Medium term time acclimation of feeding and digestive enzyme activity in marine copepods: influence of food concentration and copepod species

Abstract

Inter-species differences in the acclimation strategy of the nutritional processes (ingestion, digestive enzyme activity) of female and copepodite stage V copepods were established for Acartia clausi, Eurytemora herdmani and Drepanopus pectinatus. Under food limiting conditions, Acartia-type copepods (low level of energy reserve, high turnover of its biomass) displayed positive acclimation of both ingestion rate and digestive system. Under the experimental conditions used, both A. clausi and E. herdmani required 48 h to significantly acclimate their digestive activity to changes in food ration exceeding 1 μg C copepod-1. Inter-species differences agree with the hypothesis that internal control of the acclimation process is governed by the metabolic requirement of the animals. Also, the differential response of D. pectinatus collected before and after a phytoplankton bloom suggests an important role for past feeding conditions (physiological memory), explaining the variability in responses between natural field conditions and laboratory conditions. Physiological adaptation is proposed as a mechanism which minimizes the effect of stressful trophic conditions. -from Authors