Phosphatase activity of water-fleas, particularly on substances dissolved in surrounding water

Abstract

Alive water-fleas, maintained in a solution of sodium glycerophosphate (1 %) set free phosphate, in an average arnount of 0,015 gamma Ppc-r animal/hour Chydorus sphaericus, and of 0,(5 gamma P. per animal/hour Daphnia pulcx, at pH = 7,5-7,7 and t = 13-25° C. Presence of unicellular algae increases the enzymatic activity of cladocerans up to more than the donble (fig. 1). The water in which Daphnia has previously been living has a feeble phosphatasic activity, only 1/70- 1/100 of the total activity of alive crustaceans. This fact suggess that breakdown of glycerophosphate occurs chiefly in the gut of the ani­mal. However the required water circulation through the gut surpasses the known data about the renovation coefficient in Daphnia.

By trituration and autolysis of Daphnia pulcx, a fluid of phospha­ tasic activity has been obtained, with optimum pH point near 8,0 (fig. 2). At this point, activity amounts 8,4 unities (mg. of P set free in an hour, at 37° C, per g. wet weight). The phospliatases present in an adult Daphnia may 2,7 gamma of the 1’ in the separate conditions above stated
The importance of planktonic crustaceans in the cycle of phosphorns in natural waters is emphasized. They may be, indeed, able to modify the relations between the different P fractions (organic-inorganic) dissolved in lakes and seas.