Cortisol response to air exposure in Solea senegalensis post-larvae is affected by dietary arachidonic acid-to-eicosapentaenoic acid ratio

Abstract

An experiment was conducted in order to evaluate the effects of feeding frozen Artemia diets differing in arachidonic acid-to-eicosapentaenoic acid ratios (ARA/EPA) on growth, survival and stress coping ability of Senegalese sole post-larvae (19-31 days after hatch). Two experimental diets presenting high ('High'; 3.0) or low ('Low'; 0.7) ARA/EPA ratios were tested under two rearing conditions: undisturbed (C) and stressed by a 2-min air exposure every two days (S). Growth, survival and basal cortisol levels were similar between groups indicating that independently of dietary ARA/EPA ratios, fish were able to cope with the repeated stress imposed. Also, cortisol levels at 3 h past air exposure were determined in all groups at the end of the experiment. Among fish fed the 'Low' diet, C groups seemed to present a quicker recovery from the acute stress (basal-like levels) than S groups. Repeated stress effects were not apparent in fish fed the 'High' diet and, relative to basal levels, twofold higher cortisol concentrations were detected at 3 h, in both C and S groups. This study suggests the importance of ARA in steroidogenesis regulation and the modulatory role of EPA in this process. Despite the tolerance to a wide range of dietary ARA/EPA as indicated by growth and survival results, acute stress coping response may be more efficient in Senegalese sole post-larvae fed low ARA/EPA ratios and, under these particular conditions, a faster recovery of cortisol to basal values could be indicative of rearing conditions (undisturbed vs. repeatedly stressed).

Amending reduced fish‐meal feeds with marine lecithin, but not soy lecithin, improves the growth of juvenile cobia and may attenuate heightened responses to stress challenge

“…Similarly, whereas the cortisol response of cobia fed the 12% FM and 12% PL + Soy PL feeds was heightened relative to fish fed the 50% FM feed, the response of fish fed the 12% FM + Marine PL feed was intermediate between these groups. The importance of dietary phospholipid content in ensuring proper growth and development during early life history of fishes has been well-reviewed (Cotteau et al, 1997;Tocher et al, 2008;Cahu et al, 2009;Alves Martins et al, 2011), and cobia are known to require significant amounts of phospholipid during ontogeny. Niu et al (2008) observed that increasing dietary phospholipid increased growth and survival of advanced cobia larvae (initial weight = 0.4 g), ultimately concluding that the phospholipid requirement of this species may exceed 8% of the diet.…”

New developments and biological insights into the farming of Solea senegalensis reinforcing its aquaculture potential

“…Dietary effects, in particular the effect of ARA/EPA ratio, in the stress response of this species have also been investigated by Alves-Martins et al (2011). These authors observed a quicker recovery from an air exposure acute stress, but not from a repeated stress (determined as the return of cortisol to basal levels) when postlarvae were fed a low ARA/EPA ratio (0.7).…”

Influence of vegetable diets on physiological and immune responses to thermal stress in Senegalese sole (Solea senegalensis)

“…Montero et al [ 15 ] detected higher levels of cortisol in gilthead sea bream submitted to a stress induced by high stock density and fed a diet with 60 and 80% of FO substituted by lindseed oil. Furthermore, Alves-Martins et al [ 77 , 78 ] reported increased levels of basal cortisol related to high contents of arachidonic acid (ARA) in the diet of Senegalese sole larvae. However, when dietary FO is substituted by a blend of vegetable oils and a balanced n-3 to n-6 LC-PUFA ratio is provided in the diet, no differences are found with respect to diets based on FO and even some stress effects can be prevented [ 16 , 79 ].…”