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Introduction: The aim of this research was to clarify the mechanism through which baicalin exerts its inhibitory effects on Aeromonas hydrophila infection. Methods: The antibacterial efficacy of baicalin was assessed by determining its minimum inhibitory concentration (MIC) against A. hydrophila. Various parameters, including the growth curve, cell wall integrity, biofilm formation, AKP content, and morphological alterations of A. hydrophila, were analyzed. In vivo experiments involved the administration of A. hydrophila 4 h postintraperitoneal injection of varying doses of baicalin to induce infection, with subsequent monitoring of mortality rates. After a 3 d period, liver, spleen, and intestinal tissues were harvested to evaluate organ indices, antioxidant and immune parameters, as well as intestinal microbial composition. Results: The findings indicated that baicalin treatment resulted in the disruption of the cell wall of A. hydrophila, leading to the loss of its normal structural integrity. Furthermore, baicalin significantly inhibited biofilm formation and facilitated the release of intracellular proteins (P < 0.05). In vivo, baicalin enhanced the survival rates of yellow catfish infected with A. hydrophila. Compared to the control group, the liver index of yellow catfish was elevated, while the spleen and intestinal indices were reduced in the baicalin-treated group (P < 0.05). Additionally, baicalin at an appropriate dosage was found to increase levels of SOD, GSH, CAT, ACP, and AKP in yellow catfish (P < 0.05), while simultaneously decreasing MDA accumulation and the mRNA expression of inflammatory markers such as Keap1, IL1, IFN-g, and TNF-a, (P < 0.05). Moreover, baicalin significantly enhanced the operational taxonomic unit (OTU) count in A. hydrophila-infected yellow catfish (P < 0.05), restoring the abundance of Barnesiellaceae, Enterobacteriaceae, Plesiomonas, and UBA1819 (P < 0.05). Discussion: In summary, baicalin demonstrates the potential to improve the survival rate of yellow catfish subjected to A. hydrophila infection, augment antioxidant and immune responses, mitigate inflammation, and enhance intestinal microbial diversity. [ABSTRACT FROM AUTHOR]

Nutritional programming has the potential to enhance digestible carbohydrate utilization in fish; however, the underlying mechanisms remain unclear. The present study compared the metabolome, glucose metabolism-related gene expressions, and global DNA methylation between yellow catfish larvae, which were parental programmed by a high carbohydrate diet (HC) or not (CON). In total, 1509 differentially altered metabolites (DAMs) were identified. Among them, the contents of key intermediates of TCA cycle and pentose phosphate pathway, citrate, and D-glycero-L-galacto-octulose were higher in HC than in CON. Meanwhile, the contents of two epigenetic modification-related metabolites, 2-hydroxyglutaric acid and N1-acetylspermidine, differed significantly between HC and CON. Thirteen KEGG pathways were significantly enriched and were mainly linked to amino acid and lipid metabolism. Additionally, the pentose phosphate pathway was enriched. The mRNA expressions of glycolytic genes gk, pk, and pfk, as well as the glucose transport gene sglt1, were significantly higher in HC than in CON. Global DNA methylation was significantly higher in HC than in CON. These results suggested that high carbohydrate programming could improve glucose utilization in yellow catfish larvae by modulating the TCA cycle and pentose phosphate pathway, and enhancing the conversion of glucose to amino acids. Epigenetic modifications might be the underlying mechanisms by which nutritional programming affects glucose metabolism in fish, while 2-hydroxyglutaric acid and N1-acetylspermidine are two critical metabolites that mediate epigenetic modifications. [ABSTRACT FROM AUTHOR]

Background: Mitochondria and endoplasmic reticulum (ER) contact sites (MERCS) constitute a functional communication platform for ER and mitochondria, and they play a crucial role in the lipid homeostasis of the liver. However, it remains unclear about the exact effects of MERCs on the neutral lipid synthesis of the liver. Methods: In this study, the role and mechanism of MERCS in palmitic acid (PA)-induced neutral lipid imbalance in the liver was explored by constructing a lipid metabolism animal model based on yellow catfish. Given that the structural integrity of MERCS cannot be disrupted by the si-mitochondrial calcium uniporter (si-mcu), the MERCS-mediated Ca2+ signaling in isolated hepatocytes was intercepted by transfecting them with si-mcu in some in vitro experiments. Results: The key findings were: (1) Hepatocellular MERCs sub-proteome analysis confirmed that, via activating Ip3r-Grp75-voltage-dependent anion channel (Vdac) complexes, excessive dietary PA intake enhanced hepatic MERCs. (2) Dietary PA intake caused hepatic neutral lipid deposition by MERCs recruiting Seipin, which promoted lipid droplet biogenesis. (3) Our findings provide the first proof that MERCs recruited Seipin and controlled hepatic lipid homeostasis, depending on Ip3r-Grp75-Vdac-controlled Ca2+ signaling, apart from MERCs's structural integrity. Noteworthy, our results also confirmed these mechanisms are conservative from fish to mammals. Conclusions: The findings of this study provide a new insight into the regulatory role of MERCS-recruited SEIPIN in hepatic lipid synthesis via Ip3r-Grp75-Vdac complex-mediated Ca2+ signaling, highlighting the critical contribution of MERCS in hepatic lipid homeostasis. [ABSTRACT FROM AUTHOR]

