Includes sponges Interesting facts: - Sponges are filter feeders, which is when water is absorbed through the pores and filtered by cells called choanocytes. - They do not have true skeletons, only small structures called spicules made of calcium carbonate . - These animals were widely used as kitchen sponges until synthetic sponges were invented., Sponge on field guide: Turkey Cup Sponge (Spongia officinalis)