The toxic effect of an oxylipins-containing macroalgae extract on sea urchin reproduction and development

Abstract

Background - Algae possess complex and highly evolved chemical defenses against their grazers, including the production of bioactive molecules such as oxylipins. Ericaria brachycarpa, a canopy-forming brown algae, contribute to form the habitat in the Mediterranean Sea for the sea urchin species Arbacia lixula. The aim of this work was to evaluate the effects of an oxylipins-containing extract from E. brachycarpa on the reproduction and development of A. lixula, evaluating the fertilization success and the embryotoxic activity from fertilization (0 h) to the pluteus stage (72 h). Methods - The extract was tested in gametes to test the fertilization success and at three developmental endpoints (zygote, gastrula and pluteus). The range of concentrations tested was chosen to cover a full 0-100 % abnormality curve, with doses ranging from 0 to 40 μg/mL. Results – We found a strong dose-dependent effect on the fertilization success and on development. Gastrulae were the most sensitive to the extract with the lowest EC50. At low doses we found an impairment in development and biomineralization, while the highest concentration tested caused 100% mortality of the embryos at all stages. Western Blot experiments showed the modulation of different molecular markers (HSP60, LC3, p62, CHOP and cleaved caspase-7), indicating enhanced autophagy at low concentrations and apoptosis at high concentrations. The TUNEL assay confirmed high levels of fragmented DNA. Conclusion - These data support the hypothesis that macroalgae may exert a sort of population control against their grazers, releasing in the marine environment toxic compounds, such as oxylipins, following their tissue disruption by sea urchins and other grazers. Project funded by the European Union – NextGenerationEU under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2, Project NBFC CUP B73C22000790001