Janet Jones, age 9, of Nashville, Tennessee, for her question:
Do jellyfishes have bones?
When we think about life on other planets, we tend to imagine outlandish creatures, with bodies astonishingly different from our own. However, we do not have to visit other worlds to behold such wonders. Hundreds of the earth's very own creatures are astonishing. For example, chances are an imaginary Martian would be more like a man than a man is like a jellyfish.
Cats and dogs, horses and elephants and even tiny mice have bones in their bodies. So do many other favorite animals that share our world. Maybe we tend to think that bones are absolutely necessary to a body and that any animal would be lost without them. However, thousands of different animals manage very well without bones, thank you. There are almost half a million different insects and not a one of them has a bone inside its body. In the sea, there are many other boneless animals. For instance, you never find a bone inside the hard shell of a lobster or in the soft juicy body of a clam or an oyster.
The jellyfish is another boneless wonder, with bones neither inside nor outside and this fellow has at least 10,000 cousins. Some of them are little hydras that look like miniature tree trunks topped with twiggy branches. But their bodies are pliable gristle and they walk along by turning somersaults. The sea anemone squats his boneless body on the ocean floor and the boneless little corals build themselves rocky apartment houses. The various jellyfishes are swimmers and not one of them has a single bone.
As you would expect, a jellyfish looks somewhat like a blob of jelly. In most cases, he is a round fellow shaped either like a thick umbrella or an overgrown mushroom. His body is rather soft, but much tougher than that of an oyster and far more durable. Underneath his umbrella, a lot of thin tentacles stream down through the water. He swims along in jerks as he squeezes the edges of his umbrellas open and shut. Right in the middle of his round body is a round mouth that opens directly into his hollow tummy. He has special muscles that keep the water flowing back and forth through his mouth. And the water brings morsels of food for his tummy to digest,
Many jellyfishes are just a few inches wide. A rather flattish fellow, five inches wide, lives in the Atlantic Ocean. Around Greenland, his color is glassy white but farther south he wears blushing pink. A much smaller flattish fellow may glow in the dark.. The most common jellyfishes are eight or ten inches wide. They are blue white marked with circles of black or pink. In summer, swarms of them swim together just below the waves of the Atlantic and Pacific. The giant of the family is the sea blubber, alias the sun jelly. He is a glassy golden brown and sometimes his umbrella grows to be six or even seven feet wide. But he never grows bones.
Many jellyfishes have waspy stingers on their trailing tentacles. So beware. Even small fellows may cause a nettle rash just by touching your skin. Very often these boneless animals wash up on the beaches. Most of them soon dry up and wither away in the warm sun. But take care, their stingers go on working long after they are dead. The giant jellyfish is a deadly menance to ocean swimmers. His stinging tentacles can paralyze and even kill a human being.