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The Collaborative International Dictionary
slime mold

slime mold \slime mold\, slime mould \slime mould\n.

  1. An unusual fungus-like protist of the phylum Myxomycota or the class Myxomycetes, having a stage of growth in which it comprises a naked noncellular multinucleate mass of creeping protoplasm having characteristics of both plants and animals; it also has a propagative phase in which it develops fruiting bodies bearing spores; it is sometimes classified as a protist. It is called also acellular slime mold. [WordNet 1.5 +PJC]

  2. Any of several remarkable amoebalike organisms of the phylum Acrasiomycota, mostly terrestrial, having a fruiting phase resembling that of the acellular slime molds, but being cellular and nucleate throughout their life cycle; called also cellular slime mold. The most studied species is Dictyostelium discoideum. In their feeding phase, they live like amoebae as individual cells, engulfing bacteria as a prime food source. When the food source diminishes, they begin to aggregate, swarming together to form clumps which may move toward heat and light, so as to reach the surface of the ground; they then differentiate into a form with spores contained within a sporangium resting on a stalk. When the spores are carried to another location with adequate food supplies, the spores may germinate to resume the life cycle. The phase of aggregation appears to be initiated by release of cyclic AMP, serving as a signal between the individual cells. The formation of the fruiting body has some similarities to differentiation in multicellular organisms, but the mechanisms are still under study. Some biologists object to the classification of Dictyostelium as a slime mold, as it is neither a mold nor slimy.

Wiktionary
slime mold

n. Any of various primitive organisms, a naked mass or protoplasm, of the phylum ''(taxlink Acrasiomycota phylum)''

WordNet
slime mold

n. a naked mass of protoplasm having characteristics of both plants and animals; sometimes classified as protoctists [syn: slime mould]

Wikipedia
Slime mold

Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms that can live freely as single cells, but aggregate together to form multicellular reproductive structures. Slime molds were formerly classified as fungi but are no longer considered part of that kingdom. Although not related to one another, they are still sometimes grouped for convenience within the paraphyletic group referred to as kingdom Protista.

More than 900 species of slime mold occur all over the world. Their common name refers to part of some of these organisms' life cycles where they can appear as gelatinous "slime". This is mostly seen with the myxogastria, which are the only macroscopic slime molds. Most slime molds are smaller than a few centimeters, but some species may reach sizes of up to several square meters and masses of up to 30 grams.

Many slime molds, mainly the "cellular" slime molds, do not spend most of their time in this state. As long as food is abundant, these slime molds exist as single-celled organisms. When food is in short supply, many of these single-celled organisms will congregate and start moving as a single body. In this state they are sensitive to airborne chemicals and can detect food sources. They can readily change the shape and function of parts and may form stalks that produce fruiting bodies, releasing countless spores, light enough to be carried on the wind or hitch a ride on passing animals.

They feed on microorganisms that live in any type of dead plant material. They contribute to the decomposition of dead vegetation, and feed on bacteria, yeasts, and fungi. For this reason, slime molds are usually found in soil, lawns, and on the forest floor, commonly on deciduous logs. However, in tropical areas they are also common on inflorescences, fruits and in aerial situations (e.g., in the canopy of trees). In urban areas, they are found on mulch or even in the leaf mold in gutters, and also grow in air conditioners, especially when the drain is blocked. One of the most commonly encountered slime molds is the yellow Physarum polycephalum, found both in nature in forests in temperate zones, as well as in classrooms and laboratories.