Aleta Slappoyo age 12, of Hawkinsville, Ga., for her question:
How is a sponge formed?
The bath sponge is a good subject for the game Animal, Mineral or Vegetable. Lets guess vegetable, for it looks like a dumpy little shrub. We'd be wrong. The sponge is not a plant, though 100 years ago many experts thought it was. Well, since it’s not alive, letts say mineral. This is partly right for it is made of minerals from the sea. Actually, the bath sponge is the skeleton of a water dwelling animal. It was formed as he grew.
Alive, the sponge looks even less like an animal. He has no legs, no head, no mouth, no lungs or gills, no heart, no nervous system and no feelings. And his strange skeleton is nowhere to be seen. He looks like a lump of dark slime. You can slice him in half without hurting him and the inside looks like ram liver.
The slimy rind of the sponge is a layer of tough, flattened cells. It is full of tiny pores through which mater enters the body, There is a deep tunnel which opens at the top of the sponge. A constant jet of water flows back into the ocean from this hole. The tunnel is lines with special cells called collar cells. Each has a tiny collar of jelly surrounding a little tail. Countless numbers of these tails constantly fan the water out of the tunnel.
The water brings oxygen and food to the sponge. It seeps in through the pores: in the skin and is circulated out again through the tunnel. Meantime, the cells of the sponge take out the oxygen they need and digest the bits of plant and animal debris.
The bulk of the sponge is between the rind and the central tunnel. This is made of wonderful little cells able to do almost anything. Th4y digest the foods use the oxygen, repair damage and any of them can become eggs. They also build the sketetan which becomes the bath sponge.
As the sponge grows big it needs some support. It needs to be held up in the water and the channels through which the water flows must be kept open. The inside cells extract minerals from the water and turn them into solid fragments. The bath spongets skeleton is a horny, elastic material called spongin. Other types of sponge make glassy skeletons from silica and still others make their skeletons of calcium carbonate.
Whatever the materials the skeleton is a lacy network of support for the soft cells of the sponge. The sponges that make skeletons of spongin live in warm ocean water. As babies, they may float or swim around for a few days, Then they settle on the sea bed and grew. A sponge may be big enough for market in three years. Then he may be plucked by a sponge diver.
The newly gathered sponges are left to dry and decay in the sun. Soon everthing but the skeleton can be washed away. The skeletons are beaten to break up any shells which may be hiding inside, then get their final rinsing. They are now ready to be baled and shipped off to do all kinds of cleaning jobs.