Prenatal mortality in a marine cladoceran, Evadne nordmanni

Abstract

The embryology of the parthenogenetic marine cladoceran Evadne nordrnanni Loven is described such that an arbitrary series of developmental stages can be established. A population dynamics is developed for organisms that display the kind of paedogenesis seen in E. nordmanni, based on the assumption that the frequency of occurrence of a given developmental stage is an indicator of the time taken to complete it. It is then possible to determine the prenatal mortality. The equations are applied to samples of E. nordrnanni taken from the coastal waters of Nova Scotia. It is found that prenatal mortality plays a significant role in controlling the population size of E. nordrnanni. Evolutionary implications are discussed.