Effects of Chronic Stress from High Stocking Density in Mariculture: Evaluations of Growth Performance and Lipid Metabolism of Rainbow Trout (Oncorhychus mykiss).

(1) Background: In aquaculture, chronic stress due to high stocking density impairs animals' welfare and results in declined fishery production with low protein quality. However, most previous studies evaluated the effects of high stocking density on trout in freshwater rather than seawater. (2) Methods: Juvenile trout were reared for 84 days in circular tanks under three stocking densities, including low density ("LD", 9.15 kg/m3), moderate density ("MD", 13.65 kg/m3), and high density ("HD", 27.31 kg/m3) in seawater. The final densities of LD, MD, and HD were 22.00, 32.05 and 52.24 kg/m3, respectively. Growth performance and lipid metabolism were evaluated. (3) Results: Growth performance and feeding efficiency were significantly reduced due to chronic stress under high density in mariculture. The digestive activity of lipids was promoted in the gut of HD fish, while the concentration of triglycerides was decreased in the blood. Furthermore, decreased acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), increased hormone-sensitive lipase (HSL) concentrations, and activated hepatic ß-oxidation processes were observed in trout under HD. Redundancy analysis showed that glycerol and HSL can be used as potential markers to evaluate the growth performance of trout in mariculture. (4) Conclusions: We showed that chronic high stocking density led to negative effects on growth performance, reduced de novo synthesis of fatty acids, and enhanced lipolysis.

Comparative Study of the Morphological Characteristics of Perforators of the Transverse and Descending Branches of the Lateral Circumflex Femoral Artery in Anterolateral Thigh Flap Surgery.

BACKGROUND: The anterolateral thigh flap (ALTF) is a kind of lateral thigh flap that uses branches of the lateral circumflex femoral artery (LCFA) as the vessel pedicle and is widely used in plastic surgery. During classic ALTF surgery, some perforators from the descending branch of the lateral circumflex femoral artery (LCFA-db) are hard to harvest due to their anatomical variants and individual differences; thus, it is necessary to design an appropriate alternative surgical plan. The transverse branch of the LCFA (LCFA-tb) has unique advantages and can be a potential complement to ALTF vascular pedicle selection. The aim of this study was to compare the difference in morphology between LCFA-db and LCFA-tb, and to verify the feasibility and clinical effect of ALTF with LCFA-tb as the source artery. METHODS: The morphological and clinical data of patients who underwent wound repair of the extremities with the ALTF pedicled with the LCFA-tb and LCFA-db were retrospectively analyzed. This study consisted of the clinical data of 62 patients who accepted an ALTF pedicled with LCFA-tb, and 45 patients accepted an ALTF pedicled with LCFA-db. RESULTS: A total of 68 cutaneous perforators originating from the LCFA-tb were found in the surgical field, of which 35 perforators were direct cutaneous perforators (51.5%), 28 perforators were septocutaneous perforators (41.2%), and 5 perforators were musculocutaneous perforators (7.3%). Seventy-four cutaneous perforators were found in the LCFA-db group. The proportions of septocutaneous perforators and musculocutaneous perforators were 23% and 77%, respectively, and the number of direct cutaneous perforators was 0. The harvest time of flaps pedicled with LCFA-tb was remarkably shortened. Regarding prognosis, there were no significant differences between the curative effects of the 2 types of flaps. CONCLUSIONS: This study verified that most LCFA-tb perforators are direct cutaneous perforators and that the piercing-in positions of LCFA-tb perforators on superficial fascia were higher than those of LCFA-db perforators. Furthermore, the ALTF pedicled with LCFA-tb can provide satisfactory soft tissue reconstruction and can be used as a useful supplement to the traditional flap design.

Alternative splicing patterns of hnrnp genes in gill tissues of rainbow trout (Oncorhynchus mykiss) during salinity changes.

