Reparative effect of different dietary additives on soybean meal-induced intestinal injury in yellow drum (Nibea albiflora).

Soybean meal (SBM) is an acceptable replacement for unsustainable marine fish meal (FM) in aquaculture. However, we previously reported that high dietary SBM supplementation causes intestinal inflammatory injury in yellow drum (Nibea albiflora). Accordingly, a 4-week SBM-induced enteritis (SBMIE) in yellow drum trial was conducted first, followed by a 4-week additive-supplemented reparative experiment to evaluate the reparative effect of five additives on SBMIE in yellow drum. The control diet comprised 50% FM protein substituted with SBM. The additive-supplemented diet was added with 0.02% curcumin (SBMC), 0.05% berberine (SBM-BBR), 0.5% tea polyphenols (SBM-TPS), 1% taurine (SBM-TAU), or 0.8% glutamine (SBM-GLU) based on the control diet, respectively. The weight gain (WG), specific growth rate (SGR), feed efficiency ratio (FER), and survival rate (SR) of fish fed the additive-supplemented diets were significantly higher than those of fish fed the SBM diet. The WG, SGR, and FER of fish fed the SBMC, SBM-GLU and SBM-TAU diets were significantly higher than those of fish fed other diets. Moreover, fish fed the additive-supplemented diets SBMC and SBM-GLU, exhibited significantly increased intestinal villus height (IVH), intestinal muscular thickness (IMRT), and intestinal mucosal thickness (IMLT) and significantly decreased crypt depth (CD) in comparison with those fed the SBM diets. The relative expression of intestinal tight junction factors (ocln, zo1), cytoskeletal factors (f-actin, arp2/3), and anti-inflammatory cytokines (il10, tgfb) mRNA was remarkably elevated in fish fed additive-supplemented diets than those of fish fed the SBM diet. Whereas, the relative expression of intestinal myosin light chain kinase (mlck) and pro-inflammatory cytokines (il1, il6, tnfa) mRNA was markedly lower in fish fed the additive-supplemented diets. The highest relative expression of intestinal ocln, f-actin, and arp2/3 and the lowest relative expression of intestinal mlck were found in fish fed the SBMC diet. Hence, all five dietary additives effectively repaired the intestinal injury induced by SBM, with curcumin exhibiting the strongest repair effect for SBMIE in yellow drum.

A Comparative Study on Growth Performance, Body Composition, and Liver Tissue Metabolism Rearing on Soybean Lecithin-Enriched Artemia Nauplii and Microdiet in Rock Bream (Oplegnathus fasciatus) Larvae.

This study is aimed at establishing optimal soybean lecithin (SL) enrichment protocols in Artemia nauplii and at comparing the growth performance, body composition, and liver tissue metabolism in rock bream (Oplegnathus fasciatus) larvae reared on SL-enriched Artemia nauplii or SL-enriched microdiet (MD). The enrichment protocol experiment results indicated 12 h enrichment, and 10 g SL/m3 seawater could obtain desirable results. Rock bream larvae (25 days posthatching (dph)) were fed Artemia nauplii or MD for 30 days with three replicates. At stage 1 (larval 25-40 dph), significantly higher growth performance was observed in larvae fed the live prey (P < 0.05). Conversely, at stage 2 (41-55 dph), feeding with MD significantly increased larval standard length, and specific growth rate compared with those of larvae fed live prey. Larvae fed a MD showed decreased lipolysis-related lipase activity as well as decreased amino acid catabolism-related alanine aminotransferase and aspartate aminotransferase enzyme activities in liver tissue. RNA sequencing revealed that feeding with the MD primarily increased the expression of lipogenesis-related genes and protein translation-related gene expression in the liver tissue. Notably, feeding with MD significantly increased ribosome biogenesis-related genes as well as mitochondria synthesis-related gene expression, indicating a high protein anabolism rate and high energy production in liver tissue. In conclusion, 10 g SL/m3 seawater and 12 h could effectively enrich SL in Artemia nauplii. Retard weaning onto MD led to lower growth performance, which was likely due to the diversity of lipid and protein metabolism.

Comparative Transcriptome Analyses Characterize Expression Signatures Among Males, Females, Neo-Males, and Gynogenetic Females in the Yellow Drum (Nibea albiflora).

