1. What is the difference between the way that a plasmodium of the slime molds and a pseudoplasmodium of the cellular slime molds are formed? How do they differ in terms of their chromosome content (haploid? dikaryotic? diploid?)? (3 points)
A plasmodium grows from a diploid zygote into a multinucleate mass. The nuclei within the plasmodium are diploid and replicate by mitosis as the organism grows.
A pseudoplasmodium is a multicellular structure that forms by aggregation of many single haploid amoeboid cells. These cells remain haploid and do not replicate in the pseudoplasmodium.
2. Hyphochytriomycota are said to be either holocarpic, or eucarpic. What do these terms mean? Rhizidiomyces apophysatus is an example of a eucarpic member of this phylum. Explain why, based on what you know about the structure of this fungus. (2 points)
Holocarpic - The whole thallus is converted into reproductive structures.
Eucarpic - Reproductive structures are formed on only a portion of the thallus.
R .apophysatus is eucarpic, because the sporangium forms from only a portion of the thallus. The rhizoids and apophysis remain within the host.
3. What are the two structures called in the figures? How do you know which is from Saprolegnia and which is from Pythium? How do these structures differ in terms of release of their contents? (3 points)
The two structures (see your quiz) are the sporangia of Saprolegnia (upper diagram) and of Pythium (lower diagram). The structures are recognizable by their shapes, with the sporangium of Saprolegnia being elongate and slightly wider than the hyphae, while the sporangium of Pythium is rounded. The zoospores are released directly from the Saprolegnia sporangium, while for Pythium, the protoplasm of the sporangium moves into a newly-formed vesicle and then is differentiated into zoospores.
4. Label the oogonia, antheridia and oospheres in the figures below. Which of these structures are the gametangia? How do you know which is from Saprolegnia and which is from Pythium? (3 points)
The oogonia and antheridia are the gametangia. In Saprolegnia, there are multiple oospheres per oogonium, while in Pythium there is only a single oosphere per oogonium.