Category:Porifera

This article is about the aquatic animal. For the porous cleaning tool, see Sponge (material). For other uses, see Sponge (disambiguation).

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. Sponges do not have nervous, digestive or circulatory systems. Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes. Sponges were first to branch off the evolutionary tree from the common ancestor of all animals, making them the sister group of all other animals.

Sponges, the members of the phylum Porifera (/pəˈrɪfərə/; meaning "pore bearer"), are a basal Metazoa (animal) clade as a sister of the Diploblasts.[3][4][5][6][7] 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. The branch of zoology that studies sponges is known as spongiology.[8]

Etymology
The term sponge derives from the Ancient Greek word σπόγγος (spóngos).[9]

Overview
Sponges are similar to other animals in that they are multicellular, heterotrophic, lack cell walls and produce sperm cells. Unlike other animals, they lack true tissues[10] and organs.[11] Some of them are radially symmetrical, but most are asymmetrical. 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. Many sponges have internal skeletons of spongin and/or spicules (skeletal-like fragments) of calcium carbonate or silicon dioxide.[10] All sponges are sessile aquatic animals, meaning that they attach to an underwater surface and remain fixed in place (i.e., do not travel). Although there are freshwater species, the great majority are marine (salt-water) species, ranging in habitat from tidal zones to depths exceeding 8,800 m (5.5 mi).