Alternative splicing (AS) plays an important role in various physiological processes in eukaryotes, such as the stress response. However, patterns of AS events remain largely unexplored during salinity acclimation in fishes. In this study, we conducted AS analysis using RNA-seq datasets to explore splicing patterns in the gill tissues of rainbow trout exposed to altered salinity environments, ranging from 0 ‰ (T0) to 30 ‰ (T30). The results revealed 1441, 351, 483, 1051 and 1049 differentially alternatively spliced (DAS) events in 5 pairwise comparisons, including T6 vs. T0, T12 vs. T0, T18 vs. T0, T24 vs. T0, and T30 vs. T0, respectively. These DAS events were derived from 1290, 328, 444, 963 and 948 genes. Enrichment analysis indicated that these DAS genes were related to RNA splicing and processing. Among these, 14 DAS genes were identified as members of the large heterogeneous nuclear RNP (hnRNP) gene family. Alternative 3' splice site (A3SS), exon skipping (SE) and intron retention (RI) events resulted in the fragmentation or even loss of the functional RNA recognition motif (RRM) domains in hnrnpa0, hnrnp1a, hnrnp1b and hnrnpc genes. The incomplete RRM domains would hinder the interactions between hnRNP genes and pre-mRNAs. It would in turn influence the splicing patterns and mRNA stability of downstream target genes in response to salinity changes. The study provides insights into salinity acclimation in gill tissues of rainbow trout and serves as a significant reference on the osmoregulation mechanisms at post-transcription regulation levels in fish.

Effects of Dietary Zinc on Growth Performance, Digestive Enzyme Activities, Antioxidant Status, and Immune Responses of Sea Cucumber Apostichopus japonicus.

Zinc is an essential micronutrient for organisms involved in regulating various biological processes. This study evaluated the effects of dietary zinc on growth performance, digestive enzyme activities, antioxidant status, and immune responses of sea cucumber Apostichopus japonicus. Five experimental diets were formulated with graded levels of zinc (0, 20, 40, 60, and 80 mg/kg, respectively), and the actual dietary zinc values were 31.4, 51.0, 68.2, 91.9, and 110.8 mg/kg diet, respectively. Sea cucumbers were fed with diets for 2 months. The results showed the growth performance, amylase, and trypsin activities of sea cucumber increased significantly with zinc supplementation, and the best growth performance and enzyme activities were observed at 40 mg/kg zinc diet. Zinc supplementation significantly increased activities of superoxide dismutase, catalase, anti-superoxide anion, and inhibiting hydroxyl radical, while significantly reduced the malondialdehyde content. Furthermore, the higher zinc supplementation levels resulted in significantly upregulated immune-related genes of hsp90, p105, rel, and lsz, suggesting that excessive zinc caused oxidative stress. The broken-line regression analysis of specific growth rate indicated dietary zinc requirement in juvenile sea cucumber was ~ 66.3 mg/kg diet. Overall, dietary zinc contributes to the growth and immune resistance of juvenile sea cucumber, and our study will provide insights into the rational use of dietary zinc in aquaculture.

Co-exposure of nanoplastics and arsenic causes neurotoxicity in zebrafish (Danio rerio) through disrupting homeostasis of microbiota-intestine-brain axis.

Nanoplastics (NPs) and arsenic (As) are toxic pollutants prevalent on the earth and have gained considerable attention in recent decades. Although numerous studies reported NPs and As can cause neurotoxicity there are still significant knowledge gaps in illustrating their combined toxicity and its mechanism. In this study, the co-exposure of environmentally relevant concentrations of NPs and As caused neurobehavioral toxicity in zebrafish, as evidenced by reduced swimming ability, anxiety and impaired short-term learning memory. Potentially, its toxicity mechanism is through disrupting the homeostasis of microbiota-intestine-brain axis in zebrafish. Specifically, the co-exposure reduced the 5-hydroxytryptamine (5-HT) production in intestine, which led to lower levels of 5-HT transported by the blood circulation to the brain. Ultimately, neurobehavior was adversely affected by the reduced binding of 5-HT to its receptors. Intestine, the primary source of 5-HT, its impaired health (aggravation in oxidative stress, mitochondrial damage and histopathological alterations) induced the dysregulation in the 5-HT system, which may be induced by the increased accumulation of As in the intestine by the co-exposure. Besides, the reduced 5-HT levels were correlated with decreased Firmicutes and Protecbacteria and increased Actinobacteriota and Chloroflexi in intestines. Potentially, intestinal microbiota adversely regulates the intestine-brain axis by reducing SCFAs levels. Thus, the alteration of intestinal microbiota structure may be the other reason for the dysregulation of intestine-brain axis. In summary, co-exposure of NPs and As induced neurobehavior toxicity probably through disrupting the homeostasis of microbiota-intestine-brain axis. This study provides insights into assessing the environmental health risks of the pollution of NPs and As to aquatic organisms.

