Nucleic acids and growth of Calanus finmarchicus in the laboratory under different food and temperature conditions

• Published in: Marine Ecology Progress Series
• Main Authors: Wagner, Melissa M., Campbell, Robert G., Boudreau, Carla A., Durbin, Edward G.
• Format: Text
• Language: unknown
• Published: DigitalCommons@URI 2001
• Subjects: Calanus finmarchicus; Copepods
• Online Access: https://digitalcommons.uri.edu/gsofacpubs/320; https://doi.org/10.3354/meps221185; https://digitalcommons.uri.edu/context/gsofacpubs/article/1327/viewcontent/Wagner_etal_NucleicAcids_2001.pdf

We examined the effects of food concentration and temperature on nucleic acids and protein content of Calanus finmarchicus in order to evaluate the use of RNA as a growth rate index for this species. We measured RNA, DNA, and protein content of copepods reared from egg to adult stage in 5 combinations of food and temperature conditions (25 to 500 µg C l-1, 4 to 12°C). At 8°C, DNA, RNA and protein content and RNA:DNA differed among food treatments during Stages N6 through to adult female. Protein:DNA ratios and RNA:protein ratios were significantly different among food levels for only 3 of the 8 stages examined. At excess food, DNA, RNA, and protein content and RNA:DNA ratios were inversely related to temperature for most stages from C1 onward, but the effect of temperature was relatively small over the range of temperatures investigated. The RNA:DNA and protein:DNA ratios increased with developmental stage whereas the RNA:protein ratio and growth rates (measured in terms of protein, nitrogen, DNA, and carbon content) declined with increasing stage. Although the relationship of RNA:DNA to growth rates was stage-specific, the two were related when standardized for temperature and developmental stage. RNA:protein ratios were directly related to growth rates regardless of stage, and the slope of the relationship increased with increasing temperature in a nonlinear fashion. Our results emphasize the importance of temperature and developmental stage for the relationship of growth rates to RNA concentration and RNA:DNA ratios. We propose 2 ways to estimate in situ growth rates of C. finmarchicus from RNA:DNA or RNA:protein ratios and environmental temperature