wpeE.jpg (7949 bytes)

Suspensor appendages of  Phycomyces

Almost all introductory courses in mycology cover Phycomyces.  It has several advantages as a teaching organism.

1.  It comes in plus and minus strains (see below for explanation) so you can inoculate a petri plate at opposite sides and the sexual structures are produced in a nice 'line' where the two strains meet at the centre (more or less) of the plate.

2.  It grows fast so that, under the right conditions, all of this happens in a week or so.

3.  The sexual structures are BIG!   At least big enough to see clearly under a dissecting scope.

4. It's easy to make good mounts for microscopy.

5.  You can actually photograph it on the petri plate with supermacro photography (whatever that is!).   Click here for a super macro shot of Phycomyces in a petri dish culture.

6.  The asexual sporangiophores are enormous (thicker than the hair on your head by far) and bend towards the light (positively phototropic).

7. On a single plate you can find gametangia,  progametangia, zygospores, suspensors and suspensor appendages.  Often, the suspensor appendages (black, branching, spiny outgrowths around the zygospore) arise from only one suspensor as in the case above.

Students: 

1. In Zygomycetes the hyphae are nonseptate but the left hand suspensor is clearly septate. Explain!

2. What is the diameter of a human hair? What is the diameter of a Phycomyces sporangiophore?

3.  How tall can a sporangiophore of Phycomyces grow?

PLUS AND MINUS STRAINS

In fungi the two sexes that mate are not morphologically different by distinctive sexual structures that allows us to identify them as male and female  i.e. the two strains that mate to produce the sexual spore (zygospore) look morphologically identical.   so as we cannot call them male or female strains, we designate them as plus or minus strains.  By convention the faster growing of the two strains is designated plus and the slower as minus.  And that can get you into an interesting box.