Temperature acclimation improves high temperature tolerance of rainbow trout (Oncorhynchus mykiss) by improving mitochondrial quality and inhibiting apoptosis in liver.

Global warming is threatening the survival and growth of cold-water fish, and the methods to improve the high-temperature adaptability of cold-water fish need to be explored urgently. This study aims to explore the mechanism of improving high temperature tolerance of rainbow trout by temperature acclimation (TA). Rainbow trout were acclimated by two modes at 22 °C, including fluctuating TA (FA) and constant TA (CA), and thereafter subjected to heat stress (HS) at 25 °C. Results showed that TA markedly increased the critical temperature maximum (CTmax) of rainbow trout. Secondly, the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in serum and malondialdehyde (MDA) in liver of CA + HS group significantly decreased compared to those in HS group without TA, indicating the reduction of liver injury by CA. Moreover, HS significantly induced ROS production and reduced mitochondrial membrane potential (MMP) in rainbow trout liver, but TA reduced the levels of ROS and increased the MMP in liver of rainbow trout after HS, indicating the reduced oxidative stress and mitochondrial damage. Furthermore, TA up-regulated the expression of genes related to mitochondrial autophagy, fusion, fission and biogenesis, as well as the expression of marker proteins of autophagy (LC3II) and mitophagy (Parkin) in the liver, so as to maintain mitochondrial homeostasis. Moreover, TA also inhibited the occurrence of apoptosis (decrease in bax/bcl-2), which may be owing to the reduced ROS and mitochondrial damage by TA. Interestingly, CA significantly up-regulated the genes expression of methyltransferase in the liver, which may inhibit the genes or transcription factors related to oxidative stress and apoptosis by DNA methylation. In conclusion, TA increased the upper limit of heat tolerance of rainbow trout by improving mitochondrial quality and inhibiting apoptosis in liver. This study will provide an effective solution to the risk of high temperature in cold-water fish culture.

Free amino acids in response to salinity changes in fishes: relationships to osmoregulation.

Free amino acids (FAAs) are believed to play important roles in osmoregulation and buffer capacity in some aquatic animals, such as fishes. However, the potential roles of FAAs have not been systematically summarized and characterized until now. In the present study, the meta-analysis was conducted to investigate the relationships between FAAs and environmental salinities. Twenty published documents were included, accounting for 106 study cases. The effect sizes of total free amino acids (TFAAs), total essential amino acids (TEAAs), and total non-essential amino acids (TNEAAs) to salinity increase were calculated and determined by the restricted maximum likelihood (REML) method. It clearly showed that the elevated salinities significantly induced the contents of TFAAs, TEAAs, and TNEAAs at the ratio of 36%, 27%, and 29%, respectively. Faced to the salinity changes, the contents of FAAs in fishes under freshwater and seawater varied significantly, while the individuals under brackish water displayed relatively constant contents of FAAs. When salinity elevated, the contents of 17 amino acids in muscles significantly increased, suggesting the important roles of FAA metabolism in osmoregulation in fishes. The results also indicated that the effect sizes of TFAAs were positively related to the rates of salinity increases, and exhibited a significant quadratic linear relationship with temperatures. Additionally, the contents of FAAs also showed positive correlation with osmotic pressure, concentrations of plasma Na+, Cl-, and urea, implying their potential roles of FAAs in osmoregulation in fishes. These findings suggested that elevated salinities greatly induced the contents of FAAs in fishes, making a great contribution to maintaining the homeostasis of fishes in response to environmental salinity changes.

Reconstruction of large-area wounds in limbs using two flow-through anterolateral thigh perforator flaps.