Simple Summary: Spermatozoa cryopreservation technology has been widely used to preserve high-quality male spermatozoa and has to some extent solved the problem of spermatozoa supply in yellow catfish (Pelteobagrus fulvidraco). However, cryopreservation can still cause cellular damage and affect spermatozoa viability and fertility. Therefore, it is necessary to study cryo-injury, which is beneficial for further optimizing the spermatozoa cryopreservation protocol. In this experiment, we investigated the effects of adding or not adding 10% DMSO on spermatozoa motility, ultrastructural damage, oxidative damage, and DNA damage of thawed yellow catfish. Using 10% DMSO as a cryoprotectant can improve spermatozoa motility (75.64 ± 1.12), significantly alleviate injuries to organelles and membrane structures, improve SOD (7.99 × 104 ± 5.24 nmol/mgprot) and T-AOC (3.7 × 105 ± 0.06 nmol/mgprot) enzyme activity, reduce MDA (1.09 ± 0.45 nmol/mgprot) enzyme activity, and mitigate the degree of oxidative damage. It also greatly reduces the DNA fragmentation rate (59 ± 1.56%). The research results provide data support for the optimization of the cryopreservation protocol for the spermatozoa of yellow catfish, which is beneficial for the preservation of the germplasm resources of yellow catfish and the effective utilization of resources during large-scale production. Spermatozoa cryopreservation protocols have been established for yellow catfish (Pelteobagrus fulvidraco), but cryopreservation can still cause cellular damage and affect spermatozoa viability and fertility. Therefore, the aim of this paper was to evaluate the effects of adding or not adding cryoprotectants during low-temperature storage on the ultrastructural damage, oxidative damage, and DNA damage of thawed yellow catfish spermatozoa. The mixed semen of three male yellow catfish was divided into a fresh spermatozoa group, a frozen spermatozoa group (DMSO+) with a cryoprotectant (10% DMSO), and a frozen spermatozoa group without a cryoprotectant (DMSO−). Ultrastructural of the spermatozoa after thawing were observed under an electron microscope and the spermatozoa were assayed for SOD, MDA, and T-AOC enzyme activities, as well as for DNA integrity. In terms of movement parameters, compared with DMSO−, the addition of DMSO has significantly improved sperm motility, curve line velocity (VCL), and straight line velocity (VSL). The ultrastructural results showed that although thawed spermatozoa exhibited increased damage than fresh spermatozoa, 10% DMSO effectively reduced the damage to the plasma membrane, mitochondria, and flagellum of spermatozoa by cryopreservation, and most of the spermatozoa were preserved with intact structure. The results of oxidative damage showed that compared with frozen spermatozoa, 10% DMSO significantly increased the activities of SOD and T-AOC enzymes and clearly reduced the activity of the MDA enzyme. The antioxidant capacity of spermatozoa was improved, lipid peroxidation was reduced, and the oxidative damage caused by cryopreservation was mitigated. The DNA integrity of spermatozoa showed that 10% DMSO clearly reduced the DNA fragmentation rate. In conclusion, 10% DMSO can effectively reduce the ultrastructural damage, oxidative damage, and DNA damage of yellow catfish spermatozoa during cryopreservation; it can also further optimize the cryopreservation protocol for yellow catfish spermatozoa. Meanwhile, it also provides a theoretical basis for the future optimization of the cryopreservation protocols. [ABSTRACT FROM AUTHOR]

Objective: Flathead Catfish Pylodictis olivaris are a widespread aquatic invasive species within the United States and a recent invader in the Susquehanna River basin, Pennsylvania. Flathead Catfish are piscivores known to consume native and recreationally important fish species. In the mid‐Atlantic United States, it is unknown how this invader is impacting food webs and which species may be at greatest predation risk. To address this knowledge gap, we DNA barcoded stomach contents collected from Flathead Catfish to identify prey species and elucidate potential predatory impacts of Flathead Catfish in the Susquehanna River. Methods: We used a Bayesian hierarchical multivariate probit model to investigate if the probability of prey species occurrence in the diets of Flathead Catfish varied seasonally or was a function of Flathead Catfish length. Result: A total of 576 Flathead Catfish were collected during 2020–2021, with 241 individuals having recoverable stomach contents. In all, we identified 47 different prey species. The most common prey species were rusty crayfish Faxonius rusticus, Margined Madtom Noturus insignis, and shiners Notropis spp. While frequency of occurrence of prey species differed across Flathead Catfish length classes (<300 mm, 301–600 mm, 601–900 mm TL), rusty crayfish were commonly found (33.7–44.0% of diets) in stomachs of all size‐classes. Conclusion: We found that Flathead Catfish length and seasonality did influence occurrence probability differentially for several prey species. For example, Channel Catfish Ictalurus punctatus were more likely to appear in shorter Flathead Catfish while Smallmouth Bass Micropterus dolomieu appeared in larger Flathead Catfish. We demonstrate significant variation in Flathead Catfish predation, increasing our understanding of predator–prey dynamics, which is necessary to better manage and identify future impacts to aquatic communities in the Susquehanna River basin. Impact statementInvasive Flathead Catfish are consuming a diverse set of prey in the Susquehanna River basin, Pennsylvania. Identifying species at risk of predation is useful for considering future ecological impacts. [ABSTRACT FROM AUTHOR]

Controlled release of curcumin by a pH-sensitive carrier provides long-term preservation, which extends the shelf lives of fish. FTIR, XRD, 1H NMR, zeta potential, swelling ratio, and TG analyses indicated that a pH-sensitive starch-based carrier with a narrow pH-sensitivity range (pH 6–7) was fabricated from the carboxymethyl starch grafted with methacrylic acid and then cross-linked with β-cyclodextrin to achieve dual functionality. FTIR, XRD, and fluorescence spectroscopy revealed that the mechanism by which curcumin was encapsulated in the starch-based carriers involved hydrophobic interactions and intermolecular hydrogen bonding. The encapsulated curcumin showed improved stability, higher antioxidant activity, antibacterial activity, and biocompatibility. The pH, TVB-N, TVC, and drip loss tests confirmed that the use of the carrier-curcumin complex at a concentration of 10 mg/mL for the preservation of yellow catfish extended the shelf life for 2–4 days during cold storage and improved the storage quality of the resulting fillets. This work provides a dual functionality strategy for constructing a pH-sensitive starch-based carrier to deliver curcumin and offers a promising choice for fish preservation. [ABSTRACT FROM AUTHOR]

Continuously feed-based aquaculture leads to excessive nitrogen and phosphate loads, degrading the culture environment. In this study, lotus (Nelumbo nucifera Gaertn) was planted in yellow catfish (Pelteobagrus fulvidraco Richardson) culture ponds to construct an integrated agriculture–aquaculture system to reduce nutrient accumulation and remediate the aquacultural environment. Results showed that additional lotus cultivation significantly reduced TN and TP concentrations in the pond water by 51.81% and 34.68%, respectively. Meanwhile, the concentrations of NH4+-N, TN, and TP in the sediment of co-culture ponds significantly decreased by 54.12%, 8.55%, and 10.85%, respectively, at the conclusion of the experiment period. Additionally, with the growth of lotus, the co-culture ponds exhibited significantly lower nitrogen and phosphorus fluxes across the sediment–water interface. Spearman correlation analysis revealed a significant positive correlation between the NH4+-N flux and TN concentration in the water and between TN flux and NO3−-N concentration in the water, respectively. This study suggests that the lotus-fish co-culture offers an optimal integrated agriculture–aquaculture system capable of mitigating excessive nutrient loads and improving the aquacultural environment. [ABSTRACT FROM AUTHOR]

