Ecology of Heterotrophic Microflagellates. III. Adaptations to Heterogeneous Environments

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Abstract
The response to starvation and to feeding after a period of starvation was studied in heterotrophic microflagellates. Starvation immediately leads to a decrease in metabolic rate which eventually falls to 2-5% of that characteristic for growing cells and to autophagy of cell organelles, in particular mitochondria. At the onset of starvation, the studied species undergo one or 2 additional divisions leading to small, more lively cells. When starving cells are fed, they immediately take up food and increase their O2-uptake; the time lag after which cell division and a metabolic rate characteristic of growth occur increases with starvation time. These properties are discussed in terms of adaptation to temporally heterogeneous environments, and the behavior found must be a compromise between the ability to survive and to resume cell divisions rapidly when food is again available. The absence of cysts in the studied forms is discussed; the techniques employed for obtaining clonal cultures select against cyst-forming species or clonal lines.