WAR  of  the  MICROWORLDS  

How do I kill Thee?   Let me count the Ways!   (# 3)

Meria harposporioidesThe spore (conidium) of the parasitic fungus is drawn to the protozoan host by the current generated by its cilia.   The conidium attaches and bonds to the outside of the protozoan pellicle (wall) probably by a lectin/carbohydrate recognition system.   The spore then germinates and penetrates  into the interior of the host by means of a long, narrow, penetration tube.   After the contents of the host are digested, the branching fertile hyphae of the fungus break out to the exterior of the animal and produce more conidia (see below). DEUTEROMYCOTAFor further information on this species see Barron, G.L. and Szijarto, E. 1982. A new hyphomycete parasitic on the ciliated protozoans Opercularia and Vorticella. Can. J. Bot. 60: 1031-1034.

wpe209.jpg (33596 bytes)     wpe207.jpg (32958 bytes)  

    Left: Meria harposporioides Attacking Ciliated Protozoan Opercularia.     Right: Healthy Protozoan

Right hand image shows healthy protozoans with apical cilia.

Left hand images shows an early infection stage inside the parasitized protozoan.  The fungus spore (conidium) is drawn into the protozoan by the action of the current created by the cilia drawing in water to garner food particles.    The fungus attaches to the outside wall of the host, penetrates and forms a narrow infection tube.  The tube expands at the tip to form broad, branching assimilative (feeding) hyphae that absorb the contents of the protozoan.   This species is obviously not in the genus Meria so anyone interested can transfer it somewhere else but to get it right they may have to find it first and then do a molecular analysis!

BELOW:  Mature infection producing ferile hyphae, conidiogenous cells, and conidia outside the parasitized host

wpeF.jpg (54564 bytes)

The fertile hyphae of the parasite have grown out through the pellicle of the ciliated protozoan host and are starting to produce conidia from tiny 'phialidic mouths' arising laterally from the fertile hyphae.    You can appreciate that the natural relationship of this fungus is not clear but it shows vague affinities to Drechmeria, Harposporium, Verticillium and Rotiferophthora???   This is where molecular studies will help significantly to clarify the true position in the scheme of things of ALL of these and related parasites of microscopic animals.