Infection of Mayorella penardi (Gymnamoebia) in oak-hornbeam forest soil by the ectoparasitic fungus Amoebophilus simplex (Zygomycota)

During research on naked amoebae in terrestrial habitats in the oak-hornbeam forests of Malé Karpaty Mts. (Western Slovakia), a mass fungal infection in Mayorella penardi Page, 1972 (Euamoebida: Paramoebidae) was observed. In one of the 243 soil and moss samples examined a remarkably high percentage (80%) of amoebae were infected by the ectoparasitic soil fungus Amoebophilus simplex Barron, 1983 (Zygomycota: Zoopagales), as revealed by detailed light microscopical observations of infected specimens. The parasitic fungus displayed characteristic cylindrical conidia (length 10 μm, breadth 3 μm) projecting out from the posterior part of the amoeba cell. Infecting conidium frequently produced a chain of two to three conidia and, rarely, secondary chains from the distal end. Two to four infections in a single amoeba were frequently observed. From the present study, and from earlier records, it can be deduced that Amoebophilus simplex is specialized in parasitizing mayorellid amoebae, maybe even Mayorella penardi exclusively. Two other species (Korotnevella diskophora and Korotnevella stella) from the family Paramoebidae were recorded in the same sample, but neither of them showed signs of infection.