Search

The aim of the present study was to evaluate the effects of Cu pre-exposure on antioxidant defense and energy metabolism in the liver of the large yellow croaker exposed to severe hypoxia. Fish were pre-acclimated to 0 and 30 μg Cu L−1 for 96 h, and subsequently exposed to 7.0 and 1.5 mg DO L−1 for another 24 h. Hypoxic stress alone increased reactive oxygen species and hepatic vacuoles. When compared to hypoxic stress alone, hypoxic stress plus Cu pre-exposure increased mortality and ROS production, and worsened histological structure by inhibiting antioxidant defense and aerobic metabolism, and enhancing anaerobic metabolism, suggesting Cu pre-acclimation aggravated hypoxia-induced oxidative damage. NFE2-related nuclear factor 2 and hypoxia-inducible factor-1α might participate in the transcriptional regulation of genes related to antioxidant response and energy metabolism, respectively. In conclusion, Cu pre-acclimation had a synergistic effect on antioxidant response and energy metabolism in fish under severe hypoxia, which contributes to understanding the molecular mechanisms underlying negative effects of Cu pre-acclimation against hypoxic damage in fish. Unlabelled Image • Hypoxia induced ROS and increased hepatic vacuoles. • Cu pre-exposure had a synergistic effect on hypoxia-induced oxidative damage. • Nrf2 mRNA level was paralleled with antioxidant gene expressions. • HIF-1α mRNA level was correlated with gene expressions of energy metabolism. [ABSTRACT FROM AUTHOR]

We studied the effects of dietary protein levels and water temperatures on growth performance, body composition, serum biochemistry, and digestive gland antioxidant enzyme activities of juvenile hybrid abalones Haliotis discus hannai♀ × H. fulgens♂ (1.47 ± 0.03 g ; 20.73 ± 0.16 mm). A 3 × 6 factorial design feeding trial was conducted with three water temperatures (19°C, 23°C, and 27°C) and six protein levels (152.5, 202.5, 252.6, 302.6, 352.7, and 402.7 g/kg) for 90 days. Dietary protein levels and temperature significantly affected the growth performance of the hybrid abalones, but there was no interaction effect except for daily increment in shell length. Body moisture decreased with increasing water temperature, and crude protein showed a contrary tendency. Crude lipid and ash were not affected by dietary protein level or water temperature. The alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase activities and the triglyceride content in serum increased with increasing water temperature, whereas the opposite was true for albumin activity and total protein and glucose contents. Total cholesterol contents decreased with increasing dietary protein levels. Dietary protein levels and water temperature did not affect contents of high-density lipoprotein cholesterol and low-density lipoprotein cholesterol (P > 0.05). A significant interaction was observed between dietary protein levels and water temperature in all antioxidation parameters (reactive oxygen species, total antioxidant capacity, protein carbonyl, superoxide dismutase, catalase, glutathione s-transferase, and glutathione peroxidase except for malondialdehyde content). Based on specific growth rate, the optimal dietary protein levels for juvenile hybrid abalones were 333.1, 318.6, and 306.3 g protein/kg diet at 19°C, 23°C, and 27°C, respectively. These findings will help to develop multidiet feeding strategies at different water temperatures throughout the culture period of juvenile hybrid abalones. [ABSTRACT FROM AUTHOR]

• Copper exposure induced oxidative damage and aberrant mitochondrial ultrastructure. • Pre-hypoxia exposure alleviated Cu-induced toxicological effects. • ROS were positively correlated with HIF-1α and FoxO3 gene expression. • MT protein levels were positively associated with Cu content. This study investigated the effects of moderate hypoxia pre-exposure on energy metabolism, antioxidant defence and mitophagy in the liver of the large yellow croaker Larimichthys crocea exposed to Cu. Fish were pre-exposed to either normoxia or hypoxia (~3.0 mg L−1, 42% O 2 saturation) for 48 h, and subsequently were subjected to either control (without Cu addition) or Cu (168 μg L−1) under normoxic conditions for another 48 h. Copper exposure under normoxia induced Cu toxicity that increased mortality, the production of reactive oxygen species (ROS) and malondialdehyde, and aberrant hepatic mitochondrial ultrastructure. Interestingly, hypoxia pre-exposure improved energy metabolism, antioxidant ability and mitophagy response, and reduced the Cu content to inhibit Cu toxicity, reflecting the enhanced survival rate and reduced oxidative damage. In these processes, hypoxia-inducible factor-1α (HIF-1α), transcription factors NFE2-related nuclear factor 2 (Nrf2), and forkhead box O-3 (FoxO3) mRNA levels were correlated with expression of genes related to energy metabolism, antioxidant defence and mitophagy, respectively, indicating HIF-1α , Nrf2 , and FoxO3 are required for the induction of their respective target genes. Overall, moderate hypoxia pre-exposure was able to generate adaptive responses to mitigate Cu-induced toxicological effects, underlining a central role of hormesis. [ABSTRACT FROM AUTHOR]

