Stephen Peters, age 14, of Long Boat Key, Fla., for his question:
WHAT IS A JELLYFISH?
A jellyfish will swim by expanding his body like an opening umbrella, and then pulling it together again rapidly. This motion produces an action that squeezes water out from beneath the body and the jellyfish moves upward. When these movements stop, the jellyfish slowly sinks to the bottom and on its way down it catches small animals for food.
A jellyfish is the common name for a type of sea animal that is also called a medusa. A jellyfish can range in size from one that is about seven feet in diameter to one that is no larger than a pea.
A jellylike material is found between the two layers of cells that make up the animal's body, and this is how he received his name. The sticky material acts as a skeleton to support the fragile body wall.
Looking something like an umbrella or a bell, the jellyfish has a short tube which hangs from the center of the body like a bell's clapper. The tube contains the animal's mouth.
The edges of the jellyfish's tube project into four frilly appendages called oral arms. Another group of projections, called tentacles, hang down from the edge of the body. Each kind of jellyfish has a certain number and length of tentacles.
The jellyfish is classified into the same group of animals that includes the corals, sea anemones and hydras. Large jellyfish make up a class that is called scyphozoan jellyfish. Often found along the coasts, scyphozoan jellyfish are sometimes called sea nettles. They are about the size of soup bowls and may be orange, pink, blue or other colors.
On the jellyfish's tentacles or oral arms are stinging cells that explode when touched by a victim, such as small animals on the ocean floor. The explosion drives tiny poisonous threads into the victim and paralyzes it. The victim is then passed to the mouth of the jellyfish and swallowed.
Some jellyfish can inflict painful and even dangerous stings to people.
Near the coasts of northern Australia and the Philippines is found a jellyfish called the sea wasp that has a poison deadlier than any snake venom.
Scyphozoan jellyfish produce their young from eggs. The eggs develop into small polyps which attach to the sea bottom. The jellyfish grow from the polyps by a process called budding. They are arranged on each polyp like a stack of saucers. The jellyfish, when they reach a certain size, are released from the polyp and they develop into adults.