located near the head, away from the electricity-producing organs, and are surrounded by fatty tissue that can act as insulation. Skin also has insulating properties, as acne with damaged skin has been observed to be more susceptible to self-stunning by electrical shock.
Secondly, eels are able to deliver the most powerful electric shocks at the moment of mating, without causing harm to the partner. However, if a blow of the same force is applied to another eel not during mating, it can kill it. This suggests that eels have some kind of defense system that can be turned on and off.
Could the electric eel have evolved?
It is very difficult to imagine how this could happen through minor changes, as required by the process proposed by Darwin. If the shock wave was important from the very beginning, then instead of stunning, it would warn the victim of danger. Moreover, in order to evolve the ability to stun prey, the electric eel would have to simultaneously develop a self-defense system. Every time a mutation arose that increased the power of the electric shock, another mutation must have arisen that improved the eel's electrical insulation. It seems unlikely that a single mutation would be sufficient. For example, in order to move organs closer to the head, a whole series of mutations would be required, which would have to occur simultaneously.
Although few fish are capable of stunning their prey, there are many species that use low-voltage electricity for navigation and communication. Electric eels belong to a group of South American fish known as "knife eels" (family Mormyridae) that also use electrolocation and are thought to have evolved this ability along with their South American cousins. Moreover, evolutionists are forced to declare that electrical organs in fish evolved independently of each other eight times. Considering the complexity of their structure, it is striking that these systems could have developed during evolution at least once, let alone eight.
Knives from South America and chimaeras from Africa use their electrical organs for location and communication, and use a number of various types electroreceptors. In both groups there are species that produce electric fields of different complex shapes waves. Two types of knife blades Brachyhypopomus benetti And Brachyhypopomus walteri are so similar to each other that they could be classified as one type, but the first of them produces a constant voltage current, and the second produces an alternating voltage current. The evolutionary story becomes even more remarkable when you dig even deeper. To ensure that their electrolocation devices do not interfere with each other and do not create interference, some species use a special system with the help of which each of the fish changes the frequency of the electrical discharge. It is noteworthy that this system works almost the same (using the same computational algorithm) as the glass knife from South America ( Eigenmannia) and African fish aba-aba ( Gymnarchus). Could such a system for eliminating interference have independently evolved in two separate groups of fish living on different continents?
Masterpiece of God's creation
The energy unit of the electric eel has eclipsed all human creations with its compactness, flexibility, mobility, environmental safety and the ability to self-heal. All parts of this apparatus are perfectly integrated into the polished body, which gives the eel the ability to swim with great speed and agility. All the details of its structure - from tiny cells that generate electricity to the most complex computing complex that analyzes the distortions of the electric fields produced by the eel - point to the plan of the great Creator.
How does an electric eel generate electricity? (popular science article)
Electric fish generate electricity much like the nerves and muscles in our body. Inside electrocyte cells there are special enzyme proteins called Na-K ATPase pump sodium ions across the cell membrane and absorb potassium ions. (‘Na’ is the chemical symbol for sodium and ‘K’ is the chemical symbol for potassium. ‘ATP’ is adenosine triphosphate, an energy molecule used to operate the pump). An imbalance between potassium ions inside and outside the cell results in a chemical gradient that pushes potassium ions out of the cell again. Likewise, an imbalance between sodium ions creates a chemical gradient that draws sodium ions back into the cell. Other proteins embedded in the membrane act as potassium ion channels, pores that allow potassium ions to leave the cell. As positively charged potassium ions accumulate outside the cell, an electrical gradient builds up around the cell membrane, causing outer part the cell has a more positive charge than its interior. Pumps Na-K ATPase (sodium-potassium adenosine triphosphatase) are designed in such a way that they select only one positively charged ion, otherwise negatively charged ions would also flow in, neutralizing the charge.
Most of the electric eel's body consists of electrical organs. The main organ and the Hunter's organ are responsible for the production and accumulation of electrical charge. Sachs's organ produces a low-voltage electrical field that is used for electrolocation.
The chemical gradient acts to push potassium ions out, while the electrical gradient pulls them back in. At the moment of balance, when chemical and electrical forces cancel each other out, there will be about 70 millivolts more positive charge on the outside of the cell than on the inside. Thus, a negative charge of -70 millivolts appears inside the cell.