In commercial aquaculture, the phenomena of diet conversion and water temperature fluctuation commonly occur in abalone farming. The meat quality of abalone is affected by diet and temperature, and this in turn directly influences consumer acceptance of abalone products and financial returns to producers. The aim of this study was to investigate the impacts of diet (Gracilaria lemaneiformis vs artificial feed) and water temperature (low, 19 °C and high, 27 °C) on growth performance, nutritional value, flavor, and sensory quality of abalone. The results showed that artificial feed led to increases in growth, content of body protein, total free amino acids (TAA), delicious amino acids (DAA), volatile compounds (alcohols, acids, aromatic compounds, and esters), and sensory quality (hardness) of abalone meat. High temperature significantly decreased the growth, body moisture, n-3 polyunsaturated fatty acids, and hardness but increased the contents of DAA, TAA, alcohols, acids, and aromatic compounds in abalone meat. Our study suggests that high temperature significantly decreases the growth and nutritional value of abalone muscle but does provide a different mouthfeel and flavor for consumers, and nutrition-balanced artificial feed as the diet at a low water temperature maximizes the growth of abalone without sacrificing meat quality. The results may help to formulate an optimal feed strategy for farming industries throughout the abalone culture period, thereby allowing farmers to harvest premium quality abalone and elevate the market value of abalone products. • In commercial aquaculture, the phenomena of diet conversion and water temperature fluctuation commonly occur in abalone farming. • High temperature significantly decreases the growth and nutritional value of abalone muscle but does provide a different mouthfeel and flavor for consumers. • Artificial feed as the diet at a low water temperature maximizes the growth of abalone without sacrificing meat quality. [ABSTRACT FROM AUTHOR]

Two trials were conducted to determine the optimal replacement level of rice bran meal (RBM) as a substitute for kelp meal (KM) in the diet of the hybrid abalone Haliotis discus hannai ♀ × H. fulgens ♂. This study also investigated whether betaine as an attractant supplementation could be used to facilitate RBM as a replacement for KM. In Trial 1, RBM was used to replace 25%, 50%, and 100% of the dietary KM (RBM25, RBM50, and RBM100, respectively) based on a diet containing 30% KM (Con). In Trial 2, RBM50 was the same as in Trial 1, and betaine was supplemented in RBM50 at 0.2% (B1), 0.4% (B2), and 0.8% (B3) in the diets. Abalone (weight approximately 4 g) were randomly assigned to four groups replicated in triplicate (60 abalone/replicate). The abalone were fed the experimental diets for 10 weeks. In Trial 1, compared to the Con group, no significant differences were observed in final weight (FW), final shell length (FSL), specific growth rate (SGR), or daily increment in shell length (DISL) at 25% KM replacement by RBM. However, 50% KM replacement significantly reduced the FW, FSL, SGR, and DISL compared to the Con group. There were no significant differences in the proximate composition of the soft body tissues of the abalone. In Trial 2, growth performance parameters of the hybrid abalone were significantly improved with increasing levels of betaine in the diets compared to those fed diet RBM50, reaching the maximum value in the B2 group. Consistent with the feed intake results, the hormone concentrations of neuropeptide Y (NPY) and orexins in the digestive gland and cerebral ganglia of abalone were significantly increased when the supplementation level of betaine in the diets was increased to 0.2%. However, no apparent impacts were observed on NPY or orexin concentrations among the B1, B2, and B3 groups. Finally, we suggest 0.4% betaine supplementation along with replacing 50% of the KM with RBM in the hybrid abalone diet. The optimal diet is a cost-effective alternative feed formulation that can reduce the dependence on KM for abalone production in China. This study also demonstrates the potential of betaine as a feed attractant in abalone aquaculture. • 25% kelp meal (KM) can be replaced by rice bran meal (RBM) without obvious adverse impacts on the growth performance of the hybrid abalone. • The addition of 0.4% betaine in diets increased the replacement level of KM by RBM to 50% without negatively affecting the growth performance of the hybrid abalone. • Development of such diets will significantly reduce feed cost and reliance on KM for abalone feed company in China. [ABSTRACT FROM AUTHOR]

