All the jellyfish '' Bite '', because all have knidokyttara secreting toxic substances. jellyfish but call, Only a few species of jellyfish, as in contact with the man's cause unpleasant and painful to feel. Of the total 250 species of jellyfish, only the 70 items are jellyfish and dangerous' when we come in contact. The danger lurking in their tentacles hanging from the transparent gelatinous body and their bell-shaped or umbrella. Each tentacle has hundreds knidokyttara and nimatokysteis, containing a long, coiled thread. When irritated the nimatokysti, thread thrown to the victim, like a small harpoon, leaving the target amount of a neurotoxin. This toxic substance is intended either to protect from jellyfish enemies, or paralyze the prey (plankton and other small marine organisms) for food. This poison can cause simple itching, erythroderma, marked signs of pain in the skin, allergy sufferers.

The jellyfish and jellyfish live in seas and oceans, and freshwater (other species adapted to the conditions there), are not indicators of pollution, while withstanding beaches and in shallow coastal waters, the currents of the sea surface, which depend on a 3500 measure, while usually find most of the high seas, but transported by winds. Most jellyfish and jellyfish are highly agile, although usually lured by the currents of the sea, They have the ability to move autonomously, gently, vibrations. A jellyfish can travel several kilometers a day. This, combined with the enormous proliferation of jellyfish in all seas and oceans, makes a major threat to some marine creatures, but for man. the gelatinous, transparent body makes impossible their detection by satellites or sonar, as with schools of fish. Consequently, It is almost impossible to forecast abundance and appearance. And, since jellyfish hardly survive in aquariums, to study closely, the available scientific evidence is scarce on details of their life cycle.

The jellyfish encountered most often in Greek seas is known as ‘'Pelagia fluoresces at night” (Pelagia noctiluca), the only jellyfish which in our region is and jellyfish, or “Chrysalis the gold-trimmed” (Aurelia aurita), The brown-mustard jellyfish the “Kotyloriza with tubercles” (Cotylorhiza tuberculata) resembling a fried egg, the great blue jellyfish (Rhizostoma pulmo).

Jellyfish are planktonic organisms and, like all organizations of this kind, They do not swim but moved drift from sea currents. This explains to a degree the differences in the presence of their populations from sea to sea. Because their movement is very weak, They can not go contrary currents, as with fish. The body of jellyfish and jellyfish consists by up 94%-98% from water. Jellyfish spawn in relatively warm waters usually from spring to autumn, with interruption during the winter months. In recent years, however,, with mild winters and the warm spring and autumn months, the temperature of the Mediterranean waters almost never drops below 14 Celsius degrees, prolonging their breeding season. Some even argue that, if climate change continues at the same rate, We will soon arrive to see jellyfish in the Mediterranean during’ Throughout the year.

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