Respiration and nitrogen excretion of zooplankton. IV. The influence of starvation on the metabolism and the biochemical composition of some species

Changes in the respiration, ammonia excretion and biochemical composition were studied for three species of starving zooplankton (Calanus finmarchicus, Sagitta elegans, and Acartia clausi). Over the period of starvation, the respiration rate of all three species followed the same pattern of an initial decrease followed by a more or less constant level. A similar pattern was observed for the ammonia excretion rate of S. elegans and A. clausi, whereas C. finmarchicus excretion appeared to oscillate between high and low levels of protein catabolism. Study of the biochemical changes showed that C. finmarchicus consumed primarily lipids, and at times proteins, to meet its energy requirement whereas S. elegans and A. clausi primarily used protein. Variations in the elemental composition as well as the O:N ratio confirmed that C. finmarchicus alternated between periods of protein-dominant catabolism and lipid-dominant catabolism during starvation. No similar change in catabolism was observed in the two other species. The results are discussed in terms of physiological mechanisms of resistance to starvation and were used to calculate the energy budget of S. elegans and C. finmarchicus during the period of total starvation. The significance of such budgets is discussed and some of the sources of error examined.Bedford Institute of Oceanography Contribution.