WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2013 63 of stress (Betancor et al. 2011). However, at DHA levels up to 5 percent, the increase in vitamin E is not sufficient to counteract the ROS effect, with an increased incidence of muscular lesions, TBARS (an indicator of oxidative stress) and AOE gene expression (Betancor et al. 2012a, b, Bentancor et al. 2013a). In this case, vitamin E acts as a prooxidant, as a result of the oxidation of the vitamin E and the lack of regeneration, which, in turn, can initiate lipid peroxidation. Thus, if 5 percent DHA is included in larval microdiets, a great generation of ROS occurs, with vitamin E incapable of neutralizing them. Additionally vitamin E is not adequately regenerated and vitamin E-derived radicals continue the chain reaction of in vivo lipid peroxidation, with vitamin E acting as a prooxidant. Therefore, vitamin E is an effective antioxidant, but other antioxidant nutrients may be necessary to counteract ROS when dietary DHA levels in larval feeds are 5 percent. (CONTINUED ON PAGE 62) Interrelations Among Antioxidant Nutrients It is widely recognized that vitamin C and selenium have complementary and/or synergistic functions with vitamin E. In studies performed in our laboratory, increases in selenium and vitamin C increased larval growth and reduced muscular lesions and TBARS contents compared to larvae fed an nonsupplemented diet. Nonetheless, differences were observed in AOE expression, suggesting that both antioxidant nutrients act at different levels. Selenium reduced mRNA copy numbers of SOD and GPX to levels comparable to the control group fed with low DHA (1 percent) and vitamin E (1500 mg/kg), whereas vitamin C had no effect on the expression of any AOE. An interesting role of vitamin C as an antioxidant is the regeneration of oxidized vitamin E, which is observed TABLE 1. DHA requirements for fish larvae of different marine species (percent dry weight in rotifers Artemia or microdiets). Species Tested parameter Requirement Reference Acanthochromys poliacanthus GrowthSurvival 0.5 Southgate and Kavanagh 1999 Calotomus japonicus Growth 1-2 Kanazawa 1993 Centropomus parallelus Growth >0.6 Seiffert et al. 2001 Survival Swim bladder inflation Dentex dentex Growth 2.4 Mourente et al. 1999a Survival Hippoglossus hippoglossus Pigmentation 2.5 Hamre and Harboe 2008 Eye migration Latris lineata Growth 1.3 Brandsen et al. 2004 Survival Behaviour Pagrus major Growth 0.95-1.62 Furuita et al. 1996a Survival Salinity tolerance Growth 1.5 Rotifers or Artemia Izquierdo et al. 1990 Survival Pagrus pagrus Growth 1.5 Hernández-Cruz et al. 1999 Survival Paralychthis olivaceous Growth 1 Kanazawa 1995 Psetta maxima Growth 0.8 Reitan et al. 1994 Pseudocaranx dentex Growth 1.6-2.2 Takeuchi et al. 1996 Pseudopleuronectes herzensteini Growth 0.6 Rotifers Satoh and Takeuchi Survival 1.4-2.8 Artemia 2009 Starvation resistance Larval development Sparus aurata Growth >3 Izquierdo 2005 Survival Scophtalmus maximus Growth 3.2 Le Milinaire 1984 Seriola dumerilii Growth 4 Izquierdo 2005 Survival
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