INTRODUCTION: Limb salvage in large wounds is difficult because the disrupted blood supply does not support a flap. This study evaluated the clinical efficacy of using two flow-through anterolateral thigh perforator flaps for reconstructing large-area limb wounds. METHODS: This retrospective study included 45 patients who underwent reconstruction of large limb wounds using two flow-through anterolateral thigh perforator flaps at Ruihua Hospital between January 2015 and December 2020. Wound areas ranged from 15 cm × 13 cm to 46 cm × 18 cm. Single flap areas ranged from 16 cm × 8 cm to 46 cm × 9 cm. Blood supply locations were identified using color Doppler ultrasound or digital subtraction angiography (DSA) images. Primary outcomes were flap survival and complications at recipient or donor sites during at least 6-months follow-up. RESULTS: The overall flap survival rate was 97% (87/90). All donor sites healed by first intention. Three cases developed vascular crises, which were alleviated by reoperation. One case had flexor contracture in left toes, relieved by cutting flexor tendons; 13 cases had flap bloat, relieved by flap thinning at 6 months. All cases showed properly healed wounds and functional reconstruction. CONCLUSIONS: Reconstruction of large-area limb wounds using two flow-through anterolateral thigh perforator flaps provides safe and satisfactory effects without donor-site morbidity, and with proper healing and restored function.

Identification, characterization, and transcription of serotonin receptors in rainbow trout (Oncorhynchus mykiss) in response to bacterial infection and salinity changes.

Serotonergic system is involved in the regulation of physiological functions and behavioral traits including cognition, memory, aggression, stress coping, appetite and immunomodulation. Serotonin exerts its functions via binding distinct serotonin receptors which are classified into 7 groups. Salmonid exhibits expanded functional gene copies due to salmonid-specific whole genome duplication. However, serotonin receptor (htr) repertoire is not fully identified in rainbow trout (Oncorhynchus mykiss). In this study, we identified 39 htr genes, including 14 htr1, 4 htr2, 4 htr2 like, 3 htr3, 4 htr4, 2 htr5, 2 htr6, and 6 htr7 subtypes. We investigated physiological functions of serotonin receptors in response to bacterial pathogens exposure and salinity changes. We showed htr1, htr2, htr4 and htr7 subtypes were associated with immunomodulation in response to Vibrio anguillarum or Aeromonas salmonicida infection. Saltwater (salinity of 15) transfer significantly altered htr1, htr2, htr4, and htr7 subtypes, suggesting trout Htr was associated with osmoregulation. We further showed residues interacted with inverse agonist (methiothepin) and serotonin analogue (5-Carboxamidotryptamine) were conserved between trout and human, suggesting exogenous ligands targeting human HTRs might have a role in aquaculture. This study showed duplicated trout Htrs might be physiologically neofunctionalized and potentially exhibit pleiotropic effects in regulating immunomodulation and osmoregulation.

Is the oblique branch of the lateral circumflex femoral artery a common variant?

The oblique branch of the lateral circumflex femoral artery, a short branch of the deep femoral artery, is highly prevalent (32-46%) and is usually considered a normal variant, although this is still controversial. This study aimed to evaluate whether the oblique branch of the lateral circumflex femoral artery is a variant. We reviewed medical record data of patients with skin and soft tissue defects of the extremities who underwent flap repair using free anterolateral thigh (ALT) flaps at our hospital in 2019. The anatomical characteristics of the flaps were examined intraoperatively by high-frequency color Doppler ultrasound. A total of 153 ALT flaps from 146 patients were included. Among the branches, 232 (73.7%) were oblique branches, and 83 (26.4%) were descending branches. Of the 232 oblique branches, 141 (60.8%) were from septocutaneous branches, and the other 83 (39.2%) were from musculocutaneous branches. In addition, 20 (24.1%) descending branches were from septocutaneous branches, and the other 63 (75.9%) were from musculocutaneous branches. Analyzing the prevalence of the oblique branch in septocutaneous branches, more than half of the patients had oblique branches rather than descending branches. The high proportion of oblique branches from septocutaneous branches (median: 100 (0-100) vs. 0 (0-50), p = 0.002) supports the understanding that the oblique branch is a normal anatomical element rather than a variant. The main type was the intramuscular branches, which required significantly less time for flap harvesting. The oblique branch may be the preferred vascular pedicle for free ALT flaps.

