Teaching with Zoosporic - Laboratory Exercise

                                        

Laboratory on Zoosporic Fungi 

The traditional three orders of the Chytridiomycota based on light-microscopy morphology are in bold. Dates on other orders and phyla are when the descriptions of these taxa were published.

 

Phylum Chytridiomycota

Class Chytridiomycetes

Order Chytridiales

Order Cladochytriales (2009)

Order Lobulomycetales (2009)

Order Rhizophlyctidales (2008)

Order Rhizophydiales (2007)

Order Spizellomycetales (1980)

Class Monoblepharidomycetes

                        Order Monoblepharidales

 

Phylum Neocallimastigomycota (2007)

                        Class Neocallimastigomycetes

                                    Order Neocallimastigales (1993)

 

Phylum Blastocladiomycota (2006)

                        Class Blastocladiomycetes

                                    Order Blastocladiales

 

Pure culture examination

For all chytrid cultures look at them first under the dissecting scope and choose an area with numerous thalli.  Take a very thin surface layer of agar with the thalli with a scalpel and make a wet mount.  Examine the cultures under LOW power first.  You will NOT need to go to oil to see most of these cultures. Diagram a thallus from each chytrid you look at and notice the type of thallus, if you see any asexual reproduction or sexual production. While looking at your slides and/or the cultures answer the following questions.

 

Gross culture examination

Look at the gross cultures of baited soil samples.  Examine some spruce pollen for chytrids and diagram their appearance.  Pollen should be colonized with chytrids.

 

1. Chytridiales

Chytriomyces- What is its thallus type? Are these chytrids undergoing asexual and/or sexual reproduction? Diagram and label how the process of plasmogamy occurs in this chytrid.

 

Rhizoclosmatium- What is its thallus type? Is it operculate or inoperculate? Do you see zoospores? Diagram and label a zoosporangium releasing zoospores.

 

Polychytrium- What is its thallus type? Is it monocentric or polycentric? What is the name of the hyphae-like structures of the thallus? Do you see zoospores? Diagram and label a portion of the thallus showing the morphological traits you answered.

 

2. Rhizophydiales

Rhizophydium- What is its thallus type? Is it operculate or inoperculate? Do you see zoospores?

 

Batrachochytrium- Examine the prepared slides of frog skin for thalli of this fungus. These are slides of a tadpole’s jaw sheath from Crocker Pond in western Maine. Diagram and label the thalli in the hexagon-shaped frog skin cells.

 

3. Spizellomycetales

Spizellomyces - What is its thallus type? Do you see rhizoids and/or zoospores? How do the zoospores and rhizoids differ from the Chytridiales? Diagram these differences.

 

Powellomyces- What is its thallus type? Is it exogenous or endogenous? How many rhizoidal axes do you see? Diagram and label the germling.

 

4. Monoblepharidales

Monoblepharis- Look at the demonstration of sexual reproduction.  Can you determine the two types of gametangia? Diagram and label these structures.  How does this reproduction differ from the Blastocladiomycota?

 

5. Blastocladiales

Allomyces - Make wet mounts of the sporothallic and gametothallic stages and diagram the stages.  Look at your handout on the life cycle and label your diagrams.  What are the advantages and disadvantages to this life cycle compared to those of the Chytridiomycota?

 

Typical Life Histories of Zoosporic Fungi   

   

Chytridiomycetes Life Cycle (Alexopoulos et al. 1996)

 

 

 

 

 

Monoblepharidomycetes Life Cycle (Alexopoulos et al. 1996)

 

 

 

 

Blastocladiomycota Life Cycle (Alexopoulos et al. 1996)

 

 

 

 

 

 

Current phylogenetic theory of “Chytrids” constructed by ribosomal DNA operon sequences. (adapted from James et al. 2006)

References

Alexopoulos, C.J., C.W. Mims, and M. Blackwell. l996. Introductory Mycology. 4th edition. Wiley, NY. 868 pgs.

James, T.Y., P.M. Letcher, J.E. Longcore, S.E. Mozley-Standridge, D. Porter, M.J. Powell, G.W. Griffith, and R. Vilgalys. 2006. A molecular phylogeny of the flagellated Fungi (Chytridiomycota) and description of a new phylum (Blastocladiomycota). Mycologia 98: 860-871.