Sponges …


  • are among the least complex members of the animal kingdom;
  • have no organs or tissues, though they do have many different kinds of cells;
  • have no distinct front, back, dorsal or ventral surface (though a few are radially symmetrical);Spong_guideIMG1
  • are built around a system of canals and chambers that allows them to filter large volumes of water;
  • have unique collar cells with a flagellum that drives water through the canals and chambers, and can move up to ten times the sponge’s body volume of water in an hour;
  • feed chiefly on particles the size of bacteria or smaller;
  • digest their food within cells, not inside a body cavity such as a stomach;
  • almost all produce a supportive mineral (silica or calcium carbonate) or organic (protein fiber) skeleton, or both;
  • are individuals, not colonies;Spong_guideIMG2
  • have separate sexes, or change sexes as they grow;
  • can reproduce asexually through buds or fragments that can give rise to another individual;
  • grow into a distinctive shape or vary widely depending upon factors such as currents, seafloor configuration or turbidity;
  • mostly live in the ocean (a few live in freshwater), attached to the seafloor for most of their lives (although their larvae can crawl or swim);
  • range in size from almost microscopic to over 3.5 meters across;
  • harbor diverse communities of bacteria with which they maintain unique relationships that may involve mediating bacterial metabolisms, and carrying out processes such as photosynthesis or nitrification;
  • probably number over 15,000 species (7,000 have been described scientifically);
  • often require microscopic examination of skeletal structures for identification.

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