Aquaculture Europe 2023

September 18 - 21, 2023


Add To Calendar 20/09/2023 16:30:0020/09/2023 16:45:00Europe/ViennaAquaculture Europe 2023EFFECTS OF DIETARY IRON SUPPLEMENTATIONON BIOSYNTHESIS OF LONG-CHAIN POLYUNSATURATED FATTY ACIDS IN THE NEREID POLYCHAETE Hediste diversicolorStrauss 2The European Aquaculture Societywebmaster@aquaeas.orgfalseDD/MM/YYYYaaVZHLXMfzTRLzDrHmAi181982


A. Villena-Rodríguez1* , Ó. Monroig1, F. Aguado-Giménez2, J. Pérez1 , M. Lizanda1, I.E. Martín2, I. Varo1, I. Rasines2  and J.C. Navarro1


1 Instituto de Acuicultura Torre de la Sal (IATS), CSIC, 12595 Ribera de Cabanes, Castellón, Spain . Email: .  2  “El Bocal ” Marine Aquaculture Plant, Oceanographic Centre of Santander (COST_IEO), CSIC, Monte_Corbanera ,  39012 Santander, Spain



 Multiple aquatic invertebrates have the necessary enzymatic machinery for de novo biosynthesis of long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA) including the so-called “omega-3” EPA (20:5n-3) and DHA (22:6n-3) . Two distinct types of fatty acyl desaturases, namely methyl-end (ω des) and front-end desaturases (Fed), are known to be involved in animals’ LC-PUFA biosynthesis [1]. Iron (Fe) has a prominent role in LC-PUFA biosynthesis since  it is a cofactor of desaturases, and is present in the active di-iron centres of all aerobic desaturases [2]. Since  expression of desaturases involved in  LC-PUFA biosynthesis can be  increased by feeding a  low LC-PUFA diet, an innovative strategy to enhance the endogenous production of LC-PUFA in aquatic organisms consists of dietary Fe supplementation  to guarantee adequate supply under conditions resulting in desaturase activation .  Supplementation of Fe has been shown to positively influence LC-PUFA biosynthesis in salmonids  [3] but, to the best of our knowledge, has not been yet investigated in invertebrates. The present study aimed to assess dietary Fe supplementation as an enhancer of LC-PUFA biosynthesis in the  nereid polychaete Hediste diversicolor, a commercially important species with great interest for aquaculture.

Materials and Methods

 First, an in vitro trial was carried out by growing t ransgenic yeast expressing the H. diversicolor desaturases (two  ω des and two Fed) in the presence of specific fatty acid  (FA) substrates. For each desaturase , the following treatments were tested: no Fe supplementation (control), supplementation with FeSO4 (inorganic Fe), supplementation with ProPath® Fe (organic Fe) , and supplementation with an Fe chelating agent (chelator) . The desaturase activity of transgenic yeast was estimated by  calculating the conversion of the FA substrate into the FA product.  Second, an in vivo trial with  H. diversicolor juveniles was carried out. Briefly, 20 worms (25-50 mg ww) were randomly distributed in nine experimental units (3 units x 3 diets) .  The worms were fed for  7  weeks  on an experimental diet with low LC-PUFA (control) , which was supplemented with  either FeSO4 (inorganic Fe ) or ProPath® Fe ( organic Fe). Worms were fed to 4%  of the biomass 5 d per week.  Survival and specific growth rate ( SGR) were recorded. After 7 weeks, the animals were starved for 24h prior sampling for lipid analysis.  Total lipids were extracted and quantified gravimetrically,  with  an aliquot being transmethylated to fatty acid methyl esters (FAME), and analysed using gas chromatography. The results were processed using principal component analysis (PCA).  FA analyses from yeast (in vitro assay)  were  carried out as described above for worm samples .

Results and Discussion

 In the  in vitro  trial  all the  H. diversicolor  desaturases converted the specific FA substrate into the corresponding product with i norganic and  organic Fe treatment  exhibiting higher enzyme activity than control . The Fe c helating agent reduced the activity of al desaturases (Figure 1a).  These results suggest that Fe can effectively enhance desaturase activity as previously reported in yeast [4].  At the end of the experiment, no significant differences (p>0.05) in SGR (average of 0.084) nor s urvival (96.1±4.2 %)  were found among treatments. Moreover, t he results from the in vivo trial did not show  any clear effect of organic and in organic Fe supplementation on the FA composition of  H. diversicolor  whereas a clear segregation of the day 0 samples was found (Figure 1b). High levels of 18:1n-9 and 18:2n-6 (23.6 and 19.3%, respectively) on the FA profile of all treatments were found , suggesting a strong dietary effect (34.4 and 15.4%, respectively). Besides, in all treatments,  the FA composition of polychaetes showed high levels of PUFA (33.4%) such as 20:4n-6 (ARA), EPA and DHA, indicating bioconversion and trophic upgrading.  The reasons underlying the apparent discrepancy between the enhanced desaturase activity observed in vitro and the lack of increased LC-PUFA biosynthesis in worms fed on Fe supplemented diets (in vivo trial)  remain unclear. However,  it is reasonable to speculate that  the Fe enhancing effect on LC-PUFA biosynthesis could not be detected in the present study due to an insufficient capacity of experimental diet to  increase the  expression of fatty acyl desaturases in vivo.  Further analyses on gene expression, as well as  FA composition  of the polar and neutral lipid fractions,  will  contribute to clarify  the role that dietary Fe supplementation  may  play  as enhancer of LC-PUFA biosynthesis in  H. diversicolor.


 This study forms part of the ThinkInAzul programme and was supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and by Generalitat Valenciana (THINKINAZUL/2021/26). Additional funding was received from the project "SPACE” (TED2021-129647B-I00), fund ed by MCIN/AEI /10.13039/501100011033 and by European Union NextGenerationEU/ PRTR. We thank Zinpro Corporation for supplying ProPath ® Fe for the experimental diets .


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  2.  Shanklin, J.; Guy, J.E.; Mishra, G.; Lindqvist, Y. Desaturases: Emerging models for understanding functional diversification of diiron-containing enzymes. J. Biol. Chem . 2009, 84, 18559–18563
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  4.  Pádrová, K.; Čejková, A.; Cajthaml, T.; Kolouchová, I.; Vítová, M.; Sigler, K.; Řezanka, T. Enhancing the lipid productivity of yeasts with trace concentrations of iron nanoparticles.  Folia Microbiol.  2016, 61, 329–335.