When May Feeding Rates Cover Metabolic Expenses of Planktonic Nauplii?

Among planktonic copepods, which are the most abundant metazoa on our planet, nauplii represent a greater percentage in number than all later stages. While most nauplii do not possess the ability to perceive predators as well as later stages do, they have the additional disadvantage of higher metabolic needs (energy expenditure per unit body weight) than their older brethren. To determine metabolic expenditures of 3 species of calanoid nauplii (Eucalanus pileatus, Paracalanus quasimodo, Temora turbinata) we quantified their oxygen consumption and feeding rates simultaneously at different environmental food levels. As shown previously for adult females of planktonic copepods motion governs oxygen consumption and therefore the metabolic needs. Also, the type of motion matters. Because of major energy expenditures for motion nauplii of some calanoids can barely persist at low environmental phytoplankton levels. Therefore, we ask the question: Will temporary food shortages have similar effects as predation on the survival of calanoid nauplii? Our results should broaden our understanding on the effect of food limitation on the survival of planktonic nauplii.