Dietary supplementation of heat-treated Gracilaria and Ulva seaweeds enhanced acute hypoxia tolerance in gilthead sea bream (Sparus aurata).
Magnoni, L. J., Martos-Sitcha, J. A., Queiroz, A., Calduch-Giner, J. A., Goncalves, J. F. M., Rocha, C. M. R., Abreu, H. T., Schrama, J. W., Ozorio, R. O. A. and Perez-Sanchez, J.
CIIMAR, University of Porto, Terminal de Cruzeiros do Porto de Leixoes, Av. General Norton de Matos s/n, Matosinhos 4450-208, Portugal.
IIB-INTECH, Av. Intendente Marino Km. 8.2, Chascomus 7310, Argentina.
Nutrigenomics and Fish Growth Endocrinology Group, Institute of Aquaculture Torre de la Sal (CSIC), Ribera de Cabanes, Castellon 12595, Spain.
ICBAS, University of Porto, Rua de Jorge Viterbo Ferreira n. degrees 228, Porto 4050-313, Portugal.
REQUIMTE, LAQV, Departamento de Engenharia Quimica, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, Porto 4200-465, Portugal.
ALGAplus, Lda., Travessa Alexandre da Conceicao S/N, Ilhavo 3830-196, Portugal.
Aquaculture and Fisheries group, WIAS, Wageningen University, AH Wageningen 6700, The Netherlands.
CIIMAR, University of Porto, Terminal de Cruzeiros do Porto de Leixoes, Av. General Norton de Matos s/n, Matosinhos 4450-208, 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 sea bream subjected to a hypoxic challenge. 168 fish (104.5 g average weight) were distributed in 24 tanks, in which eight tanks were fed one of three experimental diets for 34 days: (i) a control diet without SW supplementation, (ii) a control diet supplemented with Ulva, or (iii) a control diet with Gracilaria 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 sea bream 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 sea bream 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.
Biol Open 6(6): 897-908 (2017)