Sea urchin eggs contain a plastid-derived structure that contributes to their development.

Development in the sea has long been thought to be a nutritional gamble that disproportionately ends in starvation. Here, we support the premise that components of plastids appear to be incorporated into sea urchin eggs and that these, in turn, benefit development. We find chromoplast-derived carotenoid crystals and chromoplast-specific metabolites inside the eggs of the sea urchin Arbacia lixula. We find evidence of plastid DNA in the eggs of 11 other sea urchins, with diatoms being the primary source and taxonomic richness of these plastid taxa directly related to egg size. The light-dependent activity of these chromoplast components influences phytohormone and lipid metabolism as well as offspring development, morphological plasticity, and survival. Offspring that benefit from these chromoplast components are predicted to disperse further, over larger geographic areas, and use a wider range of currents, including those that cross ocean basins. Data presented here challenge the long-held belief that components of non-metazoan organelles are unable to enter the germline and be passed between generations. We hypothesize that sea urchins manipulate plastids solely for their self-interest with the result of this process being a novel and adaptive form of maternal provisioning.