Porifera are some of the simpliest animals. They are multicellular, yet they have no tissues or organs. They cannot move, and they eat by filtering sea water. Sponges of the family Cladorhizidae are especially unusual in that they typically feed by capturing and digesting whole animals. They capture small crustaceans with their spicules which act like Velcro when they come in contact with the crustacean exoskeletons.
Cells then migrate around the helpless prey and digestion takes place extracellularly.
A sponge has no definate shape, but is usually a long cylindar, hollow in the middle, with pores. These pores act as funnels to let food and water in, but only water out. A sponge eats by sucking and filtering water to catch microscopic organisms for food.