Comprehensive Analysis of YTH Domain-Containing Genes, Encoding m6A Reader and Their Response to Temperature Stresses and Yersinia ruckeri Infection in Rainbow Trout (Oncorhynchus mykiss).

YTH domain-containing genes are important readers of N6-methyladenosine (m6A) modifications with ability to directly affect the fates of distinct RNAs in organisms. Despite their importance, little is known about YTH domain-containing genes in teleosts until now. In the present study, a total of 10 YTH domain-containing genes have been systematically identified and functionally characterized in rainbow trout (Oncorhynchus mykiss). According to the phylogenetic tree, gene structure and syntenic analysis, these YTH domain-containing genes could be classified into three evolutionary subclades, including YTHDF, YTHDC1 and YTHDC2. Of them, the copy number of OmDF1, OmDF2, OmDF3, and OmDC1 were duplicated or even triplicated in rainbow trout due to the salmonid-specific whole-genome duplication event. The three-dimensional protein structure analysis revealed that there were similar structures and the same amino acid residues that were associated with cage formation between humans and rainbow trout, implying their similar manners in binding to m6A modification. Additionally, the results of qPCR experiment indicated that the expression patterns of a few YTH domain-containing genes, especially OmDF1b, OmDF3a and OmDF3b, were significantly different in liver tissue of rainbow trout under four different temperatures (7 °C, 11 °C, 15 °C, and 19 °C). The expression levels of OmDF1a, OmDF1b and OmDC1a were obviously repressed in spleen tissue of rainbow trout at 24 h after Yersinia ruckeri infection, while increased expression was detected in OmDF3b. This study provides a systemic overview of YTH domain-containing genes in rainbow trout and reveals their biological roles in responses to temperature stress and bacterial infection.

Neurobehavioral disorders induced by environmental zinc in female zebrafish (Danio rerio): Insights from brain and intestine transcriptional and metabolic signatures.

Human activities can cause zinc (Zn) contamination of aquatic environments. Zn is an essential trace metal, but effects of environmentally relevant Zn exposure on the brain-intestine axis in fish are poorly understood. Here, six-month-old female zebrafish (Danio rerio) were exposed to environmentally relevant Zn concentrations for six weeks. Zn significantly accumulated in the brain and intestine, causing anxiety-like behaviors and altered social behaviors. Zn accumulation altered levels of neurotransmitters, including serotonin, glutamate, and γ-aminobutyric acid, in the brain and intestine, and these changes were directly associated with changes in behavior. Zn caused oxidative damage and mitochondrial dysfunction, and impaired NADH dehydrogenase, thereby dysregulating the energy supply in brain. Zn exposure resulted in nucleotide imbalance and dysregulation of DNA replication and the cell cycle, potentially impairing the self-renewal of intestinal cells. Zn also disturbed carbohydrate and peptide metabolism in the intestine. These results indicate that chronic exposure to Zn at environmentally relevant concentrations dysregulates the bidirectional interaction of the brain-intestine axis with respect to neurotransmitters, nutrients, and nucleotide metabolites, thereby causing neurological disorder-like behaviors. Our study highlights the necessity to evaluate the negative impacts of chronic environmentally relevant Zn exposure on the health of humans and aquatic animals.

Nanoplastics promote arsenic-induced ROS accumulation, mitochondrial damage and disturbances in neurotransmitter metabolism of zebrafish (Danio rerio).

