The jellyfish is an invertebrate and one of the most fascinating marine animal. They are found in the waters of all the oceans of the world and are known to have existed on earth for millions of years. The jellyfish gets its name, from the gelatinous substance that forms the main bulk of its bell shaped body. This substance is known as mesogloea, and is packaged between two layers of cells, which form the outer covering. The density of this substance will vary in density in the different species of jellyfish. These inhabit the ocean at different depths and also found in waters with different temperatures.

From the beginning mankind has had an urge to know more about these strange creatures, and scientists have been known to study them since the 1800's. In early 1900's with the development of technology, marine biologists were able to investigate the behaviour of the jellyfish in its natural environment. In the 1940's biologists were able to observe closely, jellyfish at a depth of 30 meters, with the help of scuba equipment. Later in the 1950's the remotely operated submersible vehicles, gave a tremendous boost to investigations on deep dwelling jellyfish. Later with more sophisticated machinery, scientists were able to collect jellyfish alive without damaging their delicate bodies and transport them onto a ship.

Cnidarians and Ctenophores are the two groups into which the different jellyfish are divided into. The bell shaped jellyfish which is the most familiar, and known scientifically as Medusae, falls under the Cnidarians grouping. These jellyfish expand and contract their bodies, like the action of an umbrella opening and closing, to swim in the ocean. The medusa propels itself bell first, when it forces water out from beneath its body with the jet action. Although the medusae do not have a brain, they are efficient predators, and are able to sense their prey with their tentacles. The tentacles are covered with thousands of stinging cells called nematocysts. When a prey comes in contact with the tentacles, the nematocysts are fired and a venom is injected into the prey by tiny barb-like harpoons. The venom can either paralyse or kill the prey, depending on its size. Only a couple of types of jellyfish is deadly to humans and can cause death.

The Ctenophores group have jellyfish, known as comb jellies. The shape of the body is like a ball, thimble or a belt. It has eight bands of comb-like organs on the sides of its body. They beat their combs in a co-ordinated way to move through the ocean. These jellyfish have sticky structures called colloblasts on their tentacles, to catch their prey. To transfer the food to its mouth, the comb jelly will spin around while contracting the muscles in its tentacles, so that they get wrapped in their own tentacles. This way the tentacles eventually sweep across the mouth and transfer the food.

All types of jellyfish have no brain to receive and interpret sensory information. The jellyfish depends on a network of nerve cells in their bodies, which are able to give them certain sensations and reactions. Certain types of jellies are able to react to light on the surface of the water and will move down to the ocean floor when the light starts to dim.
Normen FAdel
Author of the article
writer and blogger, founder of jellyfish .

New of label : Jellyfish Adaptations and Abilities

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