The Mycetozoa or Myxomycetes comprise the true slime molds, peculiar protists which take the form of multinucleate amoeboids in the feeding stage but produce sporangia superficially similar to those of fungi. The spores release small haploid cells, which may take the form of flagellate swarmers or of small amoebae, which fuse together to form a diploid zygote. This grows to form the multinucleate plasmodium, as it is called, except in the Protosteliida where it remains uninucleate.
Plasmodia are found in moist terrestrial habitats. Many are brightly coloured, for instance white, brown, or yellow. Under dry conditions it may form a resistant structure called a sclerotium. A few slime molds get up to two square metres in size, the largest undivided masses of cytoplasm known. They are useful for studying cytoplasmic movements.
The slime molds were originally considered fungi, and treated under the botanical system of nomenclature as the division Myxomycota or class Myxomycetes (slime fungi). Zoologists treated the same organisms as the Mycetozoa (fungus animals). Both names are still used to refer to the group, but since they are not related to fungi and are related to other amoebae, the name Mycetozoa has gained some precedence. Sometimes the names Eumycetozoa, etc., are used to distinguish from cellular slime molds.\n