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Biol Open. 2017 May 11. pii: bio.024299. doi: 10.1242/bio.024299. [Epub ahead of print]

Dietary supplementation of heat-treated Gracilaria and Ulva seaweeds enhanced acute hypoxia tolerance in gilthead seabream (Sparus aurata).

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CIIMAR, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4450-208 Matosinhos, Portugal.
IIB-INTECH, Av. Intendente Marino Km. 8.2, 7310 Chascomús, Argentina, South America.
Nutrigenomics and Fish Growth Endocrinology Group, Institute of Aquaculture Torre de la Sal (CSIC), 12595 Ribera de Cabanes, Castellón, Spain.
ICBAS, University of Porto, Rua de Jorge Viterbo Ferreira n.º 228, 4050-313 Porto, Portugal.
REQUIMTE, LAQV, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
ALGAplus, Lda., Travessa Alexandre da Conceição S/N, 3830-196 Ílhavo, Portugal.
Aquaculture and Fisheries group, WIAS, Wageningen University, 6700 AH Wageningen, The Netherlands.
CIIMAR, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4450-208 Matosinhos, Portugal


Intensive aquaculture practices involve rearing fish at high densities. In these conditions, fish may be exposed to suboptimal dissolved O2 levels with an increased formation of reactive O2 species (ROS) in tissues. Seaweeds (SW) contain biologically active substances with efficient antioxidant capacities. This study evaluated the effects of dietary supplementation of heat-treated SW (5% Gracilaria vermiculophylla or 5% Ulva lactuca) on stress bioindicators in seabream subjected to a hypoxic challenge. One hundred and sixty-eight fish (104.5 g each) were distributed in 24 tanks, in which eight tanks were fed one of three experimental diets for 34 days: a control diet without SW supplementation (i), or a control diet supplemented with Ulva (ii) or with Gracilaria (iii). Thereafter, fish from 12 tanks (n= 4 tanks/dietary treatment) were subjected to 24 h hypoxia (1.3 mg O2 l-1) and subsequent recovery normoxia (8.6 mg O2 l-1). Hypoxic fish showed an increase in hematocrit values regardless of dietary treatment. Dietary modulation of the O2-carrying capacity was conspicuous during recovery, as fish fed SW supplemented diets displayed significantly higher haemoglobin concentration than fish fed the control diet. After the challenge, survival rates in both groups of fish fed SW were higher, which was consistent with a decrease in hepatic lipid peroxidation in these groups. Furthermore, the hepatic antioxidant enzyme activities were modulated differently by changes in environmental O2 condition, particularly in seabream fed the Gracilaria diet. After being subjected to hypoxia, the gene expression of antioxidant enzymes and molecular chaperones in liver and heart were down regulated in seabream fed SW diets. This study suggests that the antioxidant properties of heat-treated SW may have a protective role against oxidative stress. The nature of these compounds and possible mechanisms implied are currently being investigated.


antioxidants; hypoxia; nutritional background; oxidative stress; seabream; seaweeds

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