Assessment of Calanus finmarchicus growth and dormancy using the aminoacyl-tRNA synthetases method

We obtained growth rates of the copepod Calanus finmarchicusat different locations across the North Atlantic between May1998 and June 2004. Animals were incubated for 2–9 daysand fed either with natural food assemblages or with culturedalgae. During this period, we measured both somatic weight-specificgrowth rates (measured as protein change) and aminoacyl-tRNAsynthetases (AARS) activity. We found a highly significant relationshipbetween AARS activity and growth in protein content (R² = 0.55,P < 0.001). Significant AARS activity also occurred whengrowth was negative, the relationship predicting an AARS activitylevel of 8.33 nmPPi·mg protein^–1·h^–1when somatic growth is zero. This is because AARS activity isexpected even when growth is negative, owing to the continuedprotein turnover in the cells. The AARS method allowed for thefirst time the study of protein metabolism in overwinteringC. finmarchicus. Our study results showed that overwinteringcopepods had significantly lower values of AARS activity thannon-diapausing animals (t = –3.51, P < 0.002). TheAARS method opens the possibility to better understand physiologydynamics of deep-water organisms (e.g. the beginning and endof diapause).