Combined effects of elevated temperature and fluoxetine exposure on early development of the sea urchin Paracentrotus lividus

Temperature rise associated with climate change increases the vulnerability of coastal species, which are also exposed to pharmaceuticals. We investigated the effects of thermal stress and fluoxetine (FLX), alone and in combination, on early developmental stages of the sea urchin Paracentrotus lividus, a key coastal species. Gametes, zygotes and embryos were exposed to ambient (18°C) and near-future projections (21°C, 24°C) to identify the most sensitive developmental stage to warming. In parallel, environmentally relevant FLX concentrations were tested under near-future temperature scenarios. Fertilization and embryonic development were not affected by any treatment, conversely to larval development. Larvae derived from zygotes exposed to elevated temperature, alone or combined with FLX, exhibited developmental anomalies, while reductions in body width and post-oral arm gap were found in larvae from all exposed stages under elevated temperature. Zygote was the most thermally sensitive stage, and warming enhanced FLX-related effects, reducing larval development. These findings highlight that the interaction between ocean warming and pharmaceutical contamination may increase the vulnerability of early life stages of coastal species, potentially affecting survival under future climate scenarios.