In this study, the optimal dietary protein levels for adult hybrid abalone (H. discus hannai♀ × H. fulgens♂) were evaluated at two representative temperatures, and the interactive influences of dietary protein and water temperature on abalone meat quality were examined. Six isoenergetic and isolipidic diets containing graded levels of protein (15%, 20%, 25%, 30%, 35%, and 40%) were fed to the hybrid abalone for 90 days. Based on the specific growth rate, the optimum dietary protein levels for adult hybrid abalone using a quadratic curve model were estimated to be 28.07% and 26.47% of the diet at 23 °C (optimum temperature) and 27 °C (high temperature), respectively. The amount of crude protein in the abalone body increased linearly with the dietary protein levels and water temperature. Antioxidation enzyme activities of abalone muscle, including GPx and GST were significantly affected by the interaction of dietary protein levels and water temperature. As for texture analysis, the abalone kept at 23 °C exhibited higher meat hardness than those fed the same diets at 27 °C. The n-3 PUFAs (particularly DHA and EPA) in abalone meat were significantly influenced by dietary protein levels, and the highest content was observed in the 30% dietary protein group. These levels were not affected by water temperature. In addition, higher dietary protein levels and water temperatures increased the total contents of free amino acids and flavor amino acids (Asp + Glu + Gly + Ala + Arg + Tau). The cooking loss of abalone meat was reduced with increased protein levels and was significantly lower in the 23 °C group, along with a higher meat postmortem pH value. The collagen fiber ratio and collagen content of abalone meat were higher in the 23 °C group. In summary, for multiple diet feeding strategies in practical production of abalone aquaculture, the balance between the seasonally specific feeds cost benefits and the abalone meat quality should be carefully evaluated. • The optimum dietary protein levels of adult hybrid abalone were estimated to be 28.07% and 26.47% of the diet by the quadratic curve model at 23 °C (optimum temperature) and 27 °C (high temperature), respectively. • Beyond 30% dietary protein, the growth performance declined, but relatively increased the nutritional, flavor quality, and hardness of abalone meat at both water temperatures. [ABSTRACT FROM AUTHOR]

Abstract: Sufficient lysis of soil or sediment microbes is a critical step for analyzing microbial community structures and for preparing metagenomic DNA libraries. The present study compared lysis methods for recovering archaeal, bacterial, actinomycete, and fungal DNAs from a mangrove sediment sample. PCR results showed that individual procedures using SDS, lysozyme, sonication, freeze–thaw, microwave, and vigorous shaking could extract archaeal or bacterial DNA but failed for actinomycetes or fungi cells. In comparison, an integrated lysis procedure using SDS, lysozyme, and vigorous shaking successfully obtained fungal DNA, and a combination of SDS, lysozyme, vigorous shaking, and microwave treatments recovered DNA from actinomycetes. Denaturing gradient gel electrophoresis (DGGE) results showed that although single lysis procedures can lyse bacterial DNA, all of them assessed the indigenous bacterial community structure with significant biases. The integrated lysis protocols described in the present study could be useful for extracting DNA from various types of sediments. [ABSTRACT FROM AUTHOR]

The effect of feeding three semi-purified diets containing different lipid sources (anchovy oil, soybean oil and pork lard) on fecundity, hatchability and egg fatty acid composition of Chinese mitten-handed crab (Eriocheir sinensis) broodstock was compared with a fresh clam diet in a 6-month feeding trial. Broodstock crabs fed the diet containing pork lard showed poor fecundity and low hatchability. Crabs fed the diet containing soybean oil showed improved fecundity; however, no significant improvement in hatchability was observed. Broodstock fed the diet containing anchovy oil showed the highest fecundity and egg hatchability. Eggs from broodstock fed anchovy oil as sole dietary lipid had a higher n-3 polyunsaturated fatty acid (PUFA) content (33.3%) compared with those of crabs fed diets with soybean oil (20.1%) and pork lard (16.3%) as lipid sources. The results indicate a close correlation between: (1) the 20:5n-3 content of the egg lipid and fecundity; (2) the 22:6n-3 content and hatchability; and (3) fecundity, hatchability and n-3/n-6 fatty acid ratio. The results also suggest that each of these n-3 HUFAs may play different and specific roles in crab reproduction and that either must be adequate in the broodstock diet. [Copyright &y& Elsevier]