Fungus

Any organism in the Kingdom Mychota. These organisms are incapable of photosynthesis, so they derive all their food from either dead or living plants and animals (i.e., they are saprophytes). Some fungal species are parasitic. Most are essential detritivores for the freestone rivers, and in terrestrial ecosystems, the rain forests. Many aquatic fungi or water molds (hyphomycetes) participate in the breakdown of leaf and other plant materials. They are essential, along with bacteria, for making the decaying vegetation palatable for the macro invertebrate shredder species.

Links
  http://www.mycolog.com/chapter11b.htm