2. INTRODUCTION
Myxomycetes, is a class of slime molds that contains 5 orders, 14
families, 62 genera and 888 species. They are colloquially known as the
plasmodial or a cellular slime moulds.
3. MYXOMYCETES
It is a group of organisms of great scientific interest. Some of these are
of remarkable beauty, have delicate structure and brilliant colours.
They exist in non-green slimy masses of protoplasm sending out
pseudopodia. This has earned for them the name slime molds or slime
fungi.
They are found in cold, moist shady places in dead organic matter
such as decaying logs and fallen dead leaves in the woods. The class
includes the true plasmodial acellular slime molds most of which
produce pigmented spores in small, delicate sporangia.
4.
5. CHARACTERISTICS OF MYXOMYCETES
The somatic phase is represented by a multinucleate apparently
naked acellular slimy protoplasmic mass called the Plasmodium.
The Plasmodium is the product of syngamy, hence a diploid structure.
The diploid Plasmodium is holocarpic, free living and active. It
contains and secretes slime.
Normally at the fruiting time, the entire Plasmodium is organised into
one or more plantlike reproductive structures, the sporangia
(sporophores) or under conditions of stress and strains it becomes
converted into an irregular hard structure, the sclerotium.
6. CLASSIFICATION OF THE MYXOMYCETES
(i) Ceratiomyxomycetidae:
It contains a single order Ceratiomyxales represented by a single family
Ceratiomyxaceae. Ceratiomyxa with three exosporous species is the only genus
included in this family.
(ii) Stemonitomycetidae:
It includes a single order Stemonitales which comprises only one family
Stemonitaceae. It is endosporous. The somatic phase is of aphano-plasmodium type.
(iii) Myxogastromycetidae:
It comprises four orders namely Physarales, Siceales, Echinosteliales and Trichiales.
All are endosporous. The somatic phase is usually of protoplasmodial or
phaneroplasmodial type. The class Myxomycetes thus contains six orders. Of these
Physarales belonging to the subclass Myxogastromycetidae is the most important.
7. FEATURES OF MYXOMYCETES
The Myxomycota or slime molds, are fungus-like organisms. They are
characterised by the absence of cell wall from their amoeboid,’ animal-like
vegetative or assimilatory phase.
The amoeboid assimilatory phase may consist of a free-living multinucleate
mass of protoplasm called a plasmodium or simple uninucleate amoeboid
cells, the myxamoebae.
Plasmodial slime molds are the true slime molds, pseudoplasmodial slime
molds the cellular slime molds and the net plasmodial slime molds are
known as the net slime molds.
The true slime molds are mostly saprophytic with a few parasitic ones.
The spores escape as biflagellate zoospores which after swimming for some
time, lose their flagella become surrounded by delicate envelope and give
rise to new net plasmodium.
8. REPRODUCTIVE PHASE OF MYXOMYCETES:
Normally on reaching a certain stage of maturity, the Myxomycete
Plasmodium passes into the reproductive stage. During this stage the
entire Plasmodium becomes converted into one or more fruit-like
bodies, the sporophores or spororigia which bear the spores. This
process is termed sporulation.
With the exception of three species belonging to the order
Ceratiomyxales which bear spores externally and are termed
exosporous, all other Myxomycetes are endosporous. The latter bear
spores within sporophores. The sporophores in the endosporous
Myxomycetes chiefly are of three types namely sporangia, aethalia and
plasmodiocarps.
9. Sporangia:
Most of the endosporous Myxomycetes (order Physarales) produce fruit
bodies of this type. At the fruiting time the planeroplasmodium becomes
converted into a group of several stalked, sometimes sessile sac-like
structures, the sporangia. The sporangia in the group remain separate
from one another.
Aethalia:
Aethalium type of fruit body is characteristic of Lycogala and Fuligo. The
Plasmodium, at the fruiting time is fairly large structure. It becomes
converted into a group of saclike sporangia that do not separate from one
another.
10. Plasmodiocarp:
In forms like Hemitrichia the fruit body is very much like a sessile
sporangium that retains the shape of the plasmodial venation. This type of
sporophore is called a plasmodiocarp. It is formed by the concentration of
the plasmodial protoplasm around some of the main veins followed by the
development of peridium around each
