In calanoid copepods it is poorly understood how enzymatic
activities and patterns are affected by abiotic and biotic
factors. Such knowledge, however, is crucial to assess metabolic
functioning and performance of organisms in different habitats.
Therefore, our study focuses on digestive enzyme activities in
relation to temperature, pH and food in the Arctic species
Calanus glacialis and in Centropages hamatus and Temora
longicornis from the North Sea. Enzyme activities were measured
over a range from 0 to 70 °C (lipases/esterases, proteinases)
and pH 5 to 9 (proteinases). In all species, relative
proteinases activity peaked at 40/50 °C and pH 6; relative
lipases/esterases activity peaked at 30 °C. Between 0 and 20 °C,
lipase activity of C. glacialis was higher (40-70% of maximum)
than that of the boreal copepods (25-64%), which suggests
thermal adaptation of the lipid metabolism in the polar species.
Incubating C. glacialis with the diatom Thalassiosira
weissflogii showed (i) that enzyme activities increased