Jellyfish - the most fascinating creatures of the sea

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Post on 08-Aug-2015




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<ol><li> 1. Jellyfish - the most fascinating creatures of the seaMany people, including Francesco Corallo are intrigued by the variety of jellyfish that are found in the seas; There are over 4,000 species in the world, each of which varies in terms of color, size, shape, behavior and defense mechanism. These variations have been developed over many millennia, in fact, scientists estimate that the jellyfish have existed for at least 650 million years.'Scyphozoa' is the term used to describe the type of jellyfish that most of us know. These creatures have what is known as a 'form a jellyfish', with a large transparent body, to which are attached several tentacles. Most jellyfish do not hunt for food, but rather adopt a passive approach, remaining suspended in an area of the ocean, feeding on algae and small fish that pass between their tentacles. There are, </li><li> 2. however, some species that prefer to hunt for food; these creatures use their tentacles to capture fish larvae and copepods.Each tentacle is composed of specialized cells called nematocysts, which contain microscopic spears full of poison. When the jellyfish detects its prey, spears are thrown from the nematocysts in the tissue of the prey, releasing toxins that can either paralyze you kill the creature. This whole process is extremely rapid, and requires only a fraction of a second.While the color, the shape and size of the jellyfish may vary from one species to another, all share the same basic physical structure. This includes the gastro- vascular cavity, which serves as the digestive system, together with three protective layers (consisting of mesoglea, the ectoderm and endoderm), the tentacles and mouth. Some species - in particular those found in the depths' of seaside- have additional authorities, known as' eyespots', which are sensitive to light. These allow the jellyfish to distinguish between the ocean floor and the surface of the water.Many people, including Francesco Corallo , dealing with environmental pollution and 'impact it has on marine biodiversity. Although the number of many marine species has declined in recent years, this has not been the case for the jellyfish, in fact, because of climate change and the nutrients that form in polluted waters, the population of jellyfish and 'in sharply increased. This has had a negative impact on other marine animals, because more and more jellyfish are competing with them for food resources. This, in turn, is putting particular pressure on the fisheries sector. </li></ol>