JellyFish Facts

Jellyfish Bodies

Jellyfish Bodies picture

Jellyfish Bodies

Jellyfish are perhaps the most fascinating creatures of the marine kingdom. While they may look shapeless and colorless when they get washed up on the shore or caught in fishing nets, they look hypnotically beautiful when they are floating in water. Found practically in all marine waters of the world, the jellyfish is perhaps the oldest living creature in the world, having survived for more than 650 million years. The body of the jellyfish also makes for a very interesting study.

The body of the jellyfish mainly consists of a bell which confirms to radial symmetry. It radiates from the central axis and is perfectly symmetrical from all sides. This perfect symmetry is very useful for the survival of the jellyfish because it allows jellyfish to detect food as well as protect itself from predators from all sides.

The bell of the jellyfish consists of an outer layer called the epidermis and an inner layer called the gastrodermis. The epidermis contains of nerve receptors that can detect light, odor, pressure and other stimuli. The interesting thing about the nerve receptors in the epidermis is that they are not controlled by any brain. In the bell of the jellyfish, there is only a central nervous system and the nerve receptors themselves are capable of devising a reaction to any external stimuli they encounter. The inner layer of the bell or the gastrodermis lines the gut of the jellyfish. The space between the epidermis and the gastrodermis and filled with gelatinous, elastic like matter, called mesoglea. In the bell of the jellyfish, there exists a small digestive cavity which contains the gullet, stomach and intestines. The cavity begins at the mouth of the jellyfish and ends at the anus.

There are usually four to eight oral arms that protrude from the edges of the bell of the jellyfish. The main purpose of these oral arms is to help transport food to the mouth of the jellyfish. Many species of jellyfish also have clusters of tentacles emerging from under the edges of the bell. These tentacles have thousands of venom filled nematocysts on them and are mainly used to sting the prey and paralyze it. These tentacles are also useful to sting a likely predator and protect the jellyfish.

The jellyfish is not capable of any horizontal movement. For that, it depends upon the tides of the water and the winds at the surface of the water. However, the bell of the jellyfish enables it to control its vertical movements. By pumping water in and out of the bell, the jellyfish is able to thrust itself upwards or downwards in the water.

The size of the bell of the jellyfish varies from species to species. It can range from a few centimeters to a few feet in diameter. The largest known jellyfish had a bell that measured 7 feet in diameter. The color and patterns of the bell of the jellyfish also differ from one species to another and can encompass a very wide range in shades and designs.

Learn more about Jellyfish, different Jellyfish Species, general Jellyfish Information, Jellyfish Pets and Jellyfish Safety

Written by and Sudarsana Sinha.

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