It turns out that fears remember not only people were fears have even more power over such ferocious predators like sharks. These marine killer afraid specific electrical discharges. This behaviour is formed already in embryos - a kind of electric field akulenok can understand, there are any number predator, or not.

If for terrestrial animals of the greatest importance at orientation in space have a smell, sound and color, that the inhabitants of the seas rely more on electrosubstation. Especially well this feeling is developed in fish - body sides of these vertebrate hosts a number of electroreception called the touchline. And the sharks there and special ampoules of Lorenzini on the head, too, can feel the electric field.

Measuring characteristics of electric discharges, fish can learn a lot: and to what depth it is, and how dirty the water around, and even whether someone is near. Moreover, feeling an electric field, it clearly recognizes that each comes nearer to it or foe. The fact that the characteristics of the discharges depend on specific substances allocates water resident in the environment (which interact with ions dissolved in water and thereby produce electric fields). You understand that these substances are all different, so you might say, they are a kind of species "ID".

By the way, and predators often helps to find a victim it is emitted by her electric discharges. Thus, it was found that the shark or scat can find hidden, Saryusz in silt or sand extraction with the help of the above-mentioned vials of Lorenzini. By the way, many victims know about this too and so take precautions. For example, funny fish, parrot (Scaridae), settling in for the night, surrounded by a dense cocoon of mucus, through which prevents the allocation of substances from their bodies, and, consequently, the emergence of the electric field.

However, even fierce predators can perceive the electric field as an alarm signal. A recent study showed that young leopard sharks and American summer rays, felt him freeze on the spot - just like gophers who heard suspicious sound. It seemed to biologists quite strange as these fish, like, especially not to fear anyone. However, they always react to signals, which are formed when approaching them fish, whose size is comparable to their own.

And now scientists from the University of Western Australia decided to solve the riddle. They suggested that in this case the researchers dealt with innate behavioral reaction - sharks learn afraid electric fields while still embryos. In order to test this hypothesis, biologists conducted several experiments with embryos by korichnevaya leopard sharks (Chiloscyllium punctatum) is a medium - sized predator that way of life is very similar to freshwater catfish and is not dangerous for humans.

This fish, like most of her relatives thought, lays eggs, enclosed in a hard shell. Therefore, in order to be able to breathe, a small shark in the egg actively wiggles his tail, strengthening the exchange of water between your "haven"and the external environment - that is, as if "air space". However, with the water come out of the substance that creates an electric field. In addition, the work of the small muscles of the predator makes it even more powerful. It turns out that the embryo when breathing unmask himself as a predator, feeling an electric field will quickly find the clutch and eat all the eggs.

The results of the experiments have shown that if a small shark suddenly felt strange electric field (as we remember, approaching predator also it generates), it for some time ceased to move the tail, and its gills. Thus, in order not to find herself, she had to literally hold your breath. And what is interesting - if it was a signal from a very large fish, "respiratory" pause embryo was short, and if the one whose dimensions are comparable with adult shark is long. However, this is quite understandable - the big fish will not spend the time to find a very small eggs.

But that's not all. Repeating a series of experiments have already hatched and grown sharks, the researchers found that they awhile remember this alarming electrical signal. However, not particularly long - after a few months he never makes them strong stress response. However, even after a year sharks still stop for a few seconds, feeling the discharge of which they are so much afraid, being quite small. That is, and these predators are a kind of childish fears, from which they can't get most of his life.

Having established this, biology suggested that, perhaps, you can create some devices, generating an electric field is similar to that of "childhood nightmares", could turn away from the beaches of representatives dangerous shark species. However, in order to create them, you need to figure out which bits are afraid white, tiger and other sharks, gives people a lot of trouble. And how long they remember their infant fears - these can be the predator much less prone to introspection than leopard sharks...