Comparative fatty acid profiles of wild and farmed tropical freshwater fish rohu (Labeo rohita)

Effects of dietary arachidonic acid (ARA) on immunity, growth and fatty acids of Apostichopus japonicus

As an important aquaculture species, improving the immunity of cultured Apostichopus japonicus (A. japonicus) is vital for its health in aquaculture farming. It has been shown that ARA is an important metabolite for A. japonicus infected by Vibrio splendidus. In this study, we aimed to determine the effects of dietary exogenous ARA on healthy sea cucumber cultures, including assessments of immunity, growth, and fatty acid content. Five experimental diets containing 0.01%, 0.29%, 0.46%, 0.70%, and 1.09% ARA were tested. The specific growth rate (SGR) of sea cucumbers did not be significantly affected by exogenous ARA diet groups. The results showed that dietary ARA between 0.49 and 1.09% notably improved the survival rate of sea cucumbers infected by Vibrio splendidus compared with the control group without exogenous ARA. The results also showed the effects of dietary ARA on immune-related genes, enzymes, and oxidation indices; most of the exogenous ARA significantly upregulated the mRNA expression of the genes NFκB, TLR, TLR3, TRAF6, Toll, and MyD88. The activities of ACP, AKP, and lysozyme increased in the 0.49-1.09% ARA groups, especially the dietary 0.49% ARA group. The SOD1 and NOS activities were enhanced by dietary ARA between 0.29 and 0.70%. Compared with the control, the MDA content increased, but the 0.49% ARA-diet group had a lower MDA content. Based on these data, 0.49-0.70% ARA significantly enhanced immunity in cultured A. japonicus. Exogenous 0.49% and 0.70% ARA also elevated the ARA, total PUFA and n-6 PUFA in the body walls. In conclusion, the appropriate exogenous ARA (0.49%-0.70%) in diets could improve immunity and fatty acid content considerably. The results provide basic evidence that ARA can serve a useful immune enhancer for A. japonicus aquaculture.

Comparison of Fatty Acid Contents and MMP-1 Inhibitory Effects of the Two Antarctic Fish, Notothenia rossii and Champsocephalus gunnari

Total fatty-acid (FA) contents of different organs (stomach, liver, brain, and skin) of two Antarctic fish, marbled rockcod (Notothenia rossii) and mackerel icefish (Champsocephalus gunnari), were examined using gas chromatography–mass spectrometry (GC–MS). N. rossii possessed higher contents of total omega-3, where eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the most represented omega-3 FAs, were distributed throughout all parts of the fish. The highest level of EPA was observed in the skin and that of DHA was observed in the brain of N. rossii. C. gunnari showed organ peculiarity in that most of the omega-3 FAs were found in stomach and skin. Specifically, the highest levels of EPA and DHA were both observed in the stomach. Although N. rossii and C. gunnari both inhabit the Antarctic Southern Oceans, their characteristics in terms of the composition of fatty acids were shown to vary. The extracts were also evaluated for matrix metalloproteinase-1 (MMP-1)-inhibitory activities in UVB-induced human dermal fibroblasts, where extracts of the skin and liver of N. rossii showed the most significant inhibition upon MMP-1 production. These findings provide experimental evidence that the extracts of the Antarctic fish could be utilized as bioactive nutrients, particularly in the enhancement of skin health.

The dietary arachidonic acid improved growth and immunity of honey bee (Apis mellifera ligustica)

Honeybees cannot synthesize arachidonic acid (ARA) themselves, only obtain it from food. Most pollen is deficient or contains a small amount of ARA. The necessity of supplementary ARA in bees' diet has not been studied. The objective of this study was to investigate the effects of dietary ARA levels on the growth and immunity of Apis mellifera ligustica. A total of 25 honeybee colonies were randomly assigned to five dietary groups which were fed basic diets supplemented with 0, 2, 4, 6, and 8% of ARA. The diet with 4% ARA improved the body weight of newly emerged worker bees compared with the control group. Supplement of ARA in honeybee diets changed the fatty acid composition of honeybee body. SFA and MUFA contents of bees' body declined, and PUFA content rised in the ARA group. Compared with the control group, the supplement of ARA in honeybee diets increased the contents of ARA, C22:6n-3 (DHA) and C18:3n-6 in bees' body significantly, but decreased the contents of C16:1 and C18:3n-3. The diet supplied with 4% ARA reduced the mortality rate of honeybee infected with Escherichia coli. The activity of immune enzymes (phenoloxidase, antitrypsin, and lysozyme) and the mRNA expression levels of immune genes (defensin-2, toll, myd88, and dorsal) were improved by ARA diets to varying degrees depending on the ARA levels, especially 4% ARA. These results suggested that dietary ARA could improve the growth, survival, and immune functions of honeybees. Supplement of ARA in bees' diet would be valuable for the fitness of honeybees.

Characterization of Metabolite Compositions in Wild and Farmed Red Sea Bream ( Pagrus major) Using Mass Spectrometry Imaging

Nutritional profiles and consumer preferences differ between wild and farmed fish, and identification of fish sources can be difficult. We analyzed the metabolite molecules of wild and farmed red sea bream ( Pagrus major) to identify specific metabolic differences. The total lipid content and molecular composition of wild and farmed red sea bream muscles were analyzed using thin-layer chromatography and mass spectrometry imaging. Triacylglycerol levels were significantly higher in farmed fish. Wild fish contained saturated-fatty-acid-containing triacylglycerols as a major molecular species, while docosahexaenoic-acid-containing triacylglycerol levels were significantly higher in farmed fish than in wild fish. The localization of each muscle-fiber-type-specific marker demonstrated that wild fish exhibit myosin heavy chain (MHC)-type-IIb-specific phospholipids, while farmed fish exhibit MHC-type-IIa-specific phospholipids in their white muscle. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analyses separated the identified myosins and revealed that farmed fish possess additional myosin isoforms when compared to wild fish. In addition, we found a farmed-fish-specific distribution of anserine in their white muscle. These molecules can be used as new molecular markers for determining the geographic origins of wild versus farmed red sea bream.

Effects of Different Treatments on the Quality and Safety of Crayfish (Astacus leptodactylus)

This study was aimed to determine the effect of different killing methods (frozen, mechanical, and traditional) on the quality, safety, and shelf life of crayfish that are aerobically stored under chilled conditions. The population of microorganisms (i.e., total mesophilic aerobic bacteria (TMAB), total psychrophilic aerobic bacteria (TPAB), and Enterobacteriaceae) was increased regarding to storage time (p<0.05). Significant differences (p>0.05) were not observed in pH values during storage time. In contrast to this, total volatile basic nitrogen (TVB-N) values of the samples were increased significantly (p<0.05) during storage. Sensory results were highly correlated with the microbiological counts (r=-0.92 for TMAB × odour; r=-0.95 for TPAB × odour; and r=-0.96 for Enterobacteriaceae × odour). Fifteen different fatty acids and 5 biogenic amines were detected for the determination of initial quality and safety of crayfish. In conclusion, frozen killed samples were found to be effective and laborsaving method as an alternative to traditional killing methods by maintaining the quality and safety of crayfish at the beginning and during storage under chilled conditions.

The effect of dietary arachidonic acid (ARA) on growth performance, fatty acid composition and expression of ARA metabolism-related genes in larval half-smooth tongue sole (Cynoglossus semilaevis)

The present study was conducted to investigate the effects of dietary arachidonic acid (ARA) on growth performance, fatty acid composition and ARA metabolism-related gene expression in larval half-smooth tongue sole (Cynoglossus semilaevis). Larvae (35 d after hatching, 54 (sem 1) mg) were fed diets with graded concentrations of ARA (0·01, 0·39, 0·70, 1·07, 1·42 and 2·86 % dry weight) five times per d to apparent satiation for 30 d. Results showed that increased dietary ARA concentration caused a significant non-linear rise to a plateau in survival rate, final body weight and thermal growth coefficient, and the maximum values occurred with the 1·42 % ARA treatment. As dietary ARA increased to 1·07 or 1·42 %, activities of trypsin, leucine aminopeptidase and alkaline phosphatase levels increased, but they decreased with higher ARA concentrations. The fatty acid composition of tongue sole larvae was almost well correlated with their dietary fatty acid profiles, and the EPA content of the larvae decreased with increasing dietary ARA. Meanwhile, the partial sequences of COX-1a (cyclo-oxygenase-1a), COX-1b (cyclo-oxygenase-1b), COX-2 (cyclo-oxygenase-2), 5-LOX (5-lipoxygenase) and CYP2J6-like (cytochrome P450 2J6-like) were also obtained. Both COX-2 and 5-LOX mRNA expression levels significantly increased to a plateau in an ‘L’-shaped manner as dietary ARA increased to 1·07 or 1·42 %, but no significant differences were found in the gene expression of COX-1a, COX-1b or CYP2J6-like. These results suggest that 1·07–1·42 % dietary ARA was beneficial to the growth performance of larval tongue sole, and the regulation of dietary ARA on the growth performance of larvae was probably involved in altering the mRNA expression of COX-2 and 5-LOX.

Fatty Acid composition and levels of selected polyunsaturated Fatty acids in four commercial important freshwater fish species from lake victoria, Tanzania

Fatty acids (FAs) particularly ω3 and ω6 polyunsaturated fatty acids (PUFAs) play important role in human health. This study aimed to investigate the composition and levels of selected ω3 PUFAs in four commercial fish species, Nile perch (Lates niloticus), Nile tilapia (Oreochromis niloticus), Tilapia zillii, and dagaa (Rastrineobola argentea) from Mwanza Gulf in Lake Victoria. The results indicated that 36 types of FAs with different saturation levels were detected. These FAs were dominated by docosahexaenoic (DHA), eicosapentaenoic (EPA), docosapentaenoic (DPA), and eicosatetraenoic acids. O. niloticus had the highest composition of FAs (34) compared to L. niloticus (27), T. zillii (26), and R. argentea (21). The levels of EPA differed significantly among the four commercial fish species (F = 6.19,  P = 0.001). The highest EPA levels were found in R. argentea followed by L. niloticus and O. niloticus and the lowest in T. zillii. The DPA levels showed no significant difference among the four fish species studied (F = 0.652,  P = 0.583). The study concluded that all four commercial species collected from Mwanza Gulf are good for human health, but R. argentea is the best for consumption because it contains higher levels of ω3 FAs, mainly EPA.

Effect of heat treatment on the n-3/n-6 ratio and content of polyunsaturated fatty acids in fish tissues

The aim of this study was to compare the effect of different heat treatments (pan-frying, oven-baking, and grilling) on the contents of polyunsaturated fatty acids (PUFAs) in fish tissue. Four fish species were examined: pike, carp, cod, and herring. High performance liquid chromatography, coupled with electrospray ionization and mass spectrometric detection (HPLC/ESI/MS), was employed for determination of intact lipid molecules containing n-3 and n-6 PUFAs. Although mostly non-polar lipids (triacylglycerols, TGs) were present in the fish tissue, the PUFAs were present preferentially in the phospholipid fraction. Omnivorous fish species (carp, herring) contained more TGs than did predatory ones (pike, cod). Higher amounts of PUFAs were detected in the marine species than in the freshwater ones. The impact of heat treatments on the lipid composition in the fish tissue seems to be species-specific, as indicated by multivariate data analysis. Herring tissue is most heat-stable, and the mildest heat treatment for PUFA preservation was oven-baking.