EGG SIZE, OFFSPRING QUALITY AND FOOD LEVEL IN PLANKTONIC ROTIFERS

1. For two species of planktonic rotifers, Brachionus calyciflorus and Synchaeta pectinata, neonates from larger eggs were more resistant to starvation than neonates from smaller eggs, so egg size was positivel y correlated with offspring quality. 2. Theories of optimal offspring size in zooplankton predict either a decrease in offspring size with i ncreasing food level, or maximum offspring size at intermediate food l evels. In experiments using acclimated, even-aged individuals, neither rotifer species changed its egg size as predicted by theory. B. calyc iflorus egg size increased with increasing food concentration, while S . pectinata egg size did not change. 3. The lack of fit to theory may have occurred because of constraints on minimum or maximum egg size, c onstraints on total reproductive effort, or because offspring fitness is influenced by traits in addition to neonate starvation time.