Oithona is one of the most abundant marine planktonic copepod genera, and constitutes a major food source for fish larvae. While important advances have been attained on the ecology and metabolism of adults, little is known about the early developmental stages. In this work, we combined two biochemical indices, which were already used in calanoid copepods, to estimate growth and fitness of Oithona davisae nauplii and copepodites: i) the specific aminoacyl-tRNA synthetases (spAARS) activity (proxy of protein synthesis rate) and ii) the RNA/DNA ratio (indicative of overall metabolic activity). We provide a first insight into the variability of these parameters on O. davisae nauplii growing under different temperature and food conditions. Somatic growth rates (based on direct estimates of individuals’ length), spAARS activity and RNA/DNA ratio showed a positive correlation with temperature. The RNA/DNA ratio was more sensitive to starvation than the spAARS activity. Both the spAARS activity and RNA/DNA ratio are adequate indices of somatic growth. However, the RNA/DNA ratio relationships with both somatic growth rates and spAARS activity were different for nauplii and copepodites and hence might not be a suitable growth index for mixed populations. The methodological development presented simplifies the study of small copepod nauplii physiology

PICES-2012: Effects of natural and anthropogenic stressors in the North Pacific ecosystems: Scientific challenges and possible solutions, 12-21 October 2012, Hiroshima, Japan

Peer Reviewed