Though plant-like in appearance, sponges are actually one of the most primitive animals in the sea. They belong to a group called porifera. Most of us are familiar with the dried colorless varieties that populate the kitchens and bathrooms of the world. Only about seventeen are of commercial value. Sponges are the most primitive of the multicellular animals, containing neither true tissues nor organs.
Sponges spend most of their time filtering and cleaning sea water.
They are constantly sucking in water through small pores on their sides and shooting it back out through the ostium, or opening, located at the top of their bodies. A Household Word Sponges are one of the simplest of animals on the planet. They consist of collections of similar cells held together by prickly, needle-like spicula. From the looks of them, giant red sponges do little more than wave gently back and forth in the warm Caribbean current. Actually, they are busy feeding on thousands of microscopic pieces of plants and animals.