Micheal L. Deshazer, age 12, of Payette, Idaho, for the question:
How is a baby sponge born?
The parent sponge is a stodgy old stay‑at‑home. It cannot walk for it has no legs; It cannot swim for it has no fins, flippers or tentacles. It cannot see, smell or hear, for it has no senses. It cannot ioel pain, for it has no nervous system. It has not even any kind of brain. In all the animal kingdom, the sponge is most like a vegetable. In fact, many plants are more complex than a sponge,
Some 3,000 of these stodgy fellows have been named and classified. Almost all of teem live their lives squatting on the ocean floor. A very few, and all of them very small, live in fresh water. Many of these little fellows live their lives attached to floating logs.
A baby sponge may begin life as a bud from the body of its parent. All fresh water sponges begin life in this way and so do a few ocean sponges. Fresh water sponges living in temperate climates very often break apart in the cold weather. The soft tissue falls away leaving only the horny skeleton. When this happens, a wad of new cells is left wrapped in a skin. When conditions improve, a new sponge grows from this little seed package,
A budding sponge begins inside the body of the: parent. Special cells gather to help the bud get started. They leave when the little bud is able to take care of itself. Very often, a small fresh water sponge is made up from several generations of sponges that have budded from one parent body. Sponges that grow from buds never leave home.
Most sponges, however, begin life: with a few days of freedom. The parent sponge may produce both egg cells and fertilizing cells. Or the egg cells may come from one parent and the fertilizing cells from another. A baby sponge is on its way when an egg and a fertilizing cell meet and become one. Still sheltered inside the parent sponge, the fertilized egg divides into two cells, then in four, eight, sixteen and 32 cells.
The little embryo now begins to take on shape. It becomes an oval, flattened at one end. Some of the outer cells grow hair‑like mils called flagella. At last the baby sponge is ready to leave home, It leaves through one of the tunnels in the body of the parent sponge, waving its hair like flagella as it goes.
The baby sponge is a larva. For a few days he has the freedom of the seas. Life, however, is full of danger for he may get eaten by a hungry fish. He soon gives up this risky existence and sinks to the bottom. There he finds himself a solid rock, an empty sea shell or maybe: a colony of grown sponges. He firmly fixes himself and starts to grow. From here in ho will lead the stodgy stay‑at‑home life of his parents.