Feeding, metabolism and body composition of the Antarctic copepod Calanus propinquus Brady with special reference to its life cycle

In the Weddell Sea, several biochemical and physiological characteristics of copepodite stage III to adult females of Calanus propinquus from the surface layer (0–100 m) and the deep layer (500–1,000 m) were compared at a time of high phytoplankton abundance (February) and a month later, when chlorophyll concentration was much lower and older copepodite stages had migrated to their overwintering depth. Daily rations of surface animals, estimated by the gut fluorescence method, varied from 0.8% to 7.8% body carbon (increasing with phytoplankton concentration). Respiration rate (calculated from measurements of electron-transport-system activity) and lipid and protein body content of animals inhabiting the surface layer decreased from February to April. Deep water animals (stage V and adult females) were characterized by high lipid and protein content; their respiration and excretion rates were much lower than in surface copepods. Our calculation showed that they could survive without an additional source of energy for 8–9 months. Based on our own and published data on bio-chemistry and physiology the possibility of a two-year life cycle is suggested.