However more Proteins embedded in the cell membrane provide sodium ion channels - these are pores that allow sodium ions to re-enter the cell. Normally these pores are closed, but when the electrical organs are activated, the pores open and positively charged sodium ions flow back into the cell under the influence of a chemical potential gradient. In this case, balance is achieved when a positive charge of up to 60 millivolts accumulates inside the cell. There is a total voltage change from -70 to +60 millivolts, and this is 130 mV or 0.13 V. This discharge occurs very quickly, in about one millisecond. And since approximately 5000 electrocytes are collected in a series of cells, up to 650 volts (5000 × 0.13 V = 650) can be generated due to the synchronous discharge of all cells.
Na-K ATPase (sodium-potassium adenosine triphosphatase) pump. During each cycle, two potassium ions (K+) enter the cell, and three sodium ions (Na+) leave the cell. This process is driven by the energy of ATP molecules.
Glossary
An atom or molecule that carries an electrical charge due to an unequal number of electrons and protons. An ion will have a negative charge if it contains more electrons than protons, and a positive charge if it contains more protons than electrons. Potassium (K+) and sodium (Na+) ions have a positive charge.
Gradient
A change in any value when moving from one point in space to another. For example, if you move away from the fire, the temperature drops. Thus, the fire generates a temperature gradient that decreases with distance.
Electrical gradient
Gradient of change in the magnitude of electric charge. For example, if there are more positively charged ions outside the cell than inside the cell, an electrical gradient will flow across the cell membrane. Because like charges repel each other, the ions will move in a way that balances the charge inside and outside the cell. The movements of ions due to the electrical gradient occur passively, under the influence of electrical potential energy, and not actively, under the influence of energy coming from external source, for example from an ATP molecule.
Chemical gradient
Chemical concentration gradient. For example, if there are more sodium ions outside the cell than inside the cell, then a chemical gradient of sodium ion will flow across the cell membrane. Because of the random movement of ions and the collisions between them, there is a tendency for sodium ions to move from higher concentrations to lower concentrations until a balance is established, that is, until there are equal numbers of sodium ions on both sides of the membrane. This happens passively, as a result of diffusion. The movements are due to the kinetic energy of the ions, rather than energy received from an external source such as an ATP molecule.
Speaking about the possibility of fish using the Earth’s magnetic field for navigation purposes, it is natural to raise the question of whether they can perceive this field at all.
In principle, both specialized and non-specialized systems can respond to the Earth’s magnetic field. At present, it has not been proven that fish have specialized receptors sensitive to this field.
How do non-specialized systems perceive the Earth's magnetic field? More than 40 years ago, it was suggested that the basis of such mechanisms could be induction currents arising in the body of fish when they move in the Earth’s magnetic field. Some researchers believed that during migrations fish use electric induction currents resulting from the movement (flow) of water in the Earth's magnetic field. Others believed that some deep-sea fish use inductive currents that arise in their bodies when moving.
It is calculated that at a fish movement speed of 1 cm per second per 1 cm of body length, a potential difference of about 0.2-0.5 μV is established. Many electric fish, which have special electroreceptors, perceive electric field strengths of even lower magnitude (0.1-0.01 μV per 1 cm). Thus, in principle, they can be oriented towards the Earth’s magnetic field during active movement or passive drift (drift) in water flows.
Analyzing the graph of the threshold sensitivity of the gymnarch, the Soviet scientist A. R. Sakayan concluded that this fish senses the amount of electricity flowing in its body, and suggested that weakly electric fish are able to determine the direction of their path along the Earth’s magnetic field.
Sakayan views fish as a closed electrical circuit. When a fish moves in the Earth's magnetic field, an electric current passes through its body as a result of induction in the vertical direction. The amount of electricity in the body of a fish when it moves depends only on the relative position in space of the direction of the path and the line of the horizontal component of the Earth's magnetic field. Therefore, if a fish responds to the amount of electricity flowing through its body, it can determine its path and its direction in the Earth's magnetic field.
Thus, although the question of the electro-navigation mechanism of weakly electric fish has not yet been fully clarified, the fundamental possibility of their use of induction currents is beyond doubt.
