In this study, the effects of different diets on the survival and trypsin-like activity of a calanoid copepod Temora longicornis were investigated in the laboratory. The animals were starved or fed live algae (Diet A), a microencapsulated diet (Diet B), or the microencapsulated diet plus frozen algal cells (Diet C) for 10 days. The highest survival (69%) was obtained with those fed Diet A, whereas the lowest (11%) with the starved control (p<0.05). At the end of the experiment, animals fed Diet C displayed a significantly better survival (53%) than those fed Diet B (32%; p<0.05). Measurement of trypsin-like activity revealed that the animals adapted their digestive enzymes to live or dead algal cells more rapidly (within 24 h of feeding) than to formulated diet particles (after 5 days of feeding). The animals fed Diet A had the highest trypsin-like activity (p<0.05). Addition of frozen algal cells into the culture (Diet C) induced a significantly higher trypsin-like activity over Diet B fed animals (p<0.05). It seems that proteolytic enzymes of copepods feeding on artificial or live feeds have similar responses to other planktonic decapod crustaceans feeding at the primary consumer level
