Levels of protein, RNA, DNA, glycogen and lipid during growth and development of Daphnia magna Straus (Crustacea: Cladocera)

1. Protein, RNA, DNA, glycogen and lipid content were determined in Daphnia magna on days 0, 2, 4, 6, 8 and 21 of growth and development. The composition of D. magna as percentage of reconstituted dry weight was similar to other zooplankton with the exception of DNA content, which was lower than values previously reported.
2. The relative content of protein, RNA, DNA and reconstituted dry weight changed during the 21-day growth period, and these changes were related to growth rate and total growth of D. magna . RNA:protein, RNA: reconstituted dry weight, and protein:RNA : DNA ratios were highly correlated to relative growth rate and total growth as measured by protein content or reconstituted dry weight.
3. Addition of progeny biomass to adult biomass increased correlations between biochemical ratios and absolute growth rate, but had little effect on relationships involving relative growth rate or total growth.
4. The relationship between biomolecule ratios and growth established for D. magna grown under optimal conditions was not successful in predicting growth of D. magna reared under crowded conditions.
5. These data indicate that variation in biochemical ratios among life, stages of D. magna may be used to predict growth of organisms grown under similar conditions, but may not be extended to other situations. It is suggested, however, that variation in biochemical ratios in a particular life stage of a zooplankton species may be related to the productivity for that species.