1. Plasmodial Slime
Molds

2. http://www.ucmp.berkeley.edu/chromista/chromistasy.html
Ribosomal RNA phylogenies place slime molds as unrelated, early
branching eurkaryote lineages

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

6. Physarum life cycle
meiosis
microcyst karyogamy
Synchronous mitotic divisions
macrocyst

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

15. Sporocarp—stalked or sessile
May have columella 

16. Aethalium
 Large, cushion-shaped
sporophore, one per
plasmodium

17. Pseudoaethalium
 Cluster of sporophores
grouped tightly
together
Photo by David Geiser

18. Plasmodiocarp
 Sporophore developing
along veins of
phaneroplasmodium;
takes on reticulate
shape of veins

19. Photo by Stephen Sharnoff

20. Liceales-- Pale or brown spores, capillitium and lime absent,
pseudocapillitium may be present
Dictydium
Lycogala Photo by Stephen Sharnoff

21. Trichiales--Pale spores (yellow, orange or red) and abundant,
conspicuous capillitium
Trichia
Arcyria

22. Physarales--Purplish-brown spores, usually with abundant
and conspicuous lime on or in sporophore
Badhamia
Leocarpus Fuligo

23. Stemonitales--Violet-brown spores, lime absent
Lamproderma
Diachea

24. Photo by Stephen Sharnoff
Stemonitis

25. Ceratiomyxales--Exosporous sporophores; probably
belongs in protostelids (one genus, Ceratiomyxa)
Photo by Stephen Sharnoff Photo by David Geiser

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

30. Images courtesy of Fred Spiegal, Univ. of Arkansas