Relationship between specific dynamic action and protein deposition in calanoid copepods

The link between specific dynamic action (SDA) and protein deposition was i nvestigated in copepodites stage V of two calanoid copepod species, the ner itic Acartia tonsa and the oceanic Calanus finmarchicus. This was done by m easuring respiration before, during, and after a specific feeding period an d measuring the incorporation of carbon into proteins. These were also meas ured on individuals incubated with cycloheximide, an antibiotic that inhibi ts protein synthesis. The cycloheximide treatment significantly diminished the magnitude of SDA in both A. tonsa and C. finmarchicus, and inhibited ca rbon incorporation into protein in both species. This provides evidence tha t the rate at which protein deposition takes place greatly affects the magn itude of SDA. The specific respiration rates of both starving and feeding c opepods were generally higher in A. tonsa than in C. finmarchicus. This inf luenced SDA, the magnitude of SDA normalised to an 8 h feeding period being threefold higher in A. tonsa (78.7+/-25.7 nlO(2) mu gC(-1)) than in C. fin marchicus (27.5+/-11.6 nlO(2) mu gC(-1)). This difference may arise due to differences in energy allocation in the organisms of the copepodite V stage of the two species. In this stage C. finmarchicus deposits large quantitie s of storage lipids, predominately wax esters, whereas A. tonsa deposits pr oteins during somatic growth. (C) 2000 Elsevier Science B.V. All rights res erved.