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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 509

Renate Meier, Werner Reisser, and Wolfgang Wiessner; [Cytological studies on the endosymbiotic unit of Paramecium bursaria Ehbg. and Chorella spec. II. The regulation of the endosymbiotic algal population as influenced by the nutritional condition of the symbiotic partners]. Arch.Protistenk 123:333-341, 1980

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The activity of acid phosphatase was analysed by histochemical methods in green and alga-free Paramecium bursaria with regard to its dependence on the nutritional conditions of the ciliate and to its significance for the regulation of the endosymbiotic algal population. In green Paramecia the activity of the acid phosphatase in food vacuoles increases after feeding with Enterobacter cloacae. The internal supply with carbohydrates by the symbiotic Chlorellae does not exclude the uptake of external food. The lack of an external food supply results in a low level of enzymatic activity in organisms cultured in both light and dark. A model is discussed referring to regulation of the endosymbiotic algal population. Its size is not regulated by digestion of the Chlorellae, but depends on the division rates of the symbiotic partners. In the dark, the division rate of algal cells is diminished due to the lack of photosynthetic activity, which cannot be compesated by a heterotrophic food supply. If the culture medium is devoid of suitable food, the number of algal cells soon decreases to reach a constant level, finally the whole symbiotic unit dies. Sufficient external food supply raises the division rate of the Paramecium to such an extent that the number of algal cells per Paramecium is statistically diminished resulting in alga-free Paramecia.