The yellow drum (Nibea albiflora) is one of the most important marine economic fish in China, and its sexually dimorphic growth makes it preferable for mono-sex culture. Although gynogenesis and neo-male induction techniques have been established, the molecular pathways and regulatory mechanisms of sex determination and maintenance in gynogenetic females and neo-males remains far from fully understood. In this study, the gene expression profiles were investigated in the gonads and brains of wild-type male, wild-type female, neo-male, and gynogenetic female yellow drum using comparative transcriptome analyses. Generally, a total of 52,999 novel transcripts were obtained in RNA-seq, of which 45,651 were isoforms of known protein-coding genes, 1,358 novel protein-coding genes, and 5,990 long non-coding RNAs. We found that the differences between wild-type males and neo-males and between wild-type females and gynogenetic females were relatively small at both the histological and transcriptomic levels, indicating that artificial gynogenesis or hormonal sex reversal may have minimal effects on normal female or male life function, respectively. In the brain, pathways such as "Oocyte meiosis", "Cell cycle", and "Riboflavin metabolism" were found to be significantly enriched. In the gonads, pathways such as "Prolactin signaling pathway", "PPAR signaling pathway", "Cholesterol metabolism", and "Jak-STAT signaling pathway" were found to play important roles in maintaining the regular proliferation and differentiation of females and males in yellow drum. In particular, we found that zp4 might be an effective molecular marker to differentiate between gynogenetic and normal females owing to its unique expression pattern. The results of this study may help to elucidate the molecular mechanisms involved in sex maintenance in the gonads and brain and provide basic data for genetic breeding of the yellow drum.

Chromosome-scale assembly and high-density genetic map of the yellow drum, Nibea albiflora.

The yellow drum (Nibea albiflora) is an economically important sciaenid fish in East Asian countries. In this study, we sequenced and assembled a near-complete gynogenetic yellow drum genome. We generated 45.63 Gb of Illumina short-reads and 80.27 Gb of PacBio long-reads and assembled them into a 628.01-Mb genome with a contig N50 of 4.42 Mb. Twenty-four chromosomes with a scaffold N50 of 26.73 Mb were obtained using the Hi-C analysis. We predicted a set of 27,069 protein-coding genes, of which 1,581 and 2,583 were expanded and contracted gene families, respectively. The most expanded genes were categorised into the protein binding, zinc-ion binding and ATP binding functional pathways. We built a high-density genetic linkage map that spanned 4,300.2 cM with 24 linkage groups and a resolution of 0.69 cM. The high-quality reference genome and annotated profiles that we produced will not only increase our understanding of the genetic architecture of economic traits in the yellow drum, but also help us explore the evolution and unique biological characteristics of sciaenid fishes.

iTRAQ-based quantitative phosphoproteomics provides insights into the metabolic and physiological responses of a carnivorous marine fish (Nibea albiflora) fed a linseed oil-rich diet.

The limited production of fish oil (FO) cannot meet the increasing demand of the aqua-feed industry. Accordingly, the replacement of FO with sustainable alternatives such as vegetable oils has become imperative. Linseed oil (LO), which has an abundance of α-linolenic acid (ALA), is a promising FO alternative. Nevertheless, high dietary LO inclusion generally causes abnormal hepatic lipid accumulation and growth retardation across carnivorous marine fish species. Previous studies have attempted to elucidate the mechanisms with regard to gene and protein levels; however, little is known about posttranslational modifications. In the present study, iTRAQ phosphoproteomics was conducted to investigate the metabolic and physiological responses of the yellow drum (Nibea albiflora) fed an LO-rich or FO-rich diet. Identification and analyses of differentially abundant phosphorylated proteins in hepatic tissue were conducted with parallel reaction monitoring (PRM) verification in reference to the genome sequences of the yellow drum. Among the specific peptides that passed the threshold, 203 hyperphosphorylated and 182 hypophosphorylated peptides were identified. Several functional categories and pathways were associated with these proteins that were mostly related to lipid, amino acid, and carbohydrate metabolism. In particular, the AMP-activated protein kinase (AMPK) pathway, mechanistic target of rapamycin (mTOR) pathway, and citrate (TCA) cycle are discussed. STATEMENT OF SIGNIFICANCE: Dietary LO caused abnormal hepatic lipid accumulation and retarded growth performance. The abnormal hepatic lipid accumulation in the fish fed the LO-rich diet might have arisen from AMPK signaling pathway-mediated de novo synthesis of fatty acids and the synthesis of phospholipids. An mTOR signaling pathway-mediated reduction in ribosome protein synthesis could have been a factor in the growth retardation. Changes in UPS and autophagy proteins phosphorylation and aminotransferase activity levels were related to the flux of amino acids into the TCA cycle for ATP production. The results of PRM were highly correlated with the phosphoproteomics results. These findings will contribute to a better understanding of the mechanisms of abnormal hepatic lipid accumulation and retarded growth performance in carnivorous marine fish fed linseed oil-rich diets.

Overwinter mortality in yellow drum (Nibea albiflora): Insights from growth and immune responses to cold and starvation stress.

