THE PHYSIOLOGY OF DIGESTION IN PLANKTON CRUSTACEA

II. FURTHER STUDIES ON THE DIGESTIVE ENZYMES OF (A) DAPHNIA AND POLYPHEMUS; (B) DIAPTOMUS AND CALANUS

¹ From the Limnological and Physiological Chemistry Laboratories of the University of Wisconsin

1. Three peptidases (dipeptidase, aminopolypeptidase and carboxypolypeptidase) were found in water extracts of Daphnia. The presence of these and a proteinase (author, 1935) demonstrate that Daphnia can completely utilize a protein.

2. Proteinases of Daphnia were no more active than those of the hog pancreas at a temperature of 8° C. Both enzyme systems follow, in general, the van't Hoff rule.

3. Proteinases, amylases and lipases were found in glycerol extracts of Polyphemus and Diaptomus. All proteinases were of the tryptic type with an optimum activity at pH 7-8. They simulate Daphnia enzymes and show that plankton Crustacea have complete enzyme mechanisms for digestion of particulate food.