Nucleic acids as growth rate indicators for early developmental stages of Calanus pacificus Brodsky

Abstract

Relationships among RNA and DNA contents, dry weight, and growth rate were investigated for the copepod Calanus pacificus Brodsky cultured under different temperature and food conditions. For a given culture condition, RNA/mg dry wt, RNA/DNA, and RNA/ animal tended to be positively, although weakly, correlated with growth rate. Copepods cultured at low temperature (8 °C), however, had higher RNA contents than faster growing animals from higher temperature (15 °C). Moreover, animals from low-temperature, high-food and high-temperature, low-food cultures had similar growth rates but markedly different levels of RNA. We conclude that the underlying relationships among nucleic acid contents and ratios, food, temperature, organism size, and developmental stage are too complex and contradictory for nucleic acids to be useful indicators or predictors of Zooplankton growth rates under field conditions.