The yellow drum (Nibea albiflora) is an economically important maricultured fish in China, but the aquaculture of this species has recently been limited by an increase in overwinter mortalities associated with cold and starvation stress due to global climate changes. To better understand the interaction between starvation and cold-stress-driven overwinter mortality, we investigated the effects of these stresses on the growth performance, liver lesions, and immune response of yellow drum fish. The fish were subjected to different cold treatments and under starvation stress. The experiment lasted 30 days and involved four experimental groups: a fed group and a fasted group maintained at 16 °C (control), and a fed group and a fasted group subjected to cold stress at 8 °C. We found that the growth of yellow drum was severely affected by cold temperatures and starvation. Throughout the experimental period, the body weights were significantly lower in the groups subjected to starvation and cold stress than in the control group. The liver cells showed irregular shapes and disorderly arrangements in the stress groups; indicating liver lesions. The gene expressions of antioxidant enzymes (copper, zinc superoxide dismutase, manganese superoxide dismutase, iron superoxide dismutase, and catalase) in the liver were lower in the groups subjected to starvation and cold stress than in the control groups. These results were basically consistent with the enzyme activities of superoxide dismutase and catalase tested in the livers. In addition, activities of immunomodulatory enzymes (alkaline phosphatase and acid phosphatase) were also inhibited in groups subjected to stress throughout the experiment period. These findings suggested that starvation and cold stress inhibited growth, depressed liver function, and suppressed the immune system of yellow drum, which likely would lead to physiological failure and increased susceptibility to infection. The present study offers insights into the physiological and immune response of yellow drum under cold and starvation stress. These insights not only provide baseline information from which effective strategies can be established and appropriate management decisions formulated, but can also be used to improve the overwinter survival of this important fish species in China.

Molecular Cloning, Characterization, and mRNA Expression of Hemocyanin Subunit in Oriental River Prawn Macrobrachium nipponense.

Hemocyanin is a copper-containing protein with immune function against disease. In this study, a hemocyanin subunit named MnHc-1 was cloned from Macrobrachium nipponense. The full-length cDNA of MnHc-1 was 2,163 bp with a 2,028-bp open reading frame (ORF) encoding a polypeptide of 675 amino acids. The MnHc-1 mRNA was expressed in the hepatopancreas, gill, hemocytes, intestine, ovary, and stomach, with the highest level in the hepatopancreas. In the infection trial, the MnHc-1 mRNA transcripts in the hemocytes were significantly downregulated at 3 h after injection of Aeromonas hydrophila and then upregulated at 6 h and 12 h, followed by a gradual recovery from 24 to 48 h. The MnHc-1 transcriptional expression in the hepatopancreas was measured after M. nipponense were fed seven diets with 2.8, 12.2, 20.9, 29.8, 43.1, 78.9, and 157.1 mg Cu kg-1 for 8 weeks, respectively. The level of MnHc-1 mRNA was significantly higher in the prawns fed 43.1-157.1 mg Cu kg-1 diet than in that fed 2.8-29.8 mg Cu kg-1 diet. This study indicated that the MnHc-1 expression can be affected by dietary copper and the hemocyanin may potentially participate in the antibacterial defense of M. nipponense.

Effect of dietary vitamin C on the growth performance and innate immunity of juvenile cobia (Rachycentron canadum).

This study was conducted to evaluate the effects of dietary vitamin C on growth performance, hematologic parameters and innate immune responses in juvenile cobia, Rachycentron canadum. Seven practical diets were formulated to contain 0.0 (as the basal diet), 13.6, 27.2, 54.4, 96.6, 193.4 and 386.5 mg ascorbic acid equivalent kg(-1) diet. Each diet was fed to triplicate groups of juvenile cobia with initial body weight of 5.5 g in 500-L cylindrical fiberglass tank. The results of 8 weeks feeding trial showed that typical vitamin C-deficient signs such as spinal deformation and body nigrescence were observed in the fish fed the basal diet. Fish fed the basal diet had significantly lower weight gain, specific growth rate (SGR), protein efficiency ratio (PER) and feed efficiency (FE) than those fed the diets supplemented with vitamin C, but no significant differences were observed among diets supplemented with vitamin C. However, survival rate was significantly affected by the dietary vitamin C levels, fish fed the basal diet had lower survival rate than those fed the diets supplemented with vitamin C. The ascorbic acid concentration in liver was correlated positively with the dietary vitamin C levels, however, the thiobarbituric acid reactive substances (TBARS) concentrations in liver was not significantly affected by the dietary vitamin C levels, although, fish fed the basal diet had the highest TBARS values among all treatments. The activities of serum lysozyme, superoxide dismutase (SOD), alkaline phophatase (AKP) and total immunoglobulin (Ig) were significantly influenced by the dietary vitamin C levels, fish fed the basal diet had lower lysozyme, SOD, AKP and total Ig than those fed diets supplemented with vitamin C. The serum glucose and triglyceride concentrations were significantly affected by the dietary vitamin C levels. Fish fed the basal diet had lower red blood cell and hemoglobin values than those fed the vitamin C supplemented diets. The challenge experiment with Vibrio harveyi showed that lower cumulative survival was in fish fed the unsupplemented diet, the cumulative survival were significantly increased with increase of the dietary ascorbic acid levels from 13.6 to 96.6 mg kg(-1), while the cumulative survival reached plateau when dietary ascorbic acid levels increased from 96.6 to 386.5 mg kg(-1). These results indicated that dietary vitamin C did significantly influence on growth performance and immune response of juvenile cobia.