As a carrier, nanoplastics (NPs) can adsorb other toxic substances and thus modify their biological toxicity. Numerous studies have investigated the neurotoxic of high concentrations of arsenic (As, 2.83 mg/L-5 mg/L). However, it is still unknown whether the relatively low environmentally relevant concentrations of As (200 µg/L) can damage the structure and function of fish brains with the presence of NPs. In this study, zebrafish were exposed to polystyrene NPs, As and their mixture for 30 days respectively. Firstly, we found that the presence of NPs promoted the accumulation of As in zebrafish brains. Thereby the co-exposure of NPs and As further promoted the production of reactive oxygen species (ROS) in zebrafish brains compared with the single exposure of NPs or As, resulting in severe oxidative stress. Moreover, accumulated ROS directly damaged the mitochondrial membrane and mtDNA in zebrafish brains. Moreover, the mitochondrial damage was further aggravated due to inhibited mitochondrial fusion and activated mitochondrial division and mitophagy. Ultimately, the co-exposure led to mitochondrial damage in the zebrafish brain. Damaged mitochondria may not meet the high energy metabolic requirement for neuronal function. As a result, the normal function of nerve cells was adversely affected and eventually cell apoptosis may occur. Besides, the co-exposure caused more significant structural alterations in zebrafish brain tissue. Finally, the co-exposure of NPs and As caused abnormal biosynthesis and degradation of dopamine and acetylcholine. These resulted in decreased dopamine levels and increased acetylcholine levels in zebrafish brains. In conclusion, the presence of NPs promoted the accumulation of As, thereby inducing severe oxidative stress, which caused structural alterations and mitochondrial damage in the zebrafish brain, thus disordering neuromodulation, which may ultimately cause neurological dysfunction in zebrafish. This study will provide a risk assessment for evaluating the biotoxicity of NPs and As to fish and even other animals.

[Clinical application of anterolateral thigh perforator flap pedicled with oblique branch in intramuscular of lateral circumflex femoral artery].

Objective: To explore the characteristics and clinical application of the anterolateral thigh flap pedicled with the oblique branch in the intramuscular of lateral circumflex femoral artery. Methods: The clinical data of 25 patients with skin and soft tissue defects of extremities admitted between December 2020 and April 2021 were retrospectively analyzed, including 16 males and 9 females, aged 14-75 years, with the median age of 43 years. The defect site included 13 cases of hand, 2 cases of forearm, 2 cases of calf, and 8 cases of foot and ankle. The wound area ranged from 6 cm×4 cm to 35 cm×22 cm. Twenty-four patients with trauma were admitted to hospital immediately after injury, and 1 patient with diabetic foot infection was transferred to the hospital after ineffective treatment in other hospital. Flap surgery was performed from 0 to 56 days (median, 22 days) after admission. A total of 26 thigh flaps were harvested in 25 patients, with unilateral flaps in size of 7 cm×5 cm to 40 cm×10 cm. The type, caliber, and location of the perforating branch were recorded during the operation, and the anatomical characteristics of the oblique branch of the intramuscular trunk were mainly observed. The flap harvesting time was recorded; the flap survival and wound healing time were observed; at last follow-up, XIAO Feipeng et al. flap comprehensive efficacy evaluation table was used to evaluate the effectiveness of flap repair from three aspects of donor site, recipient site, and subjective satisfaction of doctors and patients. Results: After the oblique branch in intramuscular of lateral circumflex femoral artery was sent out, it ran 2-3 cm obliquely laterally and inferiorly in the intermuscular septum and then entered the vastus lateralis muscle, and sent out perforating branches to nourish the skin. A total of 61 perforating branches were marked in 26 thighs of 25 patients before operation, and 70 perforating branches were found during operation, including 9 transverse branches, 29 descending branches, and 32 oblique branches, all of the oblique branches were musculocutaneous perforators. All 25 patients were followed up 6-10 months, with an average of 8 months. The time of unilateral thigh flap harvesting ranged from 13 to 90 minutes, with an average of 48 minutes. One patient with diabetes developed disturbance of blood supply and complete necrosis of the flap at 1 month after operation, and then the flap was repaired with skin graft; 1 case developed arterial crisis after operation, which survived after timely exploration; and the rest of the flaps survived smoothly. The wound healing time of the recipient site ranged from 10 to 44 days, with an average of 19 days, and the donor site of the thigh healed by first intention. At last follow-up, the color and texture of the flap was good and the sensation recovered to S 1-S 2. Only linear scar was left in the donor site, no scar contracture, pain, and other discomfort occurred, and no other serious complications occurred. Evaluated by flap comprehensive efficacy evaluation table, the score was 74-93, with an average of 88, of which 10 cases were excellent, 13 cases were good, and 2 cases were fair, with an excellent and good rate of 92%. Conclusion: The intramuscular trunk oblique branch is not uncommon, and its trunk course and perforators distribution are regular. To improve the understanding of this type of oblique branch and adopt appropriate methods during operation can improve the success rate of skin flap extraction.

