SPONGES: Porifera

PHYSICAL CHARACTERISTICS

Sponges are clumps of cells arranged around masses of tubes. The surface is covered with small holes. The movement of whiplike cells in the center of the sponge draws water through the holes and into the sponge. A pumping action moves the water through the sponge and out through a large hole at the end of each tube. The body of many sponges is supported by tiny rods or star-shaped structures called spicules (SPIH-kyoolz). In some sponges the spicules cover the outside of the body. In others they are interlocked to make a delicate framework. Sponges that do not have spicules are supported by strong, flexible fibers made of a protein called spongin. Some sponges have skeletons made of both spicules and spongin.

Sponges have a variety of shapes. Some form a crust on their rocky habitat. Some form a single straight tube. Others are vase shaped or cup shaped. Some sponges are massive clumps. Others are fan shaped. Some sponges have mitten-shaped or finger-like bulges on the body wall. Others are treelike or bushy. The height and width of sponges ranges from less than one inch (a few millimeters) to about 5 feet (1.5 meters). Sponges can be soft or hard, flexible or brittle. Some sponges are an almost colorless white or beige, and some are camouflage greenish brown. Some are brightly colored yellow or fluorescent reddish orange. Others are delicate shades of purple, lavender, light brown, or blue.

GEOGRAPHIC RANGE

Sponges live all over the world.

HABITAT

Most sponges live in the sea, but a few species live in freshwater. Many sponges live on reefs. Most sponges need a firm surface on which to attach, such as rocks or the skeletons of dead sponges and coral. Other sponges live on sand or mud at the bottom of the deep sea. Freshwater sponges live in lakes and streams.

DIET

Sponges eat tiny particles such as bacterial plankton that they filter from the water that flows through them. A few sponges, however, are carnivorous (kar-NIH-vuh-rus), or meat eating. They engulf and digest small crustaceans (krus-TAY-shuns), or water-dwelling animals that have jointed legs and a hard shell but no backbone.

BEHAVIOR AND REPRODUCTION

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.

IS BOB REALLY A SPONGE?

One of the most famous cartoon characters of the early twenty-first century is the square-pants-wearing SpongeBob, who looks like the brightly colored, rectangular objects many people use to clean their kitchen sinks. These cleaning tools, however, are not sponges. Most are made from cellulose, which is the main component of the cell walls of plants and also is used to make paper. Other kitchen "sponges" are made of plastic. The tan, irregularly shaped clumps that some people use for taking baths, for applying makeup, and for painting are the skeletons of dead sea sponges.

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.

SPONGES AND PEOPLE

Some sponges produce compounds that can be used to make drugs for fighting diseases caused by viruses and bacteria. Other sponges are harvested and sold as bath sponges.

DID YOU KNOW?

The volume of water passing through a sponge in one day can be as much as twenty thousand times the volume of the sponge.

CONSERVATION STATUS

Sponges are not threatened or endangered.

NO COMMON NAME (Soleneiscus radovani): SPECIES ACCOUNTS

Physical characteristics: Sponges of the species Soleneiscus radovani (abbreviated as S. radovani) are bushy looking and bright yellow. They have single, delicate tubes branching from a large tube in the center of the sponge. The outer tubes are about one-sixteenth of an inch (2 millimeters) in diameter. The entire sponge is less than 4 inches (10 centimeters) in diameter. S. radovani sponges are soft and delicate and easily torn.

Geographic range: S. radovani sponges live on the Great Barrier Reef, Australia.

Habitat: S. radovani sponges live in small patches of coral under overhangs.

Diet: S. radovani sponges are filter feeders that eat whatever is in the water that flows through them.

Behavior and reproduction: S. radovani sponges give birth to live young. Other than that, scientists do not know how these sponges behave or reproduce.

Soleneiscus radovani and people: S. radovani sponges have no known importance to people.

Conservation status: S. radovani sponges are not threatened or endangered. ∎

BIRD'S NEST SPONGE (Pheronema carpenteri): SPECIES ACCOUNTS

Physical characteristics: The shape of bird's nest sponges ranges from tall and narrow, like a barrel, to short and wide, like a cake. These sponges grow to a height of about 10 inches (25 centimeters) and a width of about 8 inches (20 centimeters). The thick, hollow body tapers to a single sharp-edged upper opening. Short thin, hairlike silica spicules surround the opening and stick out of the upper third of body. Longer spicules cover the lower third of the body and anchor the sponge in soft mud. The spicules on the middle third of the body are arranged in a pattern that looks like the interlocking twigs of a bird's nest. Bird's nest sponges are white.

Geographic range: Bird's nest sponges live in the northeastern part of the Atlantic Ocean from Iceland to northern Africa, including the Mediterranean Sea.

Habitat: Bird's nest sponges live on soft, muddy bottoms in the very deep ocean.

Diet: Bird's nest sponges are probably filter feeders.

Behavior and reproduction: Scientists do not know how bird's nest sponges behave or reproduce.

Bird's nest sponges and people: Scientists are trying to find out why there are so many bird's nest sponges in the deep ocean, where there are usually very few of any animal.

Conservation status: Bird's nest sponges are not threatened or endangered. ∎

FRESHWATER SPONGE (Spongilla lacustris): SPECIES ACCOUNTS

Physical characteristics: Freshwater sponges are crustlike, branched, or clumped. The texture is fragile and soft, and the color is whitish or green. Freshwater sponges have irregularly scattered and barely visible water-exit holes. The surface is uneven and roughened by spicules.

Geographic range: Freshwater sponges live in North America, Europe, and Asia.

Habitat: Freshwater sponges live in standing and running fresh water.

Diet: Freshwater sponges are filter feeders.

Behavior and reproduction: Scientists know little about how freshwater sponges behave. These sponges reproduce asexually by forming buds in late summer that spend the winter in a dormant state and emerge from the adult in the spring. Freshwater sponges reproduce sexually during the summer, giving birth to live larvae.

Freshwater sponges and people: Freshwater sponges have no known importance to people. Some scientists believe they may be helpful as indicators of water pollution.

Conservation status: Freshwater sponges are not threatened or endangered. ∎

FOR MORE INFORMATION

Books:

Aaseng, Nathan. Invertebrates. New York: Venture, 1993.

Carson, Rachel. The Edge of the Sea. 1955. Reprint, Boston: Mariner, 1998.

Layman, Dale. Biology Demystified. New York: McGraw-Hill, 2003.

Niesen, Thomas M. The Marine Biology Coloring Book. 2nd ed. New York: HarperResource, 2000.

Wells, Sue, and Nick Hanna. The Greenpeace Book of Coral Reefs. New York: Sterling, 1992.

Web sites:

Hartman, Holly. "The Science of SpongeBob." Pearson Education Fact Monster. http://www.factmonster.com/spot/spongebobscience.html (accessed on January 20, 2005).

Hill, Malcolm S., and April L. Hill. "Freshwater Sponges as Indicators of Water Pollution: An Investigative Undergraduate Lab." Labstracts.http://www.zoo.utoronto.ca/able/news/fall2000/page2-f00.htm (accessed on January 21, 2005).

"Porifera Questions." OceanLink: Ask a Scientist, Answer Archive. http://oceanlink.island.net/ask/porifera.html#anchor92351 (accessed on January 21, 2005).

"Sponges." Sponge Reef Project. http://www.pgc.nrcan.gc.ca/marine/sponge/index_e.htm (accessed on January 21, 2005).