3. Baldauf and Doolittle, 1997. PNAS 94
(22): 12007-12012
Actin, elongation factor, and β-tubulin phylogenies place the plasmodial and
cellular slime molds as a monophyletic group close to Animal + FungI
4. Classification
Mycetozoa = cellular, plasmodial slime
molds plus protostelids
Cellular slime molds and protostelids now
placed in phylum Myxomycota
Names imply a fungal-like affinity
5. Myxomycota
Myxomycetes--5 orders, 13 families, 62
genera, 800 species
Characterized by plasmodium
Engulfs bacteria, fungal spores, small pieces
of organic matter
7. Stages in Life Cycle
Spores (2n n)
4-20 µm, pigmented
ornamented; meiosis
in spore = 4 nuclei; 3
degenerate
8. Stages in Life Cycle
Myxamoebae (n)
feed, divide, convert to
swarm cells, function
as gametes; form
microcysts under
adverse conditions
www.uoguelph.ca/~gbarron/ MISCE2002/myxamo2.jpg
9. Stages in Life Cycle
Swarm cells (n)
1-4 anterior whiplash
flagella, amoeboid
posterior; feed
(absorption and
engulfment), function
as gametes
can’t undergo cell
division
http://www.botany.hawaii.edu/faculty/wong/Bot201/Myxomycota/S
warm_Cells2.jpg
10. Stages in Life Cycle
Zygote (2n)
Formed by fusion of myxamoebae or swarm
cells; enlarges through synchronous nuclear
division
Plasmodium (2n)
Multinucleate, wall-less protoplasm
Photo by Stephen Sharnoff
http://www.plant.uga.edu/mycology-
herbarium/myxogal/Physros3.jpg
11. Stages in Life Cycle
Sporophore (2n)
Entire plasmodium is
converted into
sporophore(s)
Sclerotium or
macrocyst (2n)
Resistant stage
formed by plasmodium
12. Types of plasmodia
Phaneroplasmodium
Conspicuous, often colored, with protoplasm
forming veins with reversible streaming
Aphanoplasmodium
With a network of fine, transparent threads
and homogenous protoplasm
Protoplasmodium
Microscopic, with homogenous protoplasm,
giving rise to one sporophore
13. Sporophores
Mass of spores formed inside peridium, spores
intermingled with:
Capillitium
• threadlike, often ornamented
Elaters
• Threadlike, ornamented, not connected at ends
Pseudocapillitium
• Threads, bristles, membrane or platelike network
Lime may be present on peridium, stalk,
columella or capillitium, or nodes of
pseudocapillitum
14. Capillitium (top left; photo
by David Geiser)
Pseudocapillium (top right;
photo from Fifth Kingdom)
Elaters (bottom left)
www.botany.hawaii.edu/.../Bot201/ Myxomycota/elaters.jpg
26. Protostelids
Simplest known slime molds
Discovered in 1970
Easily mistaken for mucoraceous fungi or
deuteromycetes
In dead, attached plant parts, herbivore
dung or soil; feed on bacteria, yeast and
fungal spores
14 genera and 32 species
27. Protostelid Life Cycle
Amoeboid cells (filose pseudopodia)
become one or more prespore cells that
rise on stalk and encyst to form one to four
spores
Plasmodium and flagellated cells present
in “complex” life cycles
Sexual reproduction not known
28. Life cycle of simple protostelid
http://comp.uark.edu/~fspiegel/protist.html#sporocarp%20morphology
29. Life cycle of complex protostelid
http://comp.uark.edu/~fspiegel/protist.html#sporocarp%20morphology