Selenium improved mitochondrial quality and energy supply in the liver of high-fat diet-fed grass carp (Ctenopharyngodon idella) after heat stress.

This study aims to explore the effects of dietary selenium on hepatic mitochondrial quality and energy supply of grass carp (Ctenopharyngodon idella) fed with high-fat diet (HFD) after heat stress (HS). Grass carp were fed with HFD, and HFD contained 0.3 mg/kg nano-selenium for 10 weeks, thereafter exposed to HS from 26 to 34 °C, and named the HFD + HS (control) group and the HFD + Se + HS group, respectively. The results show that selenium significantly prompted the growth, increased glutathione peroxidase (GPX) activity, but reduced malondialdehyde (MDA) content in the liver and the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the serum of grass carp fed with HFD after HS. Further, selenium alleviated mitochondrial damage and increased the number of mitochondrial DNA copies in the liver of the grass carp fed with HFD after HS. And selenium also maintained mitochondrial homeostasis by upregulating the expression of mitochondrial quality control-related genes (pgc-1α, nrf1/2, tfam, opa1, mfn1/2, and drp1), mitophagy-related genes (beclin1, atg5, atg12, pink1, and parkin), and the protein expression of parkin and LC3-II/I in the liver of grass carp. Finally, selenium reduced the triglyceride (TG) level and increased the free fatty acid (FFA) level and adenosine triphosphate (ATP) production in the liver of grass carp fed with HFD after HS. In conclusion, dietary selenium alleviated liver damage and improved liver mitochondrial quality and ATP production by increasing liver antioxidant capacity and promoting liver mitochondrial quality in grass carp fed with HFD after HS, which help grass carp to resist these two stressors.

Deep-sea cage culture altered microbial community composition in the sediments of the Yellow Sea Cold Water Mass.

Environmental impacts of the first submersible salmonid culture cage, which was launched in the deep-sea of the Yellow Sea Cold Water Mass, were investigated. The temporal and spatial variations of several physicochemical parameters were observed in both the bottom and sediment pore water. Aquaculture activities decreased bacterial richness in the sediment. The dominant phyla Proteobacteria, Desulfobacterota and Acidobacteriota, accounted for 30.42 % of the total bacteria community. Principal component analysis indicated that the bacterial composition in December was different from that in the other three months, and the aquaculture activity affected the distribution of the sediment microbial community in June, August and April. Planctomycetes was selected as biomarkers in the aquaculture area by linear discriminant analysis effect size. Redundancy analysis showed that the biomarkers were positively correlated with temperature and the concentration of nitrite in June, and negatively correlated with the dissolved oxygen in August and April.

Dynamic transcriptome and LC-MS/MS analysis revealed the important roles of taurine and glutamine metabolism in response to environmental salinity changes in gills of rainbow trout (Oncorhynchus mykiss).

Recently, the frequent salinity fluctuation has become a growing threat to fishes. However, the dynamic patterns of gene expression in response to salinity changes remain largely unexplored. In the present study, 18 RNA-Seq datasets were generated from gills of rainbow trout at different salinities, including 0 ‰, 6 ‰, 12 ‰, 18 ‰, 24 ‰ and 30 ‰. Based on the strict thresholds, we have identified 63, 1411, 2096, 1031 and 1041 differentially expressed genes in gills of rainbow trout through pairwise comparisons. Additionally, weighted gene co-expression network analysis was performed to construct 18 independent modules with distinct expression patterns. Of them, green and tan modules were found to be tightly related to salinity changes, several hub genes of which are known as the important regulators in taurine and glutamine metabolism. To further investigate their potential roles in response to salinity changes, taurine, glutamine, and their metabolism-related glutamic acid and α-ketoglutaric acid were accurately quantitated using liquid chromatography-tandem mass spectrometry analysis. Results clearly showed that their concentrations were closely associated with salinity changes. These findings suggested that taurine and glutamine play important roles in response to salinity changes in gills of rainbow trout, providing new insights into the molecular mechanism of fishes in salinity adaptation.