Fatty acid desaturases (FADs) are rate-limiting enzymes for the biosynthesis of highly unsaturated fatty acids (HUFAs). As a new member of the FAD family, Fad6 and its roles remain unclear in various teleost fishes. In this study, we identified a fad6 gene from yellow catfish (ycfad6) and determined its spatiotemporal expression patterns and responses to different initial diets and nutritional status in yellow catfish. Our results showed that the open reading frame (ORF) of ycfad6 was 1,080 bp in length, encoding a protein of 359 amino acids. Multiple protein sequences alignment proved that fad6 is highly conserved among diverse vertebrates. Meanwhile, phylogenetic analysis revealed that Southern catfish and yellow catfish were clustered into one branch, supporting evolutionary consistence between the fad6 gene and fish morphology. Moreover, comparisons of genomic synteny and gene structure revealed functional and evolutionary conservation of the fad6 gene in various teleost fishes. Tissue distribution analysis by quantitative RT-PCR demonstrated that the ycfad6 gene was extensively expressed in examined tissues, with higher transcription levels in the heart and liver. Meanwhile, ycfad6 gene was widely expressed in various developmental stages, indicating Fad6 may play important roles in HUFA biosynthesis at early developmental stages in yellow catfish. Functional experiments verified that the transcription of ycfad6 decreased significantly with the extension of feeding time (with egg yolk or Artemia nauplii) at the early developmental stages, indicating that a diet rich in HUFA can remarkably inhibit the transcription of ycfad6 in yellow catfish. In addition, ycfad6 transcription was significantly reduced after a short-term (24-h) or long-term food deprivation (1-week) and then continued to decrease during refeeding, suggesting that nutritional states can affect the transcription of ycfad6, which further regulates the metabolism of HUFAs. Anyway, these fundamental findings provide basic references for further investigating evolutionary and physiological functions of the fad6 gene in yellow catfish as well as in other teleost fishes. [ABSTRACT FROM AUTHOR]

Population genetic analysis of invasive populations can provide valuable insights into the source of introductions, pathways for expansion, and their demographic histories. Flathead catfish (Pylodictis olivaris) are a prolific invasive species with high fecundity, long‐distance dispersal, and piscivorous feeding habits that can lead to declines in native fish populations. In this study, we analyse the genetics of invasive P. olivaris in the Mid‐Atlantic region to assess their connectivity and attempt to reconstruct the history of introduced populations. Based on an assessment across 13 microsatellite loci, P. olivaris from the Susquehanna River system (N = 537), Schuylkill River (N = 33), and Delaware River (N = 1) have low genetic diversity (global Hobs = 0.504), although we detected no evidence of substantial inbreeding (FIS = −0.083 to 0.022). P. olivaris from these different river systems were genetically distinct, suggesting separate introductions. However, population structure was much weaker within each river system and exhibited a pattern of high connectivity, with some evidence of isolation by distance. P. olivaris from the Susquehanna and Schuylkill rivers showed evidence for recent genetic bottlenecks, and demographic models were consistent with historical records, which suggest that populations were established by recent founder events consisting of a small number of individuals. Our results show the risk posed by small introductions of P. olivaris, which can spread widely once a population is established, and highlight the importance of prevention and sensitive early detection methods to prevent the spread of P. olivaris in the future. [ABSTRACT FROM AUTHOR]

The purpose of this study was to measure organ blood flow (OBF) in yellow catfish (YC, Pelteobagrus fulvidraco), largemouth bass (LB, Micropterus salmoides), and grass carp (GC, Ctenopharyngodon idella) using the method of fluorescent microspheres. Yellow–green microspheres were injected into the fish via cardiac catheterization using a syringe pump at a rate of 0.8 mL/min. Reference blood samples were collected from the dorsal aorta, and fish tissues were harvested after 5 min and processed for fluorescence spectrophotometric analysis. The results showed that the OBF of the heart increased significantly with the increase in temperature from 20 to 30 °C, while there was no significant difference in the OBF of other organs/tissues in YC. The OBFs of different species of LB and GC were also determined at 25 °C. In GC, the blood flow rates of the heart, spleen, kidney, liver, others, gills, swim bladder, intestines, muscles, and skin were 9.55, 1.00, 10.3, 6.92, 6.70, 6.04, 2.06, 2.81, 1.78, and 3.72 (mL/min/g), respectively. In LB, the blood flow rates of the same organs were 8.80, 2.33, 1.01, 0.71, 4.11, 2.72, 1.22, 0.54, 9.47, and 0.40 (mL/min/g), respectively. Compared to the OBFs of YC at 25 °C, the OBFs in GC were the highest, followed by LB. These results reflect that OBF in fish has significant species differences. These studies provide fundamental physiological data on OBFs in YC, GC, and LB, which has practical implications for improving the development of disciplines associated with fish physiology. [ABSTRACT FROM AUTHOR]

