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

Leonardo J Magnoni; Juan Antonio Martos-Sitcha; Augusto Queiroz; Josep Alvar Calduch-Giner; José Fernando Magalhães Gonçalves; Cristina M R Rocha; Helena T Abreu; Johan W Schrama; Rodrigo O A Ozorio; Jaume Pérez-Sánchez

doi:10.1242/bio.024299

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

Biol Open. 2017 Jun 15;6(6):897-908. doi: 10.1242/bio.024299.

Authors

Affiliations

¹ CIIMAR, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, Matosinhos 4450-208, Portugal.
² IIB-INTECH, Av. Intendente Marino Km. 8.2, Chascomús 7310, Argentina.
³ Nutrigenomics and Fish Growth Endocrinology Group, Institute of Aquaculture Torre de la Sal (CSIC), Ribera de Cabanes, Castellón 12595, Spain.
⁴ ICBAS, University of Porto, Rua de Jorge Viterbo Ferreira n.° 228, Porto 4050-313, Portugal.
⁵ REQUIMTE, LAQV, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, Porto 4200-465, Portugal.
⁶ ALGAplus, Lda., Travessa Alexandre da Conceição S/N, Ílhavo 3830-196, Portugal.
⁷ Aquaculture and Fisheries group, WIAS, Wageningen University, AH Wageningen 6700, The Netherlands.
⁸ CIIMAR, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, Matosinhos 4450-208, Portugal rodrigo.ozorio@ciimar.up.pt.

Abstract

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.

Keywords: Hypoxia; Nutritional background; Oxidative stress; Sea bream; Seaweeds.