A hydroponic plants and biofilm combined treatment system efficiently purified wastewater from cold flowing water aquaculture.

Recently, more and more cold flowing water aquaculture has been adopted, but its wastewater treatment is always ignored, which causes great pressure on the environment. In this study, a compound in-situ treatment system that applied hydroponic plants and biofilm was constructed to treat the wastewater produced by cold flowing water culture of sturgeon. The removal efficiency of the nutrients from culture and the microbial composition in water and biofilm were tested, the correlation between the water quality indexes and bacterium was analyzed, and the abundance of nitrogen and phosphorus cycling genes was quantified. The results show that the system respectively achieved 90%, 100%, 100%, 100% and 48% removal efficiency of NH4+-N, NO3--N, TN, TP and COD which were produced by experimental sturgeon culture. Chinese cabbage (Brassica rapa var. chinensis) and water dropwort (Oenanthe javanica) showed obvious growth in the four plants, which contributed to the removal of nutrients from wastewater. Besides, in the biofilm, Proteobacteria, Bacteroidetes and Verrucomicrobia became the top three dominant flora at the phylum level, and Flavobacterium, Rhodoferax, Sphaerotilus and Chitinimonas became the top four dominant flora at the genus level, which promoted the removal of nitrogen in the wastewater. The FAPROTAX analysis result shows that the highest functions within the carbon and nitrogen metabolisms were significantly identified in the biofilm, such as chemoheterotrophy, aerobic chemoheterotrophy and nitrate reduction. Further, the abundance of denitrifying genes (narG and napA) was higher than the nitrifying related genes (nxrB and amoA), indicating the more active denitrifying process. In summary, the compound in-situ treatment system efficiently removed nutrients from cold flowing water aquaculture. And the combined purification of hydroponic plants and biofilm which is rich in denitrifying bacterium plays an essential role in this process.

Genome-Wide Analysis of Alternative Splicing (AS) Mechanism Provides Insights into Salinity Adaptation in the Livers of Three Euryhaline Teleosts, including Scophthalmus maximus, Cynoglossus semilaevis and Oncorhynchus mykiss.

Salinity is an important environmental factor that directly affects the survival of aquatic organisms, including fish. However, the underlying molecular mechanism of salinity adaptation at post-transcriptional regulation levels is still poorly understood in fish. In the present study, 18 RNA-Seq datasets were utilized to investigate the potential roles of alternative splicing (AS) in response to different salinity environments in the livers of three euryhaline teleosts, including turbot (Scophthalmus maximus), tongue sole (Cynoglossus semilaevis) and steelhead trout (Oncorhynchus mykiss). A total of 10,826, 10,741 and 10,112 AS events were identified in the livers of the three species. The characteristics of these AS events were systematically investigated. Furthermore, a total of 940, 590 and 553 differentially alternative splicing (DAS) events were determined and characterized in the livers of turbot, tongue sole and steelhead trout, respectively, between low- and high-salinity environments. Functional enrichment analysis indicated that these DAS genes in the livers of three species were commonly enriched in some GO terms and KEGG pathways associated with RNA processing. The most common DAS genes work as RNA-binding proteins and play crucial roles in the regulation of RNA splicing. The study provides new insights into uncovering the molecular mechanisms of salinity adaptation in teleosts.

Efficacy of using stable isotopes coupled with chemometrics to differentiate the production method and geographical origin of farmed salmonids.

The δ2H and δ18O of 105 salmonids cultured in freshwater and seawater and from different regions were combined with linear discriminant analysis (LDA), k-nearest neighbor (KNN), and random forest (RF) to create discrimination models. To assess the stability of the discrimination models, seasonal variation in δ2H and δ18O in salmonids cultured in different systems was studied. δ2H and δ18O were significantly different between salmonids cultured in freshwater and seawater and from different geographical origins. δ2H and δ18O of salmonids cultured in an open system were vulnerable to seasonal effects. The KNN model had 100% accuracy for identifying the production methods of salmonids and was less affected by seasonal variation. The RF model had the highest accuracy for identifying the geographical origins of salmonids with an accuracy of over 80%. Thus, δ2H and δ18O were more effective for identifying the production methods of salmonids than their geographical origins.