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This study analyzed the differential gene expression in the muscle of Litopenaeus vannamei with different growth rates caused by dietary fish (FO) or canola oil (CO) in feed to expand the knowledge of how a low n-3 highly unsaturated fatty acids (HUFA) diet affects growth performance. As expected, after a 28-day feeding trial, juvenile L. vannamei fed FO showed significantly higher final weight, weight gain, and specific growth rate than those fed CO. Furthermore, the muscle tissue in FO shrimp showed higher levels of eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) compared to CO shrimp. Transcriptional sequencing analysis on the tail muscle identified 98 genes expressed differentially between both treatments, mainly expression on myosin and actin isoforms related to growth rates. Moreover, shrimp fed with FO presented upregulated genes related to higher metabolic activity associated with enhanced growth rate. Shrimp fed CO had downregulation of genes associated with energy metabolism, potentially related to lower energy demand for growth. These findings enhance the comprehension of the relationship among diet composition, gene expression, and shrimp growth under culture conditions. Furthermore, the determination of selected gene expression like those found in the present study could be a potential tool to identify a cause of low shrimp growth in farms caused by a deficient HUFA diet. [ABSTRACT FROM AUTHOR]

Lipids are essential in feeds for rearing marine fish. Inadequate handling and storage of feeds can cause lipid oxidation, increasing toxic compounds while decreasing the nutrition quality of feeds and negatively affecting both the physiology and rearing performance of fish. Here, the effect of increasing oxidized lipids intake was assessed on rearing performance and health of juvenile L. guttatus. Experimental feeds (EF) were manufactured with different levels of total peroxides (PV, 26–107 meqO2 × kg−1) and anisidine value (AV, 74–154). A total of 270 fish (18 fish by tank, three replicates by treatment) with an initial average weight of 6.5 ± 1 g were reared in 3 m3 tanks for 45 days. Survival and growth rate decreased with increasing PV and AV, particularly in fish fed with higher values of oxidized lipids. Viscerosomatic index was positively correlated with increase of oxidized lipids in EF, probably caused by increasing food retention into the gut. Glucose in plasma was inversely correlated with PV and AV in EF and together with the damage observed (i.e., inflammatory nodules, necrosis, and higher hepatosomatic index) suggests a decrease of liver metabolism. The increases of PV and AV on feeds were positively correlated with levels of triacylglycerides and total cholesterol in plasma, indicating an alteration in lipid metabolism. The total protein content in plasma and hematocrit was not different among treatments; in contrast, hemoglobin content decreased compared with control, suggesting an increase in the fragility of blood cells and oxygen transport capacity. Highly unsaturated fatty acid (HUFA) composition in the brain and liver was not different between treatments, but PV and AV were inversely correlated with docosahexaenoic acid (DHA) levels in neutral lipids and eicosapentaenoic acid (EPA) and arachidonic acid (ARA) levels in polar lipids in liver tissue, suggesting a specific demand to counteract cell damage caused by the accumulation of oxidized lipids. The content of HUFA in total lipids from muscle suggests this is an important storage tissue, whereas EPA level decreased with oxidized lipids in the diet. The results showed that increasing oxidized lipids on the diet compromise the health condition and rearing performance of juvenile rose snapper L. guttatus. [ABSTRACT FROM AUTHOR]

Juveniles fed a diet containing a low or a high level of highly unsaturated fatty acids (HUFA) for 38 days were exposed to handling stress. In a first experiment, stress was applied daily for 30 days, after which the physiological and immunological variables were measured, whereas in a second experiment, stress was applied once and samples were obtained 1 and 24 h after the stressor event. Shrimp that were stressed for 30 days showed significantly lower survival, final weight and feed consumption compared with unstressed shrimp. The concentration of the high-density lipoprotein β-glucan-binding protein was significantly higher in shrimp fed the high-HUFA diet. The glucose concentration in the haemolymph was significantly higher in long-term stressed shrimp compared to controls. The lactate level in the haemolymph was significantly lower in shrimp fed the high-HUFA diet. Lactate and glucose in the haemolymph increased in the 1-h stressed shrimp, but returned to normal levels in 24-h stressed shrimp. A negative effect of repeated-handling stress applied for 30 days was mainly observed on biological performance, whereas the single-stressor event had a more pronounced effect on shrimp physiological and immune responses measured 1 and 24 h after the stressor. A beneficial role of enrichment with HUFA on tolerance to handling stress was observed on immune response capacity. [ABSTRACT FROM AUTHOR]

