Many sponges have internal skeletons of spicules (skeletal-like fragments of calcium carbonate or silicon dioxide), and/or spongin (a modified type of collagen protein). The shapes of their bodies are adapted for maximal efficiency of water flow through the central cavity, where the water deposits nutrients and then leaves through a hole called the osculum. Some of them are radially symmetrical, but most are asymmetrical. Unlike other animals, they lack true tissues and organs. Sponges are similar to other animals in that they are multicellular, heterotrophic, lack cell walls and produce sperm cells. Included are the yellow tube sponge, Aplysina fistularis, the purple vase sponge, Niphates digitalis, the red encrusting sponge, Spirastrella coccinea, and the gray rope sponge, Callyspongia sp.

Overview Sponge biodiversity and morphotypes at the lip of a wall site in 60 feet (20 m) of water. The term sponge derives from the Ancient Greek word σπόγγος ( spóngos 'sponge').

Sponges were possibly the first to branch off the evolutionary tree from the last common ancestor of all animals, which would make them the sister group of all other animals. Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes. Sponges do not have complex nervous, digestive or circulatory systems like humans. Sponges have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells. Sponges, the members of the phylum Porifera ( / p ə ˈ r ɪ f ər ə/ meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts.

Does young sponge move