Simple Summary: Although the prevalence of hybrid sterility in fish is a serious limitation to the quality development of the hybrid fish farming industry, it could be useful for the conservation of the genetic stock of endangered and valuable species. In this study, a total of 1709 DEGs were identified by performing RNA sequencing between hybrid and two pure yellow catfishes. A KEGG pathway analysis indicated that some genes related to reproductive functions were upregulated, including genes involved in the cell cycle and oocyte meiosis, whereas genes related to ECM–receptor interactions were downregulated. In total, 63 DEmiRNAs were obtained between the three species of yellow catfishes. The upregulated DEmiRNAs ipu-miR-194a and ipu-miR-499 were found to target the spermatogenesis-related genes CFAP70 and RSPH6A, respectively. Both acted as negative regulators, and this may underscore the miRNA–mRNA regulatory mechanism of sterility in hybrid yellow catfish (P. fulvidraco ♀ × P. vachelli ♂). The hybrid yellow catfish exhibits advantages over pure yellow catfish in terms of fast growth, fast development, a high feeding rate, and strong immunity; additionally, it is almost sterile, thus ensuring the conservation of the genetic stock of fish populations. To investigate the sterility mechanism in hybrid yellow catfish (P. fulvidraco (♀) × P. vachelli (♂)), the mRNA and miRNA of the gonads of P. fulvidraco, P. vachelli, and a hybrid yellow catfish were analyzed to characterize the differentially expressed genes; this was carried out to help establish gene expression datasets to assist in the further determination of the mechanisms of genetic sterility in hybrid yellow catfish. In total, 1709 DEGs were identified between the hybrid and two pure yellow catfishes. A KEGG pathway analysis indicated that several genes related to reproductive functions were upregulated, including those involved in the cell cycle, progesterone-mediated oocyte maturation, and oocyte meiosis, and genes associated with ECM–receptor interaction were downregulated. The spermatogenesis-related GO genes CFAP70, RSPH6A, and TSGA10 were identified as being downregulated DEGs in the hybrid yellow catfish. Sixty-three DEmiRNAs were identified between the hybrid and the two pure yellow catfish species. The upregulated DEmiRNAs ipu-miR-194a and ipu-miR-499 were found to target the spermatogenesis-related genes CFAP70 and RSPH6A, respectively, playing a negative regulatory role, which may underscore the miRNA–mRNA regulatory mechanism of sterility in hybrid yellow catfish. The differential expression of ipu-miR-196d, ipu-miR-125b, and ipu-miR-150 and their target genes spidr, cep85, and kcnn4, implicated in reproductive processes, was verified via qRT-PCR, consistent with the transcriptome sequencing expression trends. This study provides deep insights into the mechanism of hybrid sterility in vertebrate groups, thereby contributing to achieving a better understanding and management of fish conservation related to hybrid sterility. [ABSTRACT FROM AUTHOR]

Simple Summary: Personality and light are crucial to ensure the welfare of aquatic animals. To understand how personality affects the light color selection of fish, we tested the behaviors with different personalities under six colors of light: violet (410–420 nm), yellow (580–590 nm), green (550–560 nm), red (620–630 nm), blue (470–480 nm), and white. In this study, the yellow catfish Pelteobagrus fulvidraco preferred the yellow and green light over the other light colors. After identifying their preferred light colors, bold individuals reduced their frequency of exploration. The results showed that bold individuals could make a quick decision for light color selection. This study provides a reference for the welfare of juvenile yellow catfish in aquaculture. Personality, which matters for animal welfare, demonstrates behavioral differences. Light is one of the most important factors in aquaculture. However, how fish personality affects light color selection is unclear. In this study, we tested the personality of yellow catfish Pelteobagrus fulvidraco juveniles and then quantified the selective behaviors of different personalities under six light colors: violet (410–420 nm), yellow (580–590 nm), green (550–560 nm), red (620–630 nm), blue (470–480 nm), and white. The results showed that juveniles preferred the yellow and green light over the other colors of light, probably due to different reasons. The average cumulative dwell time in yellow (32.81 ± 5.22%), green (21.81 ± 3.58%), and red (26.36 ± 4.89%) lights was significantly longer than the other light colors, and the average visit frequency in green light (32.00 ± 4.93%) was the most. Juveniles had the longest total moved distance in green light. Moreover, the results demonstrated that shy and bold individuals had the same preference for the green light. Bold individuals could find the preferred light colors rapidly and make quick decisions for light color selection. After identifying the preferred light colors, bold individuals reduced the frequency of exploration. This study provides a theoretical basis for the welfare of juvenile yellow catfish in aquaculture. [ABSTRACT FROM AUTHOR]

Enrofloxacin (ENR) residues in yellow catfish (Pelteobagrus fulvidraco) often exceed the standard due to excessive use. This study explored the pharmacokinetics of ENR and its metabolite ciprofloxacin (CIP) in yellow catfish following a single dose of 10 mg/kg body weight via intramuscular injection (IM), oral gavage (PO), or a 5‐h drug bath at 10 mg/L and 25°C. High‐performance liquid chromatography‐mass spectrometry was used to determine the ENR and CIP concentrations in various tissues. The highest ENR concentration occurred with IM administration, peaking at 4.124 mg/L in the plasma, 8.359 mg/kg in the kidney, 6.272 mg/kg in the liver, and 5.192 mg/kg in the muscle. However, PO administration resulted in the longest metabolic time, with elimination half‐lives of 56.47 h in plasma, 86.43 h in the kidney, 76.25 h in the liver, and 64.75 h in muscle. Additionally, the area under the concentration–time curve values for IM, PO, and bath administration in yellow catfish plasma were 108.36, 88.96, and 22.08 mg·h/L, respectively. These results indicate the effectiveness of all three administration methods in treating bacterial diseases in yellow catfish. The selection of an appropriate administration method depends on the minimal inhibitory concentration of ENR against pathogenic bacteria. Yellow catfish subjected to PO and IM administration require longer resting periods before they can be marketed than those receiving drug bath administration. [ABSTRACT FROM AUTHOR]

This experiment investigated the influences of different dietary fat levels on histology, oxidative status, and immune response in gill and kidney of yellow catfish (Pelteobagrus fulvidraco). Three diets with different fat levels of 63.1 g/kg (low-fat, LF), 93.3 g/kg (medium-fat, MF), and 153.2 g/kg (high-fat, HF) were prepared to feed yellow catfish. The experiment continued for 56 days, and at the end of the experiment, gill and kidney tissues were sampled. As a result, both gill and kidney showed different degrees of tissue damage in HF group in terms of histology observation. HF increased the malondialdehyde content in gill but showed no effect on kidney, indicating that gill is more susceptible to injury than kidney under high-energy intake conditions. Additionally, HF diet significantly increased the activities of total-superoxide dismutase and catalase to eliminate excess peroxides both in gill and kidney. Moreover, HF diet significantly upregulated the expressions of pro-inflammatory cytokines (il6 and tnfα) and downregulated the expression of anti-inflammatory cytokines (il10), indicating that HF-diet-induced inflammatory response both in gill and kidney. These findings reveal the potential regulatory approach for fish gill and kidney health by dietary fat level, which will help to understand the adverse impacts of dietary lipid imbalance on the health of fish. [ABSTRACT FROM AUTHOR]

