Dietary supplementation of heat-treatedGracilariaandUlvaseaweeds enhanced acute hypoxia tolerance in gilthead seabream (Sparus aurata)

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.

Using an integral projection model to assess the effect of temperature on the growth of gilthead seabream Sparus aurata

“…The LOS threshold is dependent on both the species and the water temperature, known to impact fish metabolic rate [ 24 , 61 ]. The lowest mean summer oxygen concentration observed in the lagoons (5.9 mg O 2 L -1 in Thau, 2006 –see S2 Fig ), is significantly greater than the limiting oxygen saturation (LOS) for this species (~2.3 mg O 2 L -1 at 19°C) [ 24 , 62 ]. It is therefore is unlikely that the S .…”

Somatotropic Axis Regulation Unravels the Differential Effects of Nutritional and Environmental Factors in Growth Performance of Marine Farmed Fishes

“…In hypoxic gilthead sea bream, this metabolic suppression is exemplified by the overall depression of catalytic, assembly, and regulatory enzyme subunits of complex I, II, III, and V of the mitochondrial respiratory chain, which is concurrent with the upregulation of catalytic and regulatory elements of complex IV (last electron donor to oxygen acceptor) ( 134 ). This dualism offers the possibility of a reduced but more efficient mitochondrial respiration during exposure or recovery from severe hypoxia, as has been shown, at least in part, in fishes fed with seaweed extracts as dietary surplus to protect against oxidative stress ( 140 ). Most of these metabolic readjustments, linked with endocrine disturbances ( 130 , 134 ), have been reported after exposure to severe hypoxia (18–19% oxygen saturation, 20–22°C) for 4 h under steady-state conditions, but most analyzed parameters require lasting periods to be responsive when the water O 2 concentration is fixed close to limiting oxygen saturation (LOS), defined as the threshold level where regulatory mechanisms are no longer sufficient to maintain the O 2 consumption rate with changes of the level of O 2 saturation ( 141 , 142 ).…”

Genome Sequencing and Transcriptome Analysis Reveal Recent Species-Specific Gene Duplications in the Plastic Gilthead Sea Bream (Sparus aurata)

“…These eurythermal and euryhaline characteristics, in combination with a notable resilience to aquaculture stressors, make this species a rather unique fish with a high plasticity to farming and challenging environments. This adaptation to varying culture conditions has been assessed in a number of physiological studies with focus on nutrition (Benedito-Palos et al, 2016;Simó-Mirabet et al, 2018;Gil-Solsona et al, 2019), chronobiology (Mata-Sotres et al, 2015;Yúfera et al, 2017), feeding behavior (López-Olmeda et al, 2009;Sánchez et al, 2009), stress (Calduch-Giner et al, 2010;Castanheira et al, 2013;Pérez-Sánchez et al, 2013;Bermejo-Nogales et al, 2014;Magnoni et al, 2017;Martos-Sitcha et al, 2017, 2019, or disease resilience (Cordero et al, 2016;Estensoro et al, 2016;Piazzon et al, 2018;Simó-Mirabet et al, 2018). However, the underlying genetic bases of this adaptive plasticity remain unknown.…”