In recent years, the Pacific brown macroalga Rugulopteryx okamurae has rapidly expanded across Mediterranean and Atlantic coasts, generating major ecological and socio‑economic impacts. In this study we examined the effects of exudates released by R. okamurae on the early developmental stages of two autochthonous sea urchin species, Paracentrotus lividus and Arbacia lixula , which are key benthic grazers in the invaded regions...