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The Eumycetozoa, or true slime molds, contain three groups of organisms:
the myxomycetes, dictyostelids, and protostelids. Respectively, as of 2006, these
have 888, 89, and 45 species known to science.
The myxomycetes (plasmodial slime molds) are a group of fungus-like
organisms usually present and sometimes abundant in terrestrial ecosystems.
The myxomycete life cycle involves two very different trophic (feeding)
stages, one consisting of uninucleate amoebae, with or without flagella,
and the other consisting of a distinctive multinucleate structure, the
plasmodium. Myxomycete plasmodia typically occur in cool, moist, shady
places such as within crevices of decaying wood, beneath the partially
decayed bark of logs and stumps, and in leaf litter on the forest floor.
Under favorable conditions, the plasmodium gives rise to one or more
fruiting bodies containing spores. The spores of myxomycetes are for most
species apparently wind-dispersed and complete the life cycle by
germinating to produce the uninucleate amoeboflagellate cells.
The fruiting bodies produced by myxomycetes are somewhat suggestive of
those produced by higher fungi, although they are considerably smaller
(usually no more than 1-2 mm tall). Although large enough to be seen with
the naked eye, they are best observed with a hand lens or under a
stereomicroscope. Only then can their intricate nature be fully
appreciated. Fruiting bodies may take the shape of tiny goblets, globes,
plumes, or other shapes more difficult to describe. Some occur in tightly
packed clusters, while others are scattered or even solitary. Many of the
more intricate forms have a spore case held aloft on a delicate stalk, but
others are attached directly to the substrate by their bases.
There are approximately 1000 recognized species of myxomycetes. The
majority of species are probably cosmopolitan, but a few species appear to
be confined to the tropics or subtropics and some others have been
collected only in temperate regions. Myxomycetes appear to be particularly
abundant in temperate forests, but at least some species apparently occur
in any terrestrial ecosystem with plants (and thus plant detritus) present.
Most of what is known about the assemblages of myxomycetes associated with
particular types of terrestrial ecosystems has been derived from studies
carried out in temperate regions of the northern hemisphere. In these
forests, myxomycetes are associated with a number of different
microhabitats. These include coarse woody debris on the forest floor, the
bark surface of living trees, and forest floor leaf litter. Each of these
microhabitats tends to be characterized by a distinct assemblage of
myxomycetes.
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Slime molds are a worldwide group. Please use the link to the
Global mapper
at the top of each individual species page to see its distribution.
You may also use this tool's "Make map" feature to build customized maps and
compare the distribution of different kinds of organisms.
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Great Smoky Mountains National Park
Prior to the beginning of the All Taxa Biodiversity Inventory of this park, 92 different species of
myxomycetes had been reported from the Park, and the majority of these
records were based upon specimens collected more than a half century ago.
In the past three years, more than 75 species have been added to this
total. The most surprising finds are four species of myxomycetes not
previously known from North America and two others that appear to be new to
science. However, it is anticipated that there are many more species to be
found. In fact, based upon the results obtained thus far, the Great Smoky
Mountains National Park appears to be one of the world's "hot spots" for
myxomycetes, with as many species present in the Park as anywhere else on
earth.
Visit the Tree Canopy Biodiversity page
for information on myxomycete diversity in the tree canopy of the Great Smoky Mountains National Park.
The myxomycetes are actually just one of three groups of organisms to
which the name "slime mold" has been applied, and the inventory currently
underway in the Park also includes these other slime molds--the
dictyostelids and protostelids. Members of both groups are so small that
they are virtually impossible to observe directly in the field. Instead,
surveys for dictyostelids and protostelids are carried out in the
laboratory by culturing these organisms from various types of organic
material brought in from the field.
Great Smoky Mountains National Park checklists and guide:
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