Yellow catfish Tachysurus fulvidraco is an important commercial fish species in South Korea. However, due to their current declines in its distribution area and population size, it is being released from hatchery populations into wild populations. Hatchery populations also produced from wild broodstocks are used for its captive breeding. We reported 15 new microsatellite DNA markers of T. fulvidraco to identify the genetic diversity and structure of its hatchery and wild populations, providing baseline data for useful resource development strategies. The observed heterozygosity of the hatchery populations ranged from 0.816 to 0.873, and that of the wild populations ranged from 0.771 to 0.840. Their inbreeding coefficient ranged from −0.078 to 0.024. All populations experienced a bottleneck (p < 0.05), with effective population sizes ranging from 21 to infinity. Their gene structure was divided into two groups with STRUCTURE results of K = 2. It was confirmed that each hatchery population originated from a different wild population. This study provides genetic information necessary for the future development and conservation of fishery resources for T. fulvidraco. [ABSTRACT FROM AUTHOR]

The outbreak of mass mortality occurred in Tachysurus fulvidraco farm in Hubei province of China. The pathogenic strain of Streptococcus iniae (termed 2022SI08) was isolated and identified from diseased T. fulvidraco, based on morphological, physiological, and biochemical characteristics, as well as 16S rRNA gene sequence and phylogenetic analysis. Further, the whole genome of isolate S. iniae was sequenced and predicted to contain one single circular chromosome of 1,776,777 bp with a GC content of 37.14%. The genomic sequence analysis showed that 2022SI08 was positive for 204 virulent and 127 antibiotic resistant genes. The experimental challenge demonstrated the high pathogenicity of the retrieved isolate of S. iniae, with a median lethal dosage (LD50) 9.53 × 105 CFU/g. Histopathological examination indicated that the 2022SI08 strain could induce extensive tissue cell degeneration, necrosis, hemorrhage, and inflammation in the skin, gill, fin, spleen, liver, kidney, intestine, eye, and brain. Moreover, the innate immune enzyme activities in serum such as acid phosphatase and alkaline phosphatase were increased significantly at 24 and 48 h post infection (hpi) and then decreased at 168 hpi. The transcriptional profile of immune associated gene in T. fulvidraco following bacterial infection was detected at each point of time, and the results revealed clear transcriptional activation of those genes, which proving their reacting and regulatory role during the response of the host against S. iniae infection. The results revealed that S. iniae was an etiological agent in the mass mortalities of T. fulvidraco and this research will be conducive for increasing our understanding on pathogenesis and host defensive system in S. iniae invasion. [ABSTRACT FROM AUTHOR]

Simple Summary: Soybean meal is the most widely used plant protein source, but its application in aquaculture is limited by the existence of anti-nutrient factors. Fermentation can degrade the anti-nutrient factors in soybean meal. Yeast culture is a complex fermentation product, which is composed of yeast cells, metabolites and fermentation medium formed by multi-stage fermentation. Yeast culture contains plenty of β-glucan and mannan oligosaccharides, which can promote the growth, intestinal health and immunity of aquatic animals. This study investigated the potential of yeast culture substituting for fishmeal in the diet of yellow catfish (Pelteobagrus fulvidraco). The results showed that in the practical diet containing 160 g/kg fishmeal, yeast culture could effectively replace 40 g/kg fishmeal without adverse effects on the growth performance, nutrient utilization, serum biochemical indices, and intestinal and hepatopancreas histology of yellow catfish. Yeast culture is a complex fermentation product consisting of fermentation substrate, yeast cells and their metabolites. This study investigated the potential of yeast culture in replacing fishmeal in the diet of yellow catfish (Pelteobagrus fulvidraco). First, a basal diet was formulated to contain 160 g/kg fishmeal (CON), and then the dietary fishmeal was decreased to 120, 80, 40 and 0 g/kg via yeast culture inclusion, respectively, to form another four isonitrogenous and isolipidic diets (YC-12, YC-8, YC-4 and YC-0). Yellow catfish (3.00 ± 0.10 g) were fed with the above five diets with triplicates per treatment and 40 fish per replicate. After 8 weeks of feeding, the weight gain (WG), protein efficiency rate and protein retention in the YC-12 group and the feed conversion ratio (FCR) in the YC-12 and YC-8 groups showed no significant differences to the CON group (p > 0.05), but the WG in the YC-8, YC-4 and YC-0 groups was significantly lower, and the FCR in the YC-4 and YC-0 groups was significantly higher than in the CON group (p < 0.05). In terms of the whole-body composition, only the crude lipid content in the YC-0 group decreased significantly (p < 0.05). Compared with the CON group, the aspartate aminotransferase and alanine aminotransferase activities and D-lactic acid content in the YC-0 group were significantly increased, and the total cholesterol content was significantly reduced (p < 0.05). The activities of catalase, superoxide dismutase, and alkaline phosphatase, as well as the content of complement C3 and immunoglobulin M, were significantly increased, while the MDA content was significantly reduced in the YC-12 and YC-8 groups (p < 0.05). There were no significant differences in the intestinal amylase and lipase activity among all the groups (p > 0.05), while the trypsin activity in the YC-12 and YC-8 groups, as well as the diamine oxidase in the YC-4 and YC-0 groups, were significantly higher than those in the CON group (p < 0.05). In the intestine histology, there was a significant decrease in the intestinal villus height in the YC-4 and YC-0 groups as well as in the villus width in the YC-0 group (p < 0.05). In the hepatopancreas histology, lipid droplets appeared in the YC-4 and YC-0 groups, and severe cell vacuolation was observed in the YC-0 group. As a summary, in a practical diet containing 160 g/kg fishmeal, yeast culture can effectively replace 40 g/kg fishmeal without negatively affecting the growth performance, nutrient utilization, serum immune and antioxidant, intestinal and hepatopancreas histology of yellow catfish. [ABSTRACT FROM AUTHOR]

