LYCOS RETRIEVER 
Sponges
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Sponges are primitive multicellular animals that live in water. All adult sponges are sessile (fixed to one spot), most being attached to hard surfaces such as rocks, corals, or shells. More than 4,500 living species are known. Although some species occur in freshwater, the vast majority are marine, living mainly in shallow tropical waters. Sponges have an amazing power of regeneration: they are capable of growing into a new individual from even the tiniest fragment of the original body.
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Sponges are filter feeders and extract both detritus and plankton from water currents that flow through them. In simple sponges, choanocytes, or collar cells, line the spongocoel- the internal cavity of a sponge. In more complex sponges, the choanocytes are confined to a system of branching cavities, called radial canals, created by the folding of the body wall. Each collar cell possesses a whiplike flagellum that beats and thereby produces water flow through the sponge. As this occurs, the cells engulf the food particles that adhere to their surfaces. After being engulfed by the collar cells, the food particles may be digested directly or transferred to another type of cell, termed an amoebocyte, for digestion.
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Sponges have the least complex body structure of all multi-celled creatures. A typical sponge is composed of an outer layer of tissue and a fibrous inner layer impregnated with numerous glass-like slivers of silica or calcium carbonate. The outer surface is riddled with small openings, joining a complex network of internal canals, through which water circulates. The inner canals are lined with special feeding cells, which are equipped with thread-like tails. Vigorous movements of these tails create a current that moves food-laden water through the sponge. A typical sponge pumps water equal to 5 times its own volume every minute.
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Sponges have no true circulatory system; instead, they create a water current which is used for circulation. Dissolved gases are brought to cells and enter the cells via simple diffusion. Metabolic wastes are ... transferred to the water through diffusion. Sponges pump remarkable amounts of water. Leuconia, for example, is a small leuconoid sponge about 10 cm tall and 1 cm in diameter. It is estimated that water enters through more than 80,000 incurrent canals at a speed of 6cm per minute.
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Sponges are made of four simple and independent cells. The first are the collar cells, which line the canals in the interior of the sponge. Flagella are attached to the ends of the cells and they help pump water through the sponge’s body. By pumping water, they help bring oxygen and nutrients to the sponge while ... removing waste and carbon dioxide. The second cells are the porocytes, which are cells that make up the pores of the sponge. Epidermal cells form the skin on the outside of the sponge.
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Sponges are not too sensitive to temperature, but do not like drastic shifts in salinity. Add a little bit of sea water (about 1/4 the original volume in the bag) of sea water to the bag containing the sponge every 10 minutes for about one hour. This will enable the sponge to slowly adjust the changing water conditions. Place your sponge in an area of the tank that has good water flow and minimum lighting. The flow will bring food to the sponge, and the diminished light will help to keep algae from over growing the sponge.
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Sponges