We investigated ontogenetic variations in dry mass and nucleic acid contents of the planktonic crustacean Artemia salina. Individual contents of DNA and RNA increased exponentially with incubation day and developmental stage, except for newly-hatched nauplii. High variability was found in the temporal and ontogenetic patterns of dry (DW) and ash-free dry weights (AFDW) due to the mixture of different ages and stages, and thus RNA/DNA ratios were not significantly associated with weight-specific growth rates. RNA/DNA and AFDW/DNA ratios decreased from newly-hatched naupliar to middle post-metanaupliar stages, but AFDW/DNA ratios decreased while RNA/DNA ratios increased from late post-metanaupliar stages. These results suggest that nucleic acid ratios are not the optimal indicator for evaluation of weight-specific growth rates when there is high variability in body mass, but that a combination of RNA/DNA and AFDW/DNA ratios can be indicative of important stages in ontogenetic development, such as indicating yolk consumption of newly hatched nauplii and gonad maturation in late life stages of A. salina.