Due to the non-degradable and persistent nature of metal ions in the environment, they are released into water bodies, where they accumulate in fish. In order to assess pollution in fish, the enzyme, glucose 6-phosphate dehydrogenase (G6PD), has been employed as a biomarker due to sensitivity to various ions. This study investigates the kinetic properties of the G6PD enzyme in yellow catfish (Pelteobagrus fulvidraco), and analyzes the effects of these metal ions on the G6PD enzyme activity in the ovarian cell line (CCO) of channel catfish (Ictalurus punctatus). IC50 values and inhibition types of G6PD were determined in the metal ions Cu2+, Al3+, Zn2+, and Cd2+. While, the inhibition types of Cu2+ and Al3+ were the competitive inhibition, Zn2+ and Cd2+ were the linear mixed noncompetitive and linear mixed competitive, respectively. In vitro experiments revealed an inverse correlation between G6PD activity and metal ion concentration, mRNA levels and enzyme activity of G6PD increased at the lower metal ion concentration and decreased at the higher concentration. Our findings suggest that metal ions pose a significant threat to G6PD activity even at low concentrations, potentially playing a crucial role in the toxicity mechanism of metal ion pollution. This information contributes to the development of a biomonitoring tool for assessing metal ion contamination in aquatic species. [ABSTRACT FROM AUTHOR]

Yellow catfish (Pelteobagrus fulvidraco) is an important freshwater fish species in aquaculture. However, as intensive farming has rapidly expanded, infectious diseases caused by various bacteria, such as Aeromonas hydrophila, have also increased. We conducted a transcriptomic analysis of head kidney from P. fulvidraco stimulated by A. hydrophila strain SHOU. A total of 43,249 unigenes with an average length of 1342 bp were obtained following assembly and annotation. By analyzing GO and KEGG enrichment, many differentially expressed genes (DEGs) and pathways related to immunity were identified. Out of the 973 DEGs that were identified, 553 were upregulated and 420 were downregulated. Moreover, KEGG enrichment analysis revealed that the innate immune system, including the TNF signaling pathway, NF-kappa B signaling pathway, and the Toll-like receptor signaling pathway involved in the defense, is activated against infectious response. Real-time quantitative reverse transcription-PCR (qRT-PCR) analysis demonstrated that immune response genes were upregulated in response to A. hydrophila stimulation compared to the control. In conclusion, this study provides valuable insights into the immune defense mechanism of P. fulvidraco and sheds light on the host immune genes involved in the response to bacterial infection. [ABSTRACT FROM AUTHOR]

Lipophagy is a selective autophagy that regulates lipid metabolism and reduces hepatic lipid deposition. However, the underlying mechanism has not been understood in fish. In this study, we used micronutrient zinc (Zn) as a regulator of autophagy and lipid metabolism and found that Ras-related protein 7 (rab7) was involved in Zn-induced lipophagy in hepatocytes of yellow catfish Pelteobagrus pelteobagrus. We then characterized the rab7 promoter and identified binding sites for a series of transcription factors, including Forkhead box O3 (FOXO3). Site mutation experiments showed that the −1358/−1369 bp FOXO3 binding site was responsible for Zn-induced transcriptional activation of rab7. Further studies showed that inhibition of rab7 significantly inhibited Zn-induced lipid degradation by lipophagy. Moreover, rab7 inhibitor also mitigated the Zn-induced increase of cpt1α and acadm expression. Our results suggested that Zn exerts its lipid-lowering effect partly through rab7-mediated lipophagy and FA β-oxidation in hepatocytes. Overall, our findings provide novel insights into the FOXO3/rab7 axis in lipophagy regulation and enhance the understanding of lipid metabolism by micronutrient Zn, which may help to reduce excessive lipid accumulation in fish. [ABSTRACT FROM AUTHOR]

Sex control techniques are in great demand for aquaculture because of the huge benefits of mono-sex production. In a previous study on yellow catfish (Tachysurus fulvidraco), intersex individuals were produced by administrating 17a-methyltestosterone (MT) or aromatase inhibitor letrozole (LZ). The ovarian and testicular portions of intersexual gonads developed well and were completely separated, arousing our interest in producing selffertilizable fish and clone-like fish populations. In this study, yellow catfish fry were treated with a combination of MT and LZ at a low dose (5 mg kg-1 MT, 300 mg kg-1 LZ) at a low water temperature (27.0 °C, mixed sexproducing temperature, LL group) and a high temperature (33.5 °C, male-producing temperature, HL group), and with a high dose (10 mg kg-1 MT, 600 mg kg-1 LZ) at a low water temperature (LH group), during 12-65 days post-hatching, the critical period of sex differentiation. Both XX and XY intersex were produced with different percentages at the same time through co-treatment with MT and LZ, with or without the help of male-producing temperature. The highest percentage of XY intersex (53% in XY, 36% in XX and XY) and XX intersex (47% in XX, 25% in XX and XY) was produced in LH and HL groups, respectively. Results of gonadal morphology, histology, and sperm dynamic analysis indicate that some XX and XY intersex individuals were capable of self-fertilization through artificial insemination. The reproductive performance of these intersex individuals was then investigated by injecting spawning agents, dissecting gonads, and artificially fertilizing eggs with their own sperm. The XX, XY, and YY genotypic individuals were produced by the self-fertilization of XY intersex individuals. The present study successfully produced high percentages of XX and XY intersex and conducted self-fertilization by mating the eggs and sperm of a single intersex individual. Self-fertilization in fish will show great potential in aquaculture genetics and breeding, for example, generating highly homozygous (or "clonal") genetic material, producing mono-sex populations, and identifying unknown sex determination modes. In particular, the cloning method of producing genetic materials will be greatly beneficial for maintaining advantageous traits through self-fertilization generation after generation. [ABSTRACT FROM AUTHOR]

The effects of selenium supplementation in Tachysurus fulvidraco (T. fulvidraco) on low-temperature stress are not known. In this study, 280 healthy T. fulvidraco were divided into two groups, the G0 group (a control group) and the T0 group (a selenium treatment group on a 0.22 mg/kg diet), for a 6-week feeding time. Then, low-temperature stress (water temperature dropped from 26 to 13 °C, with a rate of 1 °C/h) was administered after that. The feeding results showed that selenium increased the percent weight gain (PWG), specific growth rate (SGR), and survival rate (SR) of T. fulvidraco and decreased the feed conversion rate (FCR), but these differences were not significant (p > 0.05). Under low temperatures, selenium still has no significant effects on antioxidant indexes such as glutathione peroxidase (GSH-Px) activity, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content in serum (p > 0.05). However, metabolomic analysis revealed that selenium caused changes in lipids and lipid-like molles, organic acids and their derivatives, and fatty acyls. Choline, linoleic acid, and glycerophospholipid metabolism pathways; d-arginine and d-ornithine metabolism; valine, leucine, and isoleucine degradation; and biosynthesis pathways, as well as pyrimidine metabolism pathways, were activated to produce these metabolites to combat against this stress. In addition, selenium increased the diversity of intestinal microbes in T. fulvidraco and decreased the relative abundance of Plesiomonas. However, the combined analysis showed the intestinal microbe changes did not affect metabolite production. In summary, selenium activated lipid, carbohydrate, and amino acid metabolism for energy substance provision, reduced the oxidation and production of other harmful substances, and increased the intestinal microbe diversity of T. fulvidraco to improve resistance to low-temperature stress. [ABSTRACT FROM AUTHOR]

