Study questions for the Myxomycota, Dictyosteliomycota, and Plasmodiophoromycota

1. Cellular slime molds differ from true free living slime molds in several ways.
a. What is the assimilative phase for a cellular slime mold? What are the assimilative phases for a true slime mold?
b. Is the diploid phase of a cellular slime mold an important part of the life cycle? Why or why not? What about the diploid phase of the free living true slime molds?
c. Compare the roles of the plasmodial stage of true slime molds with the pseudoplasmodial stage of cellular slime molds in terms of asexual reproduction and dispersal.

2. What is the importance of aggregation in a cellular slime mold? What external condition triggers aggregation in Dictyostelium discoideum? What is the signal that myxamoebae release to promote aggregation?

3. At what stage do slime molds lack a cell wall? At what stage do they have cell walls?

4. Sporangia of the Myxomycota may have the following parts.

• a. Describe them and draw a sporophore with all the parts.

  hypothallus

  stalk

  peridium

  columella

  capillitium

b. What role is the capillitium thought to play in the life cycle of the Myxomycota?

5. What is the difference between a sporangium, an aethalium and a plasmodiocarp?
Draw the different structures.

6. Besides sporophore type, what are other characteristics used to distinguish between different orders of the Myxomycota?

7.Physarum polycephalum is heterothallic and has a bipolar mating system with multiple alleles at the mating type locus. What is the advantage of its having multiple alleles rather than the simpler 2 allele or +/- system?

8.Plasmodiophora brassicae is a member of the Plasmodiophoromycota.
a. What defines these organisms as different from the Myxomycota?
b. P. brassicae is sometimes grouped with the Oomycetes. This may be based on the part of the life cycle involving motile spores. How is this part of the life cycle similar to some of the Oomycetes like Saprolegnia?
c. The assimilative phase(s) and sexual reproductive phases of the P. brassicae life cycle, have similarities to the Myxomycota. What are the characteristics of these stages that support this argument. Your answer should include a discussion of nuclear content, and asexual and sexual reproduction.
d. What are the symptoms of the disease that P. brassicae causes in plants?

9. The Ceratiomyxales are unique among the Myxomycota in being exosporus. What does this mean?

10. Indicate the ploidy of the nuclei of the following cell types:

a. swarm cells

b. pseudoplasmodium

c. plasmodium of the Myxomycota

d. plasmodia of Plasmodiophora brassicae

18. Define:

endoparasite-

plasmagel-

grex-

sirenin-

zoospore-

gamete-

biflagellate-

gametangium-

myxamoeba-

plasmodium-

pseudoplasmodium-

sclerotia-