Marine heatwaves have no impact on fertilization, early development and sensitivity to metal toxicity in the sea urchin Paracentrotus lividus

Marine Heatwaves (MHWs) have become more severe and frequent worldwide under global warming. They are projected to intensify under different climate scenarios, with unknown consequences for the marine biota. In this study we assess the impact of MHWs on the early developmental stages of the Mediterranean sea urchin Paracentrotus lividus, by analyzing fertilization rate, larval development, and growth from adults sampled in the 2021-2025 timeframe during natural MHW events and during periods without MHWs. We tested the assumption that naturally MHW-exposed parents would produce more sensitive offspring to thermal stress in terms of fertilization success, larval development, and growth morphology. In addition, we evaluated larval sensitivity to a reference contaminant (copper) through embryotoxicity assays. Fertilization and early development were not affected by MHWs. Conversely, in response to parental MHW-exposure, larval growth featured an increase in body width, total body length, and postoral arms's gap. Sensitivity to metals did not increase in larvae from MHW-exposed parents, suggesting a tolerance to thermal events. In the current context of increasing temperature anomalies, this study reveals the adaptability and plasticity of sea urchin larvae derived from adults exposed to natural MHW conditions, suggesting that coastal species are able to cope with extreme heat events.