Simple SummarySimultaneous hermaphrodites mainly adjust their reproductive resources according to mating opportunities. Numbering among other factors in the overall energy budget of hermaphrodites are life–history traits of species, environmental conditions and stressors. All such factors may influence the allocation of reproductive resources in hermaphrodites and the trade-off between sexual functions. Here, we investigated the trade-off between food deprivation and the investment of resources in female allocation and somatic growth in the simultaneous hermaphroditeOphryotrocha diadema, a polychaete worm, by exposing focal individuals to three different nutritional regimes. Our findings show the marked influence of nutritional stress on female allocation and body growth rate.AbstractHermaphrodites are characterized by plastic sex allocation, by which they adjust their allocation of reproductive resources according to mating opportunities. However, since the plasticity of sex allocation is influenced by environmental conditions, it may also be affected by species-specific life–history traits. In this study, we explored the trade-off between nutritional stress due to food deficiency and the investment of resources in female allocation and somatic growth in the simultaneously hermaphroditic polychaete worm,Ophryotrocha diadema. To achieve this, we exposed adult individuals to three food supply levels: (1) ad libitum—100% food supply, (2) intense food deficiency—25% food resources, and (3) extreme food deficiency—0% food resources. Our findings show a progressive decrease in female allocation in the numbers of cocoons and eggs and in body growth rate ofO. diademaindividuals as the level of nutritional stress increased.