Field and Laboratory Studies of Encysted and Trophic Stages of Naked Amoebae: Including a Perspective on Population Life Cycle Dynamics

O. Roger Anderson


Naked amoebae are among the most abundant soil protists, especially in highly productive soils. Their capacity to produce cysts during unfavorable growth periods, especially drying, enhances their survivability as resting stages and promotes dispersal by wind and air currents. However, the dynamics of their cycles of encystment and active growth are poorly documented. Using a recently developed culture observation method, including a dried preparation stage to detect encysted amoebae, data are presented on the ratios of active and encysted stages of naked amoebae based on field samples from diverse terrestrial sites differing in plant cover and moisture content during spring and summer months 2008 at a location in northeastern U.S.A. Percentage of encysted amoebae varied between 32% and 100% depending on locale and moisture content. Carbon content of the cysts (estimated from recently excysted individuals) relative to trophic stages varied between 22% and 100% at these same locales. Laboratory experimental studies of winter soil samples, that were cultured at 25oC to promote amoeba community growth, indicated that a dynamic relationship exists between active and encysted stages during proliferation with varying ratios depending on the moisture content and qualities of the soil at the collection site, thus suggesting a revised model as presented here of the encystment-excystment cycle for populations during a growth succession.

Słowa kluczowe: Eukaryotic microbial communities, microbial ecology, microbial survival strategies, protistan community succession

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