Jennifer Pammer, age 10, of Allentown, Pa., for her questions
HOW DO THE LIVE SPONGES MULTIPLY?
Nowadays, most of our sponges are made of soft, porous plastic material. Before the age of man made plastics, sponges were the skeletons of strange sea dwelling animals. Like all animals, these live sponges multiply and produce offspring like themselves.
The average living sponge looks like a chubby little bush, sitting on the floor of the sea. He looks so much like a plant that it is hard to believe he really is an animal. Nevertheless he is, and when the time comes to multiply he has a problem. He is rooted to the spot, which means that he cannot go dating to find a mate.
However, in the case of the sponge, this is not necessary to produce a family. He is designed to act as mother and father. When it comes to reproduction, he has two choices. He may sprout small buds that later become new sponges. Sometimes the buds break away and start new lives of their own. Sometimes they remain attached to the parent sponge. What looks like a large sponge actually may be a parent and a dozen or so offspring produced by budding.
The second method of parenthood is more complicated and somewhat more risky. The adult sponge can produce eggs inside his porous body. At first the eggs measure about 1,000 to an inch. But they divide again and again, increasing the number of their cells. Finally they become small larva sponges, with hairy threads called flagella.
As water circulates through the porous parent, the little larvae are washed outside into the sea. There they wave their flagella to propel themselves through the water. For a time the small swimmers live a life of freedom. But the sea is a hungry place, and most of them are devoured by famished fishes.
At last the remaining young sponges sink to the
bottom. They anchor themselves to the floor and stay there, somewhat like rooted plants. The sea washes through their pores and tunnels, bringing them oxygen and scraps of floating food. For the rest ,of their lives they do not have to strive to make a living.
Adult sponges live a lazy, carefree life, for their spongy skeletons are too tough to be digested by hungry enemies. What's more, most fish dislike their odor and flavor. Most likely the young swimmers are eaten by accident, along with more tasty morsels.