Depending on the sponge, food is obtained through filtering water for nutrient-rich particles or snaring small sea creatures with specially adapted arms. Most sponges are detritivorous, consuming debris particles and microscopic life forms that float their way.
Living sponges are very similar to the cellulose sponges used for dish washing. Their open holes or pores, draw in water, filtering it for particle consumption. The water is then ejected from their bodies. The sponges eat using sticky, funnel-shaped collar cells that sway, drawing water through the cell. The collar cells also expel waste through a flagella, a long whip-like structure that holds the collar portion of the cell in place. The entire surface of the sponge can absorb food like this, making it a highly efficient feeder.
Scientists discovered the Harp sponge. Living at 11,000 feet under the sea, the Harp sponge was the first carnivorous sponge to be identified. They fish with arms known as vanes, which radiate out from their center. Each vane has vertical branches lined with hooks that snare tiny shrimp when the current brings them by. The sponge then envelops the shrimp in a membrane and digests it slowly.
There are two major divisions of sponge, encrusting, and free-standing. Encrusting sponges have amorphous, somewhat shapeless bodies. They cling to solid surfaces, such as rock, and grow in colonies, creating carpet like areas. Free-standing sponges have more distinct body shapes and come in a variety of forms. The largest free-standing sponge is the barrel sponge, which can stand taller than 6 feet. Because food rich waters are needed to allow sponges to grow to this size, larger sponges are found in deeper waters that are rich with life.