Carrie Yates, age 13, of Keen, N.H., for her question:
HOW DOES A SPONGE DEVELOP?
At one time it was thought that sponges were plants because they were attached to the bottoms of oceans and they did not move around. Now we know, of course, that sponges are water animals.
A sponge will start life as a single cell called an egg. This egg divides inside the body of the parent and keeps dividing until it forms a tiny larva or undeveloped animal form. It is covered with flagellated or runnerlike branches of cells.
When water circulates through the parent's body, it sweeps the larva outside the body. The tiny larva is then on its own. Its beating, lashing flagella move the larva through the water until it finally settles to the bottom of the ocean, where it attaches itself to a hard surface. The larva develops into an adult sponge there.
Sponges form an animal phylum called Porifera, which means pore bearers. The surface of the sponge's body is covered with lots of tiny pores.
Sponges can be found in all of the world's seas and in either shallow or deep water. More kinds and numbers of sponges live in the warm temperate and tropical waters than anywhere else.
Some sponges reproduce asexually, or without eggs. They do this by growing buds and branches that eventually break away from the parent sponge and grow into new sponges of their own.
Sponges have powers of regeneration, meaning they can regrow body parts. Even if much of the body breaks or is cut away, the sponge can replace the missing sections.
To test the regeneration powers of sponges, zoologists have pressed them through fine cloths so that all the cells of the sponge separate or divide into small groups. When the zoologists put the cells back into the water, the cells rearranged themselves to form a new sponge.
Many sponges come from Tarpon Springs off Florida's west coast and from the water off Key West, the Bahamas and Cuba. Lots also come from the Mediterranean Sea off the coasts of Egypt, Greece, Tunisia and Turkey.
Sponge fishermen in the deeper waters of the Mediterranean Sea and the Gulf of Mexico use diving suits to harvest their crops. In the shallow waters off the coast of Florida they use a hooking method that involves a glass bottom boat and a long pole with a pronged hook.
Sponges are spread out until the flesh decays. After all the decaying substances are removed, the fishermen hang the skeletons to dry.
Most of the so called sponges you buy in stores today are not true sponges. Instead, they are synthetic materials made to look and to absorb like true animal sponges.
True animal sponges, however, are definitely still available commercially today. These sponges can absorb large amounts of water and have qualities that make them excellent cleaning tools. Usually they are more expensive than man made sponges.