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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 7741

Keith M. Jackson and Jacques Berger; Survivorship Curves of Ciliate Protozoa under Starvation Conditions and at Low Bacterial Levels. Protistologica XXI(1):17-24, 1985

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Survivorship curves of starved Condylostoma vorticella and Euplotes patella displayed a brief stationary phase, during which no deaths occurred, and a decline phase marked by an increasing mortality rate. Survivorship curves of Stentor coeruleus, Paraurostyla sp., Paramecium caudatum and Euplotes patella at low densities in low bacterial levels displayed a stationary phase followed by a decline phase which, in the cases of Paraurostyla sp. and E. patella, appeared to be marked by a constant mortality rate. The extended stationary and decline phases in these two cases were attributed to prolongation of ciliate survival resulting from ingestion of bacteria. During the decline phase, release of nutrients from lysed ciliates nourished bacteria and, hence, may have contributed to ciliate survival. Under such conditions, some cells survived, as a residual population, long after the beginning of the decline. Paraurostyla sp., P. caudatum, and E. patella at high population densities in low bacterial levels displayed survivorship curves that were similar in shape to those of starved species. Generally, survival was reduced for the species at high ciliate densities when compared to that at lower densities.