WAR of the MICROWORLDS
How do I kill Thee? Let me count the Ways! (# 33) click here for full list
(Images from Mycoalbum CD)
Conocybe albipes (Dunce Cap). This species, formerly known in North America as Conocybe lactea, produces remarkably well developed secretory 'cells' on the vegetative hyphae. The toxin produced by these cells kills nematodes, BUT, unlike other 'mushroom' predators such as Pleurotus and Hohenbuehelia, the dead and dying victims are NEVER invaded by the fungus as a nutrient source (note: never say never in biology). It appears that the secretory appendages function as deterrant devices (antifeedents) that protect the fungus hyphae from attack by nematodes and perhaps other microfauna that would use them as a food source. It is tempting to suggest that predation of nematodes by Basidiomycota such as Pleurotus and Hohenbuehelia began, in this way, with the production of protective antifeedents. BASIDIOMYCOTA. For further information on this association see Hutchison, L.H. , S. E. Mazdia and G. L.Barron. 1996. Can. J. Bot. 74: 431-434.
Right Micrograph: The toxin droplets on the right hand side of the field have been swept away (droplets have disappeared) by the 'swimming' action of the nematode. The nematode has now succumbed to the effects of the toxin produced by the secretory cells as droplets. The dead nematode will lie around for many days but, unlike Pleurotus, there is no attempt on the part of the Conocybe to produce directional hyphae that will invade and exploit the victim as a nutrient source. There is good reason to suppose that the toxin droplets will be equally effective as antifeedents against other potential microfaunal predators of the Conocybe hyphae e.g. mites springtails etc. This hypothesis would be easy enough to test and I found it to be true for Pleurotus ostreatus.!
It is also interesting to consider the efficacy of toxic droplets as weapons of attack/defence compared to host specific methods such as sticky nets and knobs etc that confine their attacks to nematodes and noot all species of nematodes are affected. Toxins could be equally effective against a wide range of microfauna i.e. biocides rather than merely nematocides.
Regarding the relationships of this species, there are a number of morphotypes of Conocybe lactea (sensu lato) that along with Gastrocybe lateritia require closer attention!