Induction of triploidy in aquatic organisms has increased worldwide in the last two decades, mostly because triploids have better growth than diploids. According to a physiological hypothesis, partial or total sterility of triploids allows the accumulation of reserves in muscle and other tissues instead of being transferred to the gonad. The present study analyzes lipid, protein, carbohydrate, and fatty acid levels in muscle and gonads of Nodipecten subnodosus triploids and diploids over 18 months from June 2001 to December 2002. An important increase in gonadosomatic index of diploids scallops was observed from May to June 2002 reaching the highest values in August. Such increase was not observed in triploid scallops. Changes in biochemical composition in female gonad were in general related to the accumulation of reserves during gonad development of diploid scallops. This accumulation was lower for triploid scallops, in accordance to their sterility, especially for carbohydrates and acylglycerides. Adductor muscle index as well as protein and carbohydrate levels in muscle increased in both ploidy groups during the reproductive period indicating no mobilization of reserves to sustain gonad development in both ploidy groups. These results partially support the physiological hypothesis on the advantage of triploids: in a rich food locality no mobilization of reserves is needed to sustain gametogenesis. This, together with a possible lower efficiency of energy assimilation at high food concentration for triploids, may be the reason for an apparent lack of superiority of N. subnodosus triploids in terms of adductor muscle growth. Only the levels of particular highly unsaturated fatty acids levels (namely 20:4 n-6 and 20:5 n-3) in muscle of diploid and triploid decreased during the reproductive period, indicating a possible transfer of selected fatty acids to gonads, even in triploids. The muscle of triploids has a slightly but significantly higher proportion of 22:6 n-3 compared to diploids, which can have implications for the nutritional and commercial value of triploid adductor muscle. [ABSTRACT FROM AUTHOR]

Salinity stress tests are commonly applied in shrimp hatcheries to estimate the quality of postlarvae (PL) to be used during growout. Higher larval survival during culture and to a salinity stress test in both fish and crustaceans have been reported when specimens were offered a diet containing high levels of highly unsaturated fatty acids (HUFA). However, it is not clear if increased survival is a result of better overall physiological condition resulting from the diet or a specific effect of HUFA on osmoregulatory mechanisms. This study analyzed if HUFA-rich diets could modify the fatty acid composition of membranes in gills, and if this change in composition could affect the activity of the Na+/K+ ATPase pump and carbonic anhydrase in relation to changes in salinity. One-day-old postlarvae (PL1) pooled from different spawns were fed for 20 days with Artemia sp. nauplii enriched with three levels of HUFA: low, medium and high. At PL20, survivals during culture and to salinity stress test (tap water for 30 min) were evaluated. Also at this stage, Na+/K+-ATPase and carbonic anhydrase activity, morphometric variables, and fatty acid composition in the hepatopancreas and gills were measured after they were submitted to a salinity challenge in dilute seawater (10 ppt) for 3 h. No significant differences were observed in survival rates during culture, but survival to a salinity stress test was higher and gill area was larger in PL20 fed the Artemia sp. nauplii enriched with medium HUFA levels, probably as a result of an increased 22:6n-3 content and higher 22:6n-3/20:5n-3 ratio in this diet and in the tissues of the organisms fed this diet. Na+/K+-ATPase specific activity was significantly higher in posterior gills, while the specific activity of the carbonic anhydrase was higher in anterior gills. Enzymatic activities increased significantly in PL20 submitted to a salinity challenge, and HUFA levels in the diet affected both. The proportion of fatty acids in hepatopancreas and gills were significantly affected not only by diet, but also by exposure to dilute media. This effect is discussed in relation to an increase in gill surface and changes in fatty acid composition in the phospholipids present in gill membranes, which can modify the permeability and the activity of the Na+/K+-ATPase pump. The beneficial effect of HUFA supplementation in the diet on survival to salinity stress test is partially related to modification of fatty acid composition of gills and to a larger gill area, which in turn enhances osmoregulatory mechanisms, namely Na+/K+-ATPase and carbonic anhydrase activities. [Copyright &y& Elsevier]

