The body of the jellyfish

Skeletal system and brain is absent in jellyfish. Instead, it has a network of nerves called nerve net, which is capable of sensing odor, light and other similar stimulations. This simple yet effective nervous system helps the jellyfish to respond with lightning speed.

Jellyfish has two layers of skin - epidermis or the outer layer and gastrodermis or the gut lining. A layer of thick gelatinous substance called mesoglea fills the portion between these two skin layers. This gives jellyfish its name and the translucent appearance.

The main body of a jellyfish is bell-shaped with tentacles extending from underneath the body. Different species vary vastly in size, color and shape. The smallest measures barely an inch in diameter, while the largest can measure up to seven feet across the bell. The tentacles also are proportional with some extending more than 100 feet.

The body of the jellyfish consists of more than 95% of water and less than 5% of organic matter. Due to this, jellyfish are extremely delicate and fragile and when removed from water, they will collapse completely.

The mouth of the jellyfish is located at its underside. A gastro vascular cavity adjoining the oral opening serves as the stomach. The food entering the mouth is immediately digested in this chamber and the nutrients absorbed into the body. The nutrients reach all parts of the body through radial canals. The waste matter generated during digestion is expelled through the same opening.

As jellyfish doesn't have teeth or any other mechanism for chewing the prey, the food is swallowed and digested without breaking it down. The gastrodermis helps in digesting the food.

Personally, the most remarkable thing i feel about a jellyfish is that it can survive without possessing a heart, brain, respiratory system, skeletal system, central nervous system or blood. This is because all multi cellular organisms need these to survive but the jellyfish does not. Due to its thin skin, i think the jellyfish is also the only multi cellular organism that takes in oxygen through diffusion.