INFLUENCE OF FOOD AND TEMPERATURE ON LENGTHS AND WEIGHTS OF 2 MARINE COPEPODS

Recently captured CIIIs of Calanus glacialis Jaschnov were cultivated under four combinations of food (high and low) and temperature (almost-equal-to 3 and 12-degrees-C), and laboratory-reared CIs of Eurytemora herdmani Thompson and Scott were cultivated in excess food at almost-equal-to 3 and 10-degrees-C. Prosome lengths, estimated oil sac weights (OSW) and dry weights (total weight, TW, for E. herdmani; structural weight, SW, with oil sac removed, for C. glacialis) were obtained during development. Temperature significantly affected lengths, but not either SW or TW. In C. glacialis, food effects were highly significant on OSW, but not SW. Covariance analysis of length-weight regressions in both species confirmed the absence of food-temperature effects on SW or TW. Our results suggest that some of the controversy about food-temperature effects on size of copepods in nature results from inadequate distinction of different measurements of body size. Storage components, such as lipids, may reflect more direct effects of food supply, while "structural" tissue might remain unaffected. Temperature, on the other hand, may largely alter body volume rather than body mass.