Sponges: Porifera

Most sponges attach themselves to the material on which they live. Some can penetrate deep inside rocks, coral, and shells. The main activity of sponges is pumping water through themselves to get food and oxygen, eliminate waste, and, for some sponges, process enough sand to make spicules. Sponges can control the amount of flow through their bodies by narrowing or partly closing off their intake and exit holes. Some sponges compete for space with corals and other sponges by releasing toxic chemicals.

Some sponges are either male or female, but others produce both eggs and sperm. Sponges use either sexual (SEK-shuh-wuhl) or asexual (ay-SEK-shuh-wuhl) reproduction. They are perhaps the most efficient animal at asexual reproduction, which happens without the uniting of egg and sperm or the transfer of DNA from two parents. Sponges can reproduce asexually when a piece of the adult's body breaks off and grows into a separate adult. In another method buds develop on the parent and then break off when they are large enough to live on their own.

Sexual reproduction is done by the uniting of egg and sperm and the transfer of DNA from two parents. Male sponges release sperm, which is taken inside females for fertilization (FUR-teh-lih-ZAY-shun), or the joining of egg and sperm. In some species of sponges the fertilized (FUR-teh-lyzed) eggs are released and then hatch outside the female's body. In most sponges, however, larvae (LAR-vee) develop inside the female's body and are born alive through the sponge's water-exit hole. Larvae are animals in an early stage that change form before becoming adults. Sponge larvae swim or crawl around for a few hours or days and then settle at the bottom of the water before transforming into adult sponges and attaching themselves to their permanent home.