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Sponge? Sponges Scientific classification Kingdom: Animalia Phylum: Porifera Grant in Todd, 1836 Classes Calcarea Hexactinellida Demospongiae The sponges or poriferans (from the Greek poros "pore" and ferro "to bear") are animals of the phylum Porifera. They are primitive, sessile, mostly marine, water dwelling filter feeders that pump water through their bodies to filter out particles of food matter. Sponges are among the simplest of animals. With no true tissues (parazoa), they lack muscles, nerves, and internal organs. This means they are of cell grade construction, which is basically a lot of cells working together. Their similarity to colonial choanoflagellates shows the probable evolutionary jump from unicellular to multicellular organisms. There are over 5,000 modern species of sponges known, and they can be found attached to surfaces anywhere from the intertidal zone to as deep as 8,500 m (29,000 feet) or further. Though the fossil record of sponges dates back to the Precambrian era, new species are still commonly discovered. Sponges have several cell types: Choanocytes (also known as "collar cells"), flagellated cells which function as the sponge's digestive system, are remarkably similar to the protistan choanoflagellates. The collars are composed of microvilli and are used to filter particles out of the water. The beating of the choanocytes’ flagella creates the sponge’s water current. Porocytes are tubular cells that make up the pores into the sponge body through the mesohyl. Pinacocytes which form the pinacoderm, the outer epidermal layer of cells. This is the closest approach to true tissue in sponges. Myocytes are modified pinacocytes which control the size of the osculum and pore openings and thus the water flow. Archaeocytes (or amoebocytes) have many functions; they are totipotent cells which can transform into sclerocytes, spongocytes, or collencytes. They also have a role in nutrient transport and sexual reproduction. Sclerocytes secrete calcareous or siliceous spicules which reside in the mesohyl. Spongocytes secrete spongin, collagen-like fibers which make up the mesohyl. Collencytes secrete collagen. Spicules are stiffened rods or spikes made of calcium carbonate or silica which are used for structure and defense. Cells are arranged in a gelatinous non-cellular matrix called mesohyl. Sponges have three body types: asconoid, syconoid, and leuconoid. Asconoid sponges are tubular with a central shaft called the spongocoel. The beating of choanocyte flagella force water into the spongocoel through pores in the body wall. Choanocytes line the spongocoel and filter nutrients out of the water. Syconoid is a modification on this type with folds in the body wall and choanocytes lining canals within these folds. Leuconoid sponges lack a spongocoel and instead have flagellated chambers, containing choanocytes, which are led to and out of via canals. Sponges have no real circulatory system, however the water current is used for circulation. Dissolved gases are brought to cells and enter the cells via simple diffusion. Metabolic wastes are also transferred to the water through diffusion. Check out the following recipes that are tagged "Sponge":
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