The vast majority of electric fish are “sedentary”, non-migrant forms. In migrant non-electric fish species (cod, herring, etc.), electrical receptors and high sensitivity to electric fields have not been found: usually it does not exceed 10 mV per 1 cm, which is 20,000 times lower than the intensity of electric fields caused by induction. The exception is non-electric fish (sharks, rays, etc.), which have special electroreceptors. When moving at a speed of 1 m/s, they can perceive an induced electric field of 0.2 μV per 1 cm. Electric fish are about 10,000 times more sensitive to electric fields than non-electric fish. This suggests that non-electric fish species cannot navigate the Earth's magnetic field using induction currents. Let us dwell on the possibility of fish using bioelectric fields during migration.
Almost all typically migratory fish are schooling species (herring, cod, etc.). The only exception is the eel, but when entering the migratory state, it undergoes a complex metamorphosis, which may affect the generated electric fields.
During the migration period, fish form dense, organized schools moving in a certain direction. Small schools of these same fish cannot determine the direction of migration.
Why do fish migrate in schools? Some researchers explain this by the fact that, according to the laws of hydrodynamics, the movement of fish in schools of a certain configuration is facilitated. However, there is another side to this phenomenon. As already mentioned, in excited schools of fish the bioelectric fields of individual individuals are summed up. Depending on the number of fish, the degree of their excitation and the synchronism of radiation, the total electric field can significantly exceed the volumetric dimensions of the school itself. In such cases, the voltage per fish can reach such a value that it is able to perceive the electric field of the school even in the absence of electroreceptors. Consequently, fish can use the school's electric field for navigation purposes due to its interaction with the Earth's magnetic field.
How do non-schooling migrant fish - eels and Pacific salmon, which make long migrations - navigate in the ocean? The European eel, for example, becoming sexually mature, moves from rivers to the Baltic Sea, then to the North Sea, enters the Gulf Stream, moves in it against the current, crosses Atlantic Ocean and comes to the Sargasso Sea, where it breeds at great depths. Consequently, the eel cannot navigate either by the Sun or by the stars (birds use them to navigate during migrations). Naturally, the assumption arises that since the eel travels most of its journey while in the Gulf Stream, it uses the current for orientation.
Let's try to imagine how an eel orients itself while inside a multi-kilometer layer of moving water (chemical orientation is excluded in this case). In the water column, all the streams of which move in parallel (such flows are called laminar), the eel moves in the same direction as the water. Under these conditions, its lateral line - an organ that allows it to perceive local water flows and pressure fields - cannot work. In the same way, when floating along a river, a person does not feel its flow if he does not look at the shore.
Perhaps the sea current does not play any role in the eel’s orientation mechanism and its migration routes coincidentally coincide with the Gulf Stream? If so, what are the signals? environment does the eel use what guides its orientation?
It remains to be assumed that eel and Pacific salmon use the Earth's magnetic field in their orientation mechanism. However specialized systems for its perception in fish was not found. But in the course of experiments to determine the sensitivity of fish to magnetic fields, it turned out that both eels and Pacific salmon have exceptionally high sensitivity to electric currents in water directed perpendicular to the axis of their body. Thus, the sensitivity of Pacific salmon to current density is 0.15 * 10 -2 μA per 1 cm 2, and the sensitivity of eels is 0.167 * 10 -2 per 1 cm 2.
The idea was expressed that eels and Pacific salmon use geoelectric currents created in ocean water by currents. Water is a conductor moving in the Earth's magnetic field. The electromotive force resulting from induction is directly proportional to the strength of the Earth's magnetic field at a given point in the ocean and a certain current speed.
A group of American scientists carried out instrumental measurements and calculations of the magnitudes of emerging geoelectric currents along the eel’s route. It turned out that the densities of geoelectric currents are 0.0175 μA per 1 cm 2, i.e., almost 10 times higher than the sensitivity of migrant fish to them. Subsequent experiments confirmed that eels and Pacific salmon are selective towards currents with similar densities. It became obvious that eel and Pacific salmon can use the Earth's magnetic field and sea currents for their orientation during migrations in the ocean due to the perception of geoelectric currents.
