In the simple plan, the interior water space, or atrium, is large and unpartitioned. These plans are not directly related to taxonomic groups. Sponges have three levels of organization: simple, compound, and complex (called asconoid, syconoid, and leuconoid in your textbook – but you don’t need to know these terms) that reflect the complexity of the sponge’s body plan. The flow of water through sponges affects sponge feeding, reproduction, and gas exchange. The body of the sponge encloses internal water spaces that are continuous with the surrounding environment through incurrent ostia and excurrent oscula. The mesohyl includes the secreted skeleton: protein fibers of collagen (= spongin) and/or mineral spicules of calcium carbonate or silica. The choanoderm is composed of flagellated collar cells, or choanocytes. Most of the sponge body is a connective tissue, the mesohyl, with internal and external layers of cells, the outer pinacoderm and the inner choanoderm. Individual cells keep their mobility and totipotent ability (they can become other types of cells). Sponges are organized collections of relatively independent cells. They are efficient filter feeders specializing on bacteria-sized particles. Modified, with permission, from Invertebrate Anatomy OnLineĬopyright 2003 by Richard Fox (Lander University)Īlthough sponges can be found in freshwater, they are much more common and diverse in marine habitats, where they are often important members of benthic communities.
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