Impact of the diatom oxylipin 15S-HEPE on the reproductive success of the copepod Temora stylifera

Abstract

The copepod Temora stylifera was fed with the pennate diatom Pseudo-nitzschia delicatissima for 15 days. This diatom does not produce polyunsaturated aldehydes (PUAs) but only synthesizes other oxylipins such as the hydroxyacid (5Z,8Z,11Z,13E,15S,17Z)-15-hydroxy-5,8,11,13,17-eicosapentaenoic acid (15S-HEPE). Effects of this monoalgal diet were compared to copepods fed with the PUA-producing diatom Skeletonema marinoi and the control dinoflagellate Prorocentrum minimum which does not produce any oxylipins. Both egg production and hatching success were negatively affected by the two diatoms compared to the control diet. Both diatoms also induced malformations in the offspring, with the number of malformed nauplii increasing dramatically with time. Malformed nauplii were apoptotic (TUNEL-positive) indicating imminent death. In terms of recruitment, only 4 healthy nauplii female -1 day -1 with S. marinoi and 9 healthy nauplii female -1 day -1 with P. delicatissima were produced during the 15-day experimental period. The results indicate that P. delicatissima induced negative effects comparable to those of S. marinoi even though it did not produce PUAs. This is the first study that tests the biological activity of oxylipins other than PUAs on copepod reproduction.

Non-volatile oxylipins can render some diatom blooms more toxic for copepod reproduction

“…In 2005, total oxylipin levels were three times as high as in 2004, providing an explanation for the almost 25% reduction in hatching success in 2005 compared to 2004. These findings support laboratory studies (Barreiro et al, 2011;Fontana et al, 2007;Ianora et al, 2011b) showing that NVOs can induce negative effects comparable to those of PUAs. What remains unknown is why NVO levels in the phytoplankton vary from year-to-year.…”

“…One of these compounds, 15S-HEPE, acts similarly to PUAs in that it induces malformations in newlyhatched nauplii and arrests embryogenesis at elevated concentrations (Ianora et al, 2011b). Interestingly, many diatom species seem to produce only these NVOs and not PUAs (Barreiro et al, 2011;Cutignano and Lamari, 2011;d'Ippolito et al, 2009;Fontana et al, 2007;Nanjappa et al, 2014).…”

Responses of the estuarine copepod Pseudodiaptomus annandalei to diatom polyunsaturated aldehydes: Reproduction, survival and postembryonic development

“…Teratogenic impacts (birth defects and hatching of malformed larvae) have also been recorded when females are fed with certain diatom diets (Poulet et al, 1995(Poulet et al, , 2007Uye, 1996;Ianora et al, 2011). In our study, 45-93% reduction was observed in nauplii production with increasing concentrations of decadienal.…”

“…Previous studies have reported that exposure of embryos and larvae to PUA can severely impact development, growth and fitness of other copepod species (Miralto et al, 1999;Caldwell et al, 2002;Carotenuto et al, 2002;Ianora et al, 2004Ianora et al, , 2011Vargas et al, 2006;Poulet et al, 2007;Kâ et al, 2014). Decadienal has also been shown to potentially impact other marine organisms (Romano et al, , 2010Caldwell et al, 2005;Tosti et al, 2003).…”

Design and Synthesis of Pro-Apoptotic Compounds Inspired by Diatom Oxylipins

“…In agreement with previous studies on copepod nauplii reported in [12], this metabolite inhibited the cleavage in sea urchin Paracentrotus lividus embryos at concentrations higher than 70 µM and induced 100% blockage of cellular division at 94 µM (Figure 1a). Nevertheless, the methyl ester of 15( S )-HEPE ( 2 ) showed a noticeably higher activity (IC50 = 4.1 µM) and completely arrested division of treated embryos at only 8 µM.…”