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Adaptive significance of polymorphic life cycles in protozoa: responses to starvation and refeeding in two species of marine ciliates
Fenchel, T. (1990). Adaptive significance of polymorphic life cycles in protozoa: responses to starvation and refeeding in two species of marine ciliates. J. Exp. Mar. Biol. Ecol. 136(3): 159-177
In: Journal of Experimental Marine Biology and Ecology. Elsevier: Amsterdam. ISSN 0022-0981, more
Peer reviewed article

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Keywords
    Adaptations; Biopolymorphism; Cysts; Ecophysiology; Encystment; Feeding; Starvation; Ciliata Couch, 1832 [WoRMS]; Pseudocohnilembus pusillus (Quennerstedt, 1869) Foissner & Wilbert, 1981 [WoRMS]; Uronema marinum Dujardin, 1841 [WoRMS]; Marine

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Abstract
    The life cycles of two related marine ciliates, Uronema marinum and Pseudocohnilembus pusillus were studied. Both species are adapted to exploit patches with high densities of bacteria such as decaying particulate matter. When growing cells of Uronema are deprived of food, the cells undergo from one to three cell divisions and form motile swarmer cells. These have a high motility and a long survival, but when refed they need a long lag time before they resume cell divisions. This reflects cell physiological change and reduction in metabolic rate during starvation and so the cost of long term survival. This ciliate is particularly adapted to exploit food resources with a patchy spatial distribution. Pseudocohnilembus cells do not divide when starved; instead they form motile swarmer cells and these can resume cell divisions quickly when food is available, but their survival time is only approximately equals 1/3 of that of Uronema cells. However, about half of the Pseudocohnilembus swarmers are capable of forming resting cysts 10-30 h after the onset of starvation.

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