Simple Summary: It is known that in highly pathogenic infections, the cAMP receptor protein (CRP) frequently plays an essential regulatory role. A highly pathogenic strain of Vibrio mimicus SCCF01 has been isolated from yellow catfish. To investigate the role of the cAMP receptor protein in regulating SCCF01, we created a strain with a deleted crp gene (Δcrp). The results demonstrated that the expression of genes related to the bacterial type II secretion system, flagellin, adhesion, and metalloproteinase was decreased by the deletion crp gene. The above resulted in modifications to the morphology of the bacteria and colonies, as well as a decrease in the motility, hemolytic activity, biofilm formation, bacterial growth, and enzyme activity. Animal experiments and cytotoxicity analyses verified that crp played a role in V. mimicus pathogenicity. In conclusion, these findings clarified the biological role of the crp gene in V. mimicus, revealed the pathogenic mechanism of the microorganism, and provided a basis for effective control and prevention of V. mimicus infection. Vibrio mimicus is a serious pathogen in aquatic animals, resulting in significant economic losses. The cAMP receptor protein (CRP) often acts as a central regulator in highly pathogenic pathogens. V. mimicus SCCF01 is a highly pathogenic strain isolated from yellow catfish; the crp gene deletion strain (Δcrp) was constructed by natural transformation to determine whether this deletion affects the virulence phenotypes. Their potential molecular connections were revealed by qRT-PCR analysis. Our results showed that the absence of the crp gene resulted in bacterial and colony morphological changes alongside decreases in bacterial growth, hemolytic activity, biofilm formation, enzymatic activity, motility, and cell adhesion. A cell cytotoxicity assay and animal experiments confirmed that crp contributes to V. mimicus pathogenicity, as the LD50 of the Δcrp strain was 73.1-fold lower compared to the WT strain. Moreover, qRT-PCR analysis revealed the inhibition of type II secretion system genes, flagellum genes, adhesion genes, and metalloproteinase genes in the deletion strain. This resulted in the virulence phenotype differences described above. Together, these data demonstrate that the crp gene plays a core regulatory role in V. mimicus virulence and pathogenicity. [ABSTRACT FROM AUTHOR]

An eight-week feeding experiment was conducted to evaluate the effects of replacing fish meal with stickwater hydrolysate (SWH) or stickwater hydrolysate meal (SWM) on the growth, serum biochemical parameters, intestinal digestive enzyme activity, and muscle quality of yellow catfish (Tachysurus fulvidraco). The control diet (CON) contained 30% fish meal and the remaining five diets were substituted for fish meal with 2.5% (SWM2.5), 5% (SWM5) SWM, and 5% (SWH5), 10% (SWH10), and 15% (SWH15) SWH, respectively. The results showed that there were no significant differences in weight gain rate, feed conversion rate, survival rate, hepatosomatic index, and viscerosomatic index among the groups. The substitution of fish meal with SWH significantly augmented the serum triglyceride and total cholesterol levels, whereas urea nitrogen content exhibited a reduction proportional to the replacement ratio. The incorporation of SWH led to a notable rise in glutamate-pyruvate transaminase activity, albeit with a gradual decline as the substitution ratio escalated. Relative to the CON group, the SWH5 group displayed a significant reduction in serum superoxide dismutase activity and a significant elevation in serum catalase activity. The substitution of fish meal with SWM yielded noticeable increments in the activities of complement 3, immunoglobulin M, and alkaline phosphatase. Neither SWH nor SWM exerted a substantial influence on intestinal amylase activity. Regarding muscle characteristics, neither SWH nor SWM showed a marked effect on hardness and springiness; however, adhesiveness, cohesiveness, gumminess, and chewiness properties exhibited enhancement as the proportion of fish meal replacement increased. In conclusion, within this experimental context, substituting fish meal with SWH and SWM did not adversely impact the growth and meat quality of yellow catfish. Specifically, replacing 15% fish meal with stickwater hydrolysate and 5% fish meal with stickwater hydrolysate meal contributed to an enhanced immune capacity in yellow catfish to a certain extent. [ABSTRACT FROM AUTHOR]

Objective: Proliferative gill disease (PGD) in Channel Catfish Ictalurus punctatus and hybrid catfish (Channel Catfish × Blue Catfish I. furcatus) is attributed to the myxozoan Henneguya ictaluri. Despite evidence of decreased H. ictaluri transmission and impaired parasite development in hybrid catfish, PGD still occurs in hybrid production systems. Previous metagenomic assessments of clinical PGD cases revealed numerous myxozoans within affected gill tissues in addition to H. ictaluri. The objective of this study was to investigate the development and pathologic contributions of H. ictaluri and other myxozoans in naturally and experimentally induced PGD. Methods: Henneguya species‐specific in situ hybridization (ISH) assays were developed using RNAscope technology. Natural infections were sourced from diagnostic case submissions in 2019. Experimental challenges involved Channel Catfish and hybrid catfish exposed to pond water from an active PGD outbreak, and the fish were sampled at 1, 7, 10, 12, 14, 16, 18, and 20 weeks postchallenge. Result: Nine unique ISH probes were designed, targeting a diagnostic variable region of the 18S ribosomal RNA gene of select myxozoan taxa identified in clinical PGD cases. Partial validation from pure H. ictaluri, H. adiposa, H. postexilis, and H. exilis infections illustrated species‐specific labeling and no cross‐reactivity between different myxozoan species or the catfish hosts. After experimental challenge, mature plasmodia of H. ictaluri and H. postexilis formed in Channel Catfish but were not observed in hybrids, suggesting impaired or delayed sporogenesis in the hybridized host. These investigations also confirmed the presence of mixed infections in clinical PGD cases. Conclusion: Although H. ictaluri appears to be the primary cause of PGD, presporogonic stages of other myxozoans were also present, which may contribute to disease pathology and exacerbate respiratory compromise by further altering normal gill morphology. This work provides molecular confirmation and more resolute developmental timelines of H. ictaluri and H. postexilis in Channel Catfish and supports previous research indicating impaired or precluded H. ictaluri sporogony in hybrid catfish. Impact statementThis work implicates Henneguya ictaluri as the primary cause of proliferative gill disease, a devastating parasitic disease of U.S. catfish aquaculture, but demonstrates other myxozoan parasites can contribute to disease severity. The study better defines the developmental timeline of H. ictaluri and H. postexilis in Channel Catfish and supports research indicating impaired maturation of H. ictaluri in hybrid catfish. [ABSTRACT FROM AUTHOR]