The Soviet scientist A.T. Mironov suggested that when orienting fish, they use telluric currents, which he first discovered in 1934. Mironov explains the mechanism of occurrence of these currents by geophysical processes. Academician V.V. Shuleikin connects them with electromagnetic fields in space.
Currently, the work of employees of the Institute of Terrestrial Magnetism and Radio Wave Propagation in the Ionosphere of the USSR Academy of Sciences has established that the constant component of the fields generated by telluric currents does not exceed a strength of 1 µV per 1 m.
Soviet scientist I. I. Rokityansky suggested that since telluric fields are inductive fields with different amplitudes, periods and directions of vectors, fish tend to go to places where the magnitude of telluric currents is less. If this assumption is correct, then during the period of magnetic storms, when the intensity of telluric fields reaches tens - hundreds of microvolts per meter, fish should move away from the shores and from shallow places, and, consequently, from fishing grounds to deep-sea areas, where the magnitude of telluric fields is less. Studying the relationship between fish behavior and magnetic activity will make it possible to develop methods for predicting their fishing aggregations in certain areas. Employees of the Institute of Terrestrial Magnetism and Radio Wave Propagation in the Ionosphere and the Institute of Evolutionary Morphology and Animal Ecology of the USSR Academy of Sciences carried out work in which a certain correlation was identified when comparing Norwegian herring catches with magnetic storms. However, all this requires experimental verification.
As mentioned above, fish have six signaling systems. But don’t they use some other sense that is not yet known?
In the USA in the newspaper “Electronics News” for 1965 and 1966. a message was published about the discovery by W. Minto of special “hydronic” signals of a new nature, used by fish for communication and location; Moreover, in some fish they were recorded at a great distance (in mackerel up to 914 m). It was emphasized that “hydronic” radiation cannot be explained electric fields, radio waves, sound signals or other previously known phenomena: hydronic waves propagate only in water, their frequency ranges from fractions of a hertz to tens of megahertz.
It was reported that the signals were discovered by studying the sounds made by fish. Among them are frequency-modulated, used for location, and amplitude-modulated, emitted by most fish and intended for communication. The former resemble a short whistle, or “chirp,” while the latter resemble a “chirp.”
W. Minto and J. Hudson reported that hydronic radiation is characteristic of almost all species, but this ability is especially strongly developed in predators, fish with underdeveloped eyes and in those that hunt at night. Orientation signals (location signals) are emitted by fish in new environment or when exploring unfamiliar objects. Communication signals are observed in a group of individuals after the return of fish that have been in an unfamiliar environment.
What prompted Minto and Hudson to consider “hydronic” signals to be a manifestation of a previously unknown physical phenomenon? According to them, these signals are not acoustic because they can be perceived directly by the electrodes. At the same time, “hydronic” signals cannot be classified as electromagnetic oscillations, according to Minto and Hudson, since, unlike ordinary electrical ones, they consist of pulses that are not constant and last several milliseconds.
However, it is difficult to agree with such views. In electric and non-electric fish, signals are very diverse in shape, amplitude, frequency and duration, and therefore the same properties of “hydronic” signals do not indicate their special nature.
The last “unusual” feature of “hydronic” signals - their propagation over a distance of 1000 m - can also be explained on the basis of well-known principles of physics. Minto and Hudson did not conduct laboratory experiments on a single individual (data from such experiments indicate that the signals of individual non-electric fish travel over short distances). They recorded signals from schools and schools of fish in sea conditions. But, as already mentioned, in such conditions the intensity of the bioelectric fields of fish can be summed up, and the single electric field of the school can be detected at a considerable distance.
Based on the above, we can conclude that in the works of Minto and Hudson it is necessary to distinguish between two sides: the factual one, from which it follows that non-electric fish species are capable of generating electrical signals, and the “theoretical” - an unproven assertion that these discharges have a special, so-called hydronic nature.
In 1968, the Soviet scientist G. A. Ostroumov, without going into the biological mechanisms of generation and reception of electromagnetic signals by marine animals, but based on the fundamental principles of physics, made theoretical calculations that led him to the conclusion that Minto and his followers were mistaken in attributing special physical nature of “hydronic” signals. In essence, these are ordinary electromagnetic processes.
