In order to enhance growth, survival and quality during early juvenile stages of marine fish it is important to avoid lipid oxidation problems that are known to cause pathologies and disease. The aim of the present study was to characterise and compare the antioxidant systems in juvenile marine fish of commercial importance in European aquaculture, namely turbot (Scophthalmus maximus), halibut (Hippoglossus hippoglossus) and gilthead sea bream (Sparus aurata). The experiment investigated the interaction of the dietary antioxidant micronutrient, vitamin E, with antioxidant defence systems. Fish were fed diets of identical unsaturation index supplemented with graded amounts of vitamin E. The relationships between dietary and subsequent tissue vitamin E levels were determined as well as the effects of vitamin E supplementation on lipid and fatty acid compositions of both liver and whole fish, on the activities of the liver antioxidant defence enzymes, and on the levels of liver and whole body lipid peroxidation products, malondialdehyde (thiobarbituric acid reactive substances, TBARS) and isoprostanes. Growth and survival was only significantly affected in sea bream where feeding the diet with the lowest vitamin E resulted in decreased survival and growth. A gradation was observed in tissue vitamin E and PUFA/vitamin E levels in response to dietary vitamin E levels in all species. The activities of the main radical scavenging enzymes in the liver, catalase, superoxide dismutase and glutathione peroxidase generally reflected dietary and tissue vitamin E levels being highest in fish fed the lowest level of vitamin E. The indicators of lipid peroxidation gave consistent results in all three species, generally being highest in fish fed the unsupplemented diet and generally lowest in fish fed the diet with highest vitamin E. In this respect, isoprostane levels generally paralleled TBARS levels supporting their value as indicators of oxidative stress in fish. Overall the relationships observed were logical in that decreased dietary vitamin E led to decreased levels of tissue vitamin E, and generally higher activities of the liver antioxidant enzymes and higher levels of lipid peroxides

The overall aim is the characterization of the antioxidant systems in marine fish during early development in order to enhance growth and quality of early life stages by avoiding oxidation problems that may cause pathologies and disease. The present study determined the activities of the antioxidant system enzymes and levels of vitamin E, lipid peroxidation products and fatty acids during early development without exogenous feeding in the marine fish, Dentex dentex. Samples of fertilized eggs just prior to hatch, newly hatched larvae and unfed larvae up to day 9 after hatch were analysed on a daily basis.The larvae did not grow during the experiment and by day 9 the surviving larvae weighed only a third of the newly hatched larvae. Lipid was a major energy source during this period of starvation as evidenced by greatly decreased amounts of total lipid due to a preferential utilisation of neutral lipids. All groups of fatty acids (saturated, monounsaturated and polyunsaturated) were consumed throughout the starvation period. Vitamin E levels were relatively constant until significantly declining by days 8 and 9. Similarly, levels of lipid-soluble fluorescent products (LSFP) were relatively constant until day 6 and then significantly decreased from days 7 to 9. In contrast, the level of malondialdehyde (MDA) was very high in eggs but was 3-fold lower in newly hatched larvae and then decreased over the whole time-course and was also significantly lower on days 8 and 9.The activities of enzymes of the antioxidation system were expressed in both eggs and early larvae and varied during the developmental period with levels of catalase and glutathione peroxidase (GPX) being initially low in eggs whereas glutathione-Stransferase (GST) and superoxide dismutase (SOD) were higher in eggs than in larvae.Overall, the activities of catalase and GPX increased, whereas GST and total SOD activities decreased, during the early stages of development during a period where there was no exogenous dietary input into the larvae. Glutathione reductase activity was very low and showed an increasing trend initially until days 2-3 before declining and varying over the remaining period.In conclusion, we determined the prooxidant (polyunsaturated fatty acid) status, antioxidant status (vitamin E), peroxidation status (MDA and LSFP) and the activities of the antioxidant enzyme systems in a single integrated study in unfed marine fish larvae during early development.

Selection of new autochthon strains is necessary, and for the moment the best strategy, to find microalgae well adapted to the local climatological conditions able to simultaneously produce several compounds of biotechnological interest and grow at high rates. We describe the isolation and characterization of a new microalgal strain isolated from the marshlands of the Odiel River in the Southwest of Spain. The new microalga belongs to the genus Picochlorum, as deduced from the analysis of its 18S rRNA encoding gene, is able to grow at a high growth rate and thrive with adverse conditions. It has an appreciable constitutive level of lutein (3.5 mg g(-1) DW) and zeaxanthin (0.4 mg g(-1) DW) which is increased to 1.8 mg g(-1) DW at high light intensities. This strain is also characterized by a very low level of linolenic acid (3.8% of total fatty acids) and no polyunsaturated fatty acids with four or more double bonds. Although the total lipid content is not particularly high, 23% of the dry weight, its fatty acid profile makes of Picochlorum sp HM1 a promising candidate for biodiesel production, and the high content in the carotenoids lutein and zeaxanthin indicates that the microalga could also be a good source for natural eye vitamin supplements, which could be obtained as co-products.

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Growth and condition of larval Engraulis encrasicolus larvae in the Bay of Biscay were analysed relative to their biochemical composition. Protein, carbohydrate, lipid, DNA and RNA contents of larvae were quantified during larval ontogeny to analyse changes associated with growth. Proteins were the main organic component of E. encrasicolus at every larval stage, followed by lipids and carbohydrates. The increase in relative protein content in terms of protein percentage (P%) and the decrease in lipid relative content (L%) of the total organic matter (OM) with size observed are consistent with the definition of Type 1 larvae. Protein relative content increased until the P% in larvae reached ~71%, whereas L% and carbohydrate relative content (CH%) declined, exhibiting minimum values of ~20, and ~6%, respectively. In general terms, the feeding condition of larvae, as defined by their RNA/DNA ratio, was good. Food did not seem to be a major factor limiting larval growth in the study area throughout late spring and early summer. The RNA/DNA ratio was size-related and increased during larval growth up to an asymptotic optimal value of ~3.6 in postflexion larvae in relative protein content, in terms of protein percentage (P%). The 'actual' RNA/DNA ratios found in a given larval population when compared with the 'starving' RNA/DNA ratio, and using an 'absolutely optimal' value as complementary information, could be used to determine the overall status of the population. Parental effect of low egg quality is a possible explanation of delayed ontogenetical development of larvae from July 2000.