On closer examination, the evolutionary advantages of various types of fish jellyfish are not as obvious. So if one takes into account the characteristics of the structure of the body, and the way to make the hunt jellyfish closest competitors fish feed on plankton, and even the slightest imbalance between them established over the years with the emergence of life in the ocean jellyfish quickly gain the upper hand.
At our first meeting, it looks like real jellyfish predators do not compete with the fish. Fish quickly and actively move, can see chosen prey and chase it, this feature is not available jellyfish. However, in some parts of the oceans there is a paradoxical situation: sedentary jellyfish supplant fish feeding on plankton. An international team of zoologists, comparing the advantages and disadvantages of jellyfish with a mathematical model, concluded that we underestimate them.
To conduct the study, information was collected on more than 600 species of jellyfish and fish. Scientists consider features such as speed, efficiency, energy metabolism, body size, and more. The result was that the agility and speed of the fish on its effectiveness so do not give a strong advantage to the class organization of jellyfish. Indeed, the last swim slowly, but on the other hand, they spend less energy. Jellyfish can hunt effectively even in total darkness, which can not possess sight fish.
A large body of jellyfish, in fact, is a fragile gelatinous mass consisting of organic matter, greatly diluted with water. 96 percent of the water contained in the body, and the special stinging cells of jellyfish do not attractive prey for other predators. Finally, a significant body size can cover a large area, and the special pulsating movements promote infiltration of water through a number of tentacles. Hectic and active hunting jellyfish prefer, we can say, direct contact with the chosen victim and increase its size.
Of course, both the jellyfish can not prevail over the more advanced fish, but they may take fish territories where their condition deteriorated. Depletion of fish stocks, caused by heavy fishing off the coast of Japan, the Mediterranean and the Black Sea, in the north-eastern United States, has shifted the balance in favor of jellyfish. According gelatinous predators virtually nothing to press, such as sardines or anchovies from the ocean. In connection with this, as the authors point out the study, one must be careful with the intervention in the biological balance in the ocean: jellyfish are closely watching each step taken, and not miss the opportunity to leave the sea completely without fish.