Abstract: In a previous study, dietary supplementation with arachidonic acid (ARA) to oysters Crassostrea gigas increased haemocyte numbers, phagocytosis, and production of reactive oxygen species level (ROS) by haemocytes (). To assess if the observed stimulation of these cellular responses resulted from changes of ARA-related prostaglandin (PG) production, we analysed prostaglandin E2 metabolite (PGEM) content on the same oysters fed three levels of ARA. Dietary supply of polyunsaturated fatty acids (PUFA) could also induce an oxidative stress that could similarly increase cellular responses; therefore, two indicators of oxidative stress were analysed: peroxidation level and antioxidant defence status. Together the observed positive correlation between ARA and PGEM levels and the absence of lipid peroxidation and antioxidant activity changes supports the hypothesis of an immune stimulation via PG synthesis. Although ARA proportion in oyster tissues increased by up to 7-fold in response to ARA dietary supplementation, peroxidation index did not change because of a compensatory decrease in n-3 fatty acid proportion, mainly 22:6n-3. To further confirm the involvement of PG in the changes of haemocyte count, phagocytosis and ROS production upon ARA supplementation, it would be interesting to test cyclooxygenase and lipooxygenase inhibitors in similar experiments. [Copyright &y& Elsevier]

Marine by–products are rich in highly-unsaturated fatty acids (HUFA), but are not usually used as meal because they are composed by a non-homogeneous mix of tissues that are difficult to process and tend to decompose faster than muscle-based meals, like fish meal. They might also contain high levels of some heavy metals that are accumulated in the digestive gland/liver. Here we compared by–product meals as commonly produced by cooking (100 °C/10 min) that has the advantage of preserving meals for a longer shelf-life, against batch drying (60 °C/24 h) which should better preserve the HUFA and other labile lipids, in by–products (scallop viscera, squid viscera, shrimp heads) vs. whole fish (mackerel) as process control. Raw mackerel contained the highest crude protein (668 g/kg dw) while raw squid viscera had more lipids (200 g/kg), HUFA (40 g/kg), pigments (188 mg/kg), and cholesterol levels (26 g/kg), the last similar to levels in shrimp heads. Raw scallop viscera had the lowest content of protein (500 g/kg), lipids (75 g/kg), and cholesterol levels (6 g/kg), but presented the highest levels of different phytosterols, cadmium (303 mg/kg), and lead (16 mg/kg), with high levels of mercury comparable only to mackerel (302–365 μg/kg). Cooking significantly decreased protein to 474 g/kg and HUFA to 15 g/kg in mackerel, phospholipids were significantly reduced in all tested by-products, while triacylglycerides were reduced in almost all, except shrimp heads meal. Lead, cadmium and mercury were significantly reduced in cooked scallop viscera meal. Cooking increased peroxidation in scallop viscera and mackerel meal, but not in squid viscera or shrimp heads meal. Drying reduced cholesterol levels more than cooking, but only in squid viscera and shrimp heads meals. We conclude that cooking should be used in mercury-rich by-products, while drying is better when using scallop viscera or mackerel, particularly for using as alternative to discarding by-products and increasing fishery value. [ABSTRACT FROM AUTHOR]