There is a pressing need for more‐holistic approaches to fisheries assessments along with growing demand to reduce the health impacts of sample collections. Metabolomic tools enable the use of sample matrices that can be collected with minimal impact on the organism (e.g., blood, urine, and mucus) and provide high‐throughput, untargeted biochemical information without the requirement of a sequenced genome. These qualities make metabolomics ideal for monitoring a wide range of fish species, particularly those under protected status. In the current study, we surveyed the relative abundances of 120 endogenous metabolites in epidermal mucus across eight freshwater fish species belonging to seven phylogenetic orders. Principal component analysis was used to provide an overview of the data set, revealing strong interspecies relationships in the epidermal mucous metabolome. Normalized relative abundances of individual endogenous metabolites were then used to identify commonalities across multiple species, as well as those metabolites that showed notable species specificity. For example, taurine was measured in high relative abundance in the epidermal mucus of common carp (Cyprinus carpio), northern pike (Esox lucius), golden shiner (Notemigonus crysoleucas), rainbow trout (Oncorhynchus mykiss), and rainbow smelt (Osmerus mordax), whereas γ‐amino butyric acid (GABA) exhibited a uniquely high relative abundance in flathead catfish (Pylodictis olivaris). Finally, hierarchical cluster analysis was used to evaluate species relatedness as characterized by both the epidermal mucous metabolome (phenotype) and genetic phylogeny (genotype). This comparison revealed species for which relatedness in the epidermal mucous metabolome composition closely aligns with phylogenetic relatedness (e.g., N. crysoleucas and C. carpio), as well as species for which these two measures are not well aligned (e.g., P. olivaris and Polyodon spathula). These, and other findings reported here, highlight novel areas for future research with fish, including development of epidermal mucous‐based markers for non‐invasive health monitoring, sex determination, and hypoxia tolerance. [ABSTRACT FROM AUTHOR]

Simple Summary: Rutin is a collection of natural compounds that possess a distinctive polyphenolic structure of flavonoids. The present preliminary study aimed to investigate the impact of dietary rutin supplementation on the growth performance, antioxidant capacity, and intestinal health of yellow catfish. Three diets supplemented with different levels of rutin (0, 100 mg/kg and 500 mg/kg rutin) were fed to juvenile tilapia for 56 days. Results revealed that supplementing with 100 mg/kg rutin enhanced growth, antioxidant capacity, and intestinal health in yellow catfish. However, the administration of rutin at a dosage of 500 mg/kg did not yield any additional advantages but potentially exhibited adverse effects on yellow catfish. This study has demonstrated the potential of rutin as a novel feed additive in aquafeed. This research aimed to examine the effects of dietary rutin supplementation on growth, body composition, serum biochemical indexes, liver enzyme activities and antioxidant-related genes expression, intestinal morphology, and microbiota composition of juvenile yellow catfish (Pelteobagrus fulvidraco). Rutin was added to the basal diets at doses of 0 (control), 100 mg/kg, and 500 mg/kg. Each diet was fed randomly into three tanks, each tank containing 30 fish with an initial body mass of (10.27 ± 0.62) g. The feeding trial was conducted in an indoor recirculating aquiculture system at 28 °C for 56 days. According to the findings, the inclusion of 100 mg/kg rutin significantly improved the growth performance of yellow catfish and reduced the feed conversion ratio; however, the growth promotion effect was diminished when the diet was supplemented with 500 mg/kg of rutin. The inclusion of 500 mg/kg rutin in the diet significantly reduced the level of crude lipid and protein of the whole fish. Serum activities of alkaline phosphatase, albumin, and total protein were all significantly increased when fish were fed the diet supplemented with 500 mg/kg rutin, while serum glucose was significantly lower compared to the control group. Meanwhile, dietary rutin at a concentration of 500 mg/kg significantly induced the hepatic mRNA expressions of antioxidant-related genes (including Cu/Zn-SOD, Mn-SOD, CAT, GPx) and inflammatory-associated genes (including TNFα, IL-10, LYZ). Incorporating rutin at doses of 100 mg/kg and 500 mg/kg into the diets resulted in a notable increase in superoxide dismutase (SOD) activity, while simultaneously reducing malondiadehyde (MDA) content in the liver and intestine. Intestinal villus height, villus width, muscular thickness, and lumen diameter were significantly increased with the administration of 500 mg/kg of dietary rutin. Gut microbial diversity analysis indicated that supplementing diets with 100 mg/kg and 500 mg/kg rutin significantly enhanced the abundance of Cetobacterium while decreasing Plesiomonas richness. In conclusion, dietary rutin levels at 100 mg/kg could enhance the growth, antioxidant capability, and intestinal health of yellow catfish under present experimental conditions. [ABSTRACT FROM AUTHOR]

Fat deposition and off-flavor in the muscle are the main problems affecting flesh quality in aquaculture fish, especially in catfish, leading to low acceptability and reduced market price. Yellow catfish is an important aquaculture fish in China. In this study, 40 days of depuration and starvation treatment were explored to improve the muscle quality of aquaculture yellow catfish. After depuration and starvation, the body weight, condition factor (CF) and mesenteric fat index (MFI) were all significantly decreased 20 days after treatment. The metabolomic profiles in muscle were characterized to analyze the muscle quality in yellow catfish. The results showed that the content of ADP, AMP, IMP, glutamic acid and taurine were significantly increased