We'll start by looking at the simplest of the intertidal animals, the sponges. The image above shows Leucosolenia spp. , commonly known as organ-pipe sponge. These sponges form colonies consisting of clusters or crusts of tubular, vase-like sponges.

Sponges, in general, feed by filtering tiny food particles from the current of water that they create around themselves. They use specialized cells that have paddle-like flagella, which look and function like large cilia. The water is drawn into the pores of the sponge by movement from the flagella and expelled through the osculum. Click on the image for a closer look.