Inorganic polyphosphates in the developing freshwater sponge Ephydatia muelleri: Effect of stress by polluted waters

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Abstract
Relatively high amounts of inorganic polyphosphates (approximately 55 μg of polyphosphate/g of wet weight) were found in the freshwater sponge Ephydatia muelleri, particularly in the gemmules (260 μg/g). Here we report that the polyphosphate content of this sponge changes during development and in response to adverse environmental conditions. Germination and hatching of gemmules of E. muelleri is accompanied by a strong decrease (by 94% at day 2) in polyphosphate level and a rise in exopolyphosphatase activity. On the other hand, induction of gemmulogenesis by theophylline results in an increase (by 61%) in polyphosphate content of sponge tissue. An increase in polyphosphate content and a decrease in exopolyphosphatase activity also occur during tissue regression when hatched sponges are exposed to polluted water from river. Nonionic organic compounds extracted from this water were identified as contaminants causing a rise in polyphosphate content of E. muelleri. The results show that measurement of polyphosphate level may be a promising method to detect responses of the freshwater sponge to polluted waters.