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Many readers of the site about animals know that there are fish that have the ability to give electric shocks (literally), but not everyone knows how this is done. We propose to consider two of the most famous marine representatives that produce current: the electric stingray and the electric eel. You will learn:
- is the current of these electric fish dangerous for humans;
- how the organs that produce electricity in stingrays and eels are structured;
- how stingrays and eels hunt and catch prey;
- how live fish are associated with the New Year holiday.
Electric stingray - living battery
Electric rays are mostly small - from 50 to 60 cm, but there are some individuals that reach a length of 2 m. Small representatives of these fish create a slight electrical charge, and in turn large rays carry out discharges of 300 volts. The organs of an individual that produce current make up 1/6 of the body and are very developed. They are located on both sides - they occupy the space between the fin of the chest and the head, and can be viewed from the dorsal and abdominal parts.
The internal organs of fish that produce electricity have the following structure. A certain number of columns that make up the electric plates and the bottom of the plate, like the entire organ, carries a negative charge, and the top is positively charged.
When hunting, the stingray strikes prey by wrapping its fins around it, where the organs that produce electricity are located. During this process, an electrical charge is applied and the prey is electrocuted to death. Stingray is similar to a battery. If he uses the entire charge, then he will need a few more to “charge” again.
A ramp without a charge is safe, however, if it has a charge, then a person can be seriously injured by a strong electrical discharge. No fatal incidents have been identified, although those who touch the stingray may experience low blood pressure, heart rhythm disturbances, spasms, and swelling of local tissues in the affected area. The stingray is inactive and mainly lives at the bottom, so in order not to meet it in aquatic environment, you need to pay attention when in shallow water.
In ancient Roman times, on the contrary, electrical discharges were (and are now recognized in medicine) as healing. It was believed that electric shock could relieve headaches and relieve gout. Even today, on the shores of the Mediterranean, older people deliberately walk barefoot in shallow water to relieve rheumatism and gout with electric shocks.
An electric eel lit up the lights on the Christmas tree.
And now the note, although about fish, concerns such a holiday as New Year! It would seem how it fits live fish and a Christmas tree? Here's how. Read on.
Most representatives from the electric eel group are from 1 to 1.5 m long, but there are species that reach three meters. In such individuals, the impact force reaches 650 volts. People electrocuted in water may lose consciousness and drown. The electric eel is one of the most dangerous representatives of the Amazon River. The eel emerges approximately once every 2 minutes to fill its lungs with air. He is very aggressive. If you approach an eel at a distance of less than three meters, it prefers not to take cover, but to immediately attack. Therefore, people who see an eel closely should quickly swim away as far as possible.
The organs of the eel responsible for current have a similar structure to the organs of the stingray., but have a different location. They represent two elongated sprouts that have an oblong appearance and make up 4/5 of the eel’s body as a whole and have a mass that occupies almost 1/3 of the weight of the body. The front part of the eel carries a positive charge, and the back, accordingly, a negative one. As eels age, their vision decreases; it is because of this that they strike their prey by emitting weak electric shocks. The eel does not attack prey; a powerful charge is enough for it to kill all small fish from electric shock. The eel approaches its prey when it is already dead, grabs it by the head, and then swallows it.
Eels can often be seen in an aquarium, as they get used to life relatively quickly. artificial conditions. Of course, keeping such a fish at home is more difficult than breeding newts. In order to exhibit their capabilities, a lamp is attached to the tank and the wires are lowered into the water. During feeding, the light comes on. In Japan, in 2010, an experiment was carried out: a Christmas tree was lit using a current coming from an eel, which was in a special container and emitted current. Even the eel and its electric current can be useful if the unique natural abilities of this fish are channeled in the right direction.
Of all vertebrates, only fish are able to produce enough electrical energy to paralyze or even kill a person. Electrical organs serve fish for defense, orientation, hunting and possibly communication. About two hundred and fifty species of fish are capable of generating electrical energy; however, only electric eels accumulate a charge so powerful that it can serve as a weapon against humans ( Electrophorus electricus), living in South America and electric stingrays, belonging to the family Тorpedinidae.
