On the nutrition and metabolism of zooplankton. V. Feeding efficiency ofCalanus finmarchicus

Nitrogen retained and nitrogen excreted by Calanus finmarchicus (Gunnerus) have been measured at all stages of development from egg to adult; and the percentage of food digested by adult females grazing algal diets has been estimated by two separate methods. The data have been used to calculate gross efficiency of growth by the young stages as well as that of egg-production by the adult female. They show that during a life-span of approximately ten weeks the animal uses 24% of the nitrogen it captures as food in order to build new tissue and produce eggs; the remaining larger fraction is lost as faecal pellets, moults and excreted end-products of metabolism.