Abstract
Oxylipins such as polyunsaturated aldehydes (PUAs) and hydroxyacids (HEPEs) are signaling molecules derived from the oxidation of polyunsaturated fatty acids. They are common in diatoms that constitute a major group of microalgae in freshwater and oceanic ecosystems. Although HEPEs represent the most common oxylipins produced by diatoms, little information is available on their effects on marine invertebrates, and most of the information has been obtained by testing individual HEPEs. Our previous studies reported that four hydroxyacids, i.e., 5-, 9-, 11-, and 15-HEPE, were able to induce malformations and a marked developmental delay in sea urchin Paracentrotus lividus embryos, which had not been reported for other oxylipins. Here, we tested a mixture of 5-, 9-, 11-, and 15-HEPE at different concentrations for the first time. The results showed that mixtures of HEPEs have synergistic effects that are much more severe compared to those of individual HEPEs: The HEPE mixtures induced malformations in sea urchin embryos at lower concentrations. Increasing HEPE mixture concentrations induced a marked increase in the number of delayed embryos, until all embryos were delayed at the highest concentration tested. At the molecular level, the HEPE mixtures induced variations in the expression of 50 genes involved in different functional processes, mainly down-regulating these genes at the earliest stages of embryonic development. These findings are ecologically significant, considering that during diatom blooms, sea urchins could accumulate HEPEs in concentrations comparable to those tested in the present study.
Highlights
Oxylipins are oxygenated fatty acids derivatives distributed in a wide range of organisms, including plants [1] and algae [2], where they are involved in the regulation of several physiological processes [3,4]
Our work explored the noxious effects of diatom oxylipin mixtures, to which marine organisms are commonly exposed in their natural habitats
A previous study revealed that mixtures of the three polyunsaturated aldehydes (PUAs) decadienal, heptadienal, and octadienal acted in a synergistic way on sea urchin P. lividus embryonic development [22]
Summary
Oxylipins are oxygenated fatty acids derivatives distributed in a wide range of organisms, including plants [1] and algae [2], where they are involved in the regulation of several physiological processes [3,4]. In diatoms, these molecules are produced through an enzymatic cascade activated after cell breakage [5,6,7]. Mar. Drugs 2019, 17, x FOR PEER REVIEW acid derivatives with hydroxy-, keto-, oxo-, and epoxy functionalities [7,11,12]. Following the demonstration by Miralto et al.acid [13]derivatives that these with diatom secondary metabolites induced reproductive aldehydes (PUAs) and fatty hydroxy-, keto-, oxo-, and epoxy functionalities failure in copepods, other studiesby have identified these effects on a wide variety of [7,11,12]
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