How animals generate such powerful pulses of electrical energy remains a mystery to scientists, but the nature of animal electricity is quite clear. Electrical energy arises in the body of any animal - including humans. Electrical impulses travel along nerve fibers and send signals to brain cells and other cells about various phenomena. Even reading these pages, reader, generates electrical signals; but in electric eels and some stingrays the energy accumulates so much that it is used as a weapon against other fish and animals. Let's look at how it is formed.
Humanity learned that animal tissue generates electricity in 1791, when Luigi Galvani, professor of anatomy at the University of Bologna, discovered that the nervous and muscle tissue The frog's legs respond to electric current. Over time, scientists discovered that the pulses sending signals across nervous system humans, are of an electrochemical nature. To simplify the picture, we can say that nerve signals are the movement of ions, that is, charged particles through the membranes of nerve cells. In a state of rest or inactivity of a cell, its shell has a negative potential, since negatively charged ions accumulate from inside the cell; however, there are both positive and negative ions outside the cell, and among them are sodium ions, which carry a positive charge. When a nerve cell sends a signal, its membrane changes polarity, and sodium ions penetrate through it into the cell, changing its potential to positive. Having returned to its normal state, the cell gets rid of sodium ions using a mechanism, the “device” of which is unknown; Scientists call it the “sodium pump” because it seems to pump sodium ions out of the cell.
When the cell transmits the signal, the “pump” stops working. Sodium and potassium ions are attracted to each other, exchanging charges and neutralizing the cell's electrical potential. Tiny discharges travel up a nerve fiber extending from the cell, exciting an electrical field in the surrounding tissue and fluid. The signal, or nerve impulse, travels along the nerve fiber until it reaches a point where it branches into branches called nerve endings. The endings penetrate the space separating one nerve cell from another. This space between two adjacent cells of nerve tissue is called a synapse.
At some point, the nerve impulse traveling to the muscle reaches the synapse, at opposite side which the muscle fiber cell is located. This point, called the neuromuscular junction, plays a critical role in generating electricity in fish. When a nerve impulse appears at the neuromuscular junction, a secretion is released around the nerve endings. chemical substance, called acetylcholine. Leaking from a nerve cell to a muscle cell, acetylcholine transmits an impulse to the muscle fiber, depolarizing it and thereby causing an electrical discharge. It is also assumed that another function of acetylcholine is to stop the action of the “sodium pump” in the cell, which allows ions to penetrate the cell membrane.
Typically, an electrical signal causes a muscle to contract, which is reflected in various movements of the animal's body. However, some muscles in fish have lost the ability to contract. The nerve endings going to these muscles lie very densely in the area of the neuromuscular junction, and the fibers of the muscle cells grow so much that they form something like a living electrode.
The electrical organs of fish such as electric eels and electric rays are made up of several similar "electrodes". When they are all discharged, a high-power electric current occurs. The discharge is controlled by a bundle of nerves, which in the electric eel departs from the spinal cord, and in the electric stingray - from the brain.
Electric stingrays, which live in both temperate and tropical zones, are capable of creating voltages of up to 50 volts and higher on their “electrodes”; this is enough to kill the fish and crustaceans that stingrays feed on. The electric stingray looks like a flexible pancake with a long and thick tail. When hunting, the stingray rushes at the prey with its whole body and “hugs” it with its “wings”, at the ends of which there are electrical organs. The hug closes, the “electrodes” are discharged - and the stingray kills its victim with an electric discharge.
The largest of the electric stingrays is Torpedo nobiliana, inhabitant of the waters of the North Atlantic; it reaches 1.8 meters in length, weighs about 100 kilograms and is capable of creating a potential difference of 200 volts - this is enough to kill any animal caught in the water nearby. The special effectiveness of electric discharge in water is explained by the fact that water is a good conductor of electric current.
The electric stingray is mentioned in many legends that have come down to us from time immemorial; dream interpreters believed that it foreshadows an imminent misfortune. The Greeks and Romans knew that the stingray owned a source of some kind strange energy, and since electricity was not known then, it was believed that its source was some unknown substance. There was another belief - that a stingray caught on a bronze hook kills a fisherman who has abandoned the tackle, and death occurs from blood clotting.
In ancient times, stingrays were used for treatment through shock. Healers placed small stingrays on the heads of patients suffering from headaches and other ailments; Stingray was believed to have healing properties.
An electric eel that generates a current of 650 volts—several times the voltage that even the largest stingray can produce—could kill anyone in the water nearby. The electric eel has little in common with other eels; it is related to the knifefish and lives in rivers. The electric eel reaches a length of 2.7 meters and a thickness of about 10 centimeters. Four-fifths of its body is occupied by three electrical organs, and only one-fifth of its length is accounted for by other organs that perform such important vital functions as breathing, digestion, reproduction and others.
The waters in which the electric eel lives are poor in oxygen, but this does not bother the eel: it has learned to breathe atmospheric oxygen as well. Numerous blood vessels in its mouth are able to absorb oxygen, and the eel captures air, rising to the surface of the water.
A young electric eel can see well, but as it ages, its vision deteriorates sharply. This does not particularly bother the eel, because in the dark, muddy water where it usually lives, the eyes are of little use anyway. The same electrical organs help the eel search for prey: it emits relatively weak electrical impulses, the voltage of which does not exceed 40 - 50 volts; these low-voltage discharges help him find small sea creatures, which the eel feeds on. In addition, electric eels are probably able to perceive each other's electrical discharges - in any case, when one of them paralyzes the prey with an electric shock, other eels rush to the prey.
Electric eels adapt well to life in captivity and can often be seen in aquariums; Usually the aquarium is equipped with some kind of electrical appliance to demonstrate the unique abilities of the eel, for example, with a lamp to which wires lead from two electrodes lowered into the water. When pieces of food or small fish are thrown into the aquarium, the lamp lights up because, sensing prey, the eel begins to generate electrical discharges in the water. The aquarium can also be equipped with sound amplifiers, and then visitors will hear static noises accompanying the current discharges generated by the eel.
Handling an electric eel is quite dangerous. At the London Zoo, an eel once gave a severe electric shock to the attendant who was feeding it. Another eel began to generate electrical discharges when it was carried into metal box, and the attendant had to throw the box on the ground. But only with direct contact the eel's blow is fatal; however, a swimmer caught in the water near the discharge site may drown while in shock.
The eel's ability to generate huge amounts of electricity has attracted the attention of biologists and doctors for more than a century. During the Second World War, the military, including the American ones, became interested in it: two years after the United States entered the war, two hundred electric eels caught in South America were delivered to New York. The Bronx Zoo built twenty-two wooden pools for them. Eels were used in experiments to study the effects of nerve gases, which block the transmission of nerve impulses and thus can stop the functioning of the heart, lungs and other vital organs. The essence of the action of gases is that they prevent the breakdown of acetylcholine after it stops the “sodium pump” of the nerve cell. Typically, acetylcholine is broken down in the body immediately after it has performed its function; The breakdown process is controlled by an enzyme called cholinesterase. Nerve gases precisely interfere with the action of this enzyme.
The electric organs of the eel contain a large amount of cholinesterase, which is also highly active; That’s why military specialists needed electric eels brought to the Bronx Zoo: they served as a source of the enzyme needed to study the nerve-paralytic effects of poisonous gases. Most zoo workers only learned after the war why so many electric eels were kept in the basements of the lion enclosure.
Fish make up a minority of the inhabitants of the world's oceans; a much larger part of its inhabitants are invertebrates, and it is among them that there are the most miniature and harmless aquatic animals, and the most huge and dangerous.
In adventure films and novels set in the seas of the southern hemisphere, a giant clam often appears Tridacna gigas, depicted as a kind of living trap, a trap waiting for an unwary swimmer. In fact, this giant feeds on plankton and does not at all have the enormous strength that is usually attributed to it - even if the size of its shell really reaches 1.2 meters, and the weight of the mollusk itself is 220 kilograms. There is not a single documented case of a person dying from a collision with Tridacna gigas, however, even such authoritative sources as the Marine Science magazine published by the US Navy warn the reader about the danger this mollusk poses to a scuba diver. However, it is unlikely that a mollusk that accidentally closes its valves around a human leg will hold it; rather, he will try to get rid of inconvenient prey.
