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.
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?
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.