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.