(Annelida: Polychaeta)1

SYNOPSIS. The degree to which a female partitions resources between fecundity and per offspring investment is a central question in life-history theory. Maternal effects may influence the nature of this tradeoff through their effect on per offspring investment and subsequent offspring fitness. The purpose of this study was to determine the effect of female age and size on brood size (number of offspring), per offspring investment, and fitness in the polychaete Streblospio benedicti. Early stage embryos were collected from brooding females of known age and size over a period of 100 days; these embryos were counted and analyzed for their C and N content. Female size had a positive effect on brood size; larger females produced larger broods. However, brood size decreased with female age (females did not increase in size after reaching sexual maturity). Brood size declined 20-46 % between 60 and 160 days of age. During this same age period per offspring investment, measured in terms of C and N, in-creased by 25%. Offspring survivorship and size at two weeks post-re