Vitamin C Enhances Vitamin E Status and Reduces Oxidative Stress Indicators in Sea Bass Larvae Fed High DHA Microdiets

Docosahexaenoic acid (DHA) is an essential fatty acid necessary for many biochemical, cellular and physiological functions in fish. However, high dietary levels of DHA increase free radical injury in sea bass (Dicentrarchus labrax) larvae muscle, even when vitamin E (α-tocopherol, α-TOH) is increased. Therefore, the inclusion of other nutrients with complementary antioxidant functions, such as vitamin C (ascorbic acid, vitC), could further contribute to prevent these lesions. The objective of the present study was to determine the effect of vitC inclusion (3,600?mg/kg) in high DHA (5?% DW) and α-TOH (3,000?mg/kg) microdiets (diets 5/3,000 and 5/3,000?+?vitC) in comparison to a control diet (1?% DHA DW and 1,500?mg/kg of α-TOH; diet 1/1,500) on sea bass larvae growth, survival, whole body biochemical composition and thiobarbituric acid reactive substances (TBARS) content, muscle morphology, skeletal deformities and antioxidant enzymes, insulin-like growth factors (IGFs) and myosin expression (MyHC). Larvae fed diet 1/1,500 showed the best performance in terms of total length, incidence of muscular lesions and ossification degree. IGFs gene expression was elevated in 5/3,000 diet larvae, suggesting an increased muscle mitogenesis that was confirmed by the increase in the mRNA copies of MyHC. vitC effectively controlled oxidative damages in muscle, increased α-TOH larval contents and reduced TBARS content and the occurrence of skull deformities. The results of the present study showed the antioxidant synergism between vitamins E and C when high contents of DHA are included in sea bass larvae diets.     

Identification of fish species by 5S rRNA gene amplification

The 5S ribosomal RNA is a very suitable target for easy, rapid and inexpensive fish species identification due to its structure, consisting of a conserved region followed by a species-specific noncoding region called ‘nontranscribed spacer’. We have exploited this species-specificity in length and sequence to discriminate among fish species which can be subjected to substitution in the fish markets. After sequencing and alignment of the corresponding portions of the 5S rRNAs of different fish species, we have designed the primer pairs necessary for PCR amplification on the DNA traits which most diverged and a primer pair on conserved regions. Our results have shown the feasibility, simplicity and reliability of the proposed approach for the detection of mislabelling or fraudulent substitution of fish species.     

Applying transcriptomics to better understand the molecular mechanisms underlying fish filet quality

Microfluidic capillary electrophoresis and real-time PCR were successfully applied to investigate the postmortem alterations in RNA extracted from fish muscular tissue in relation to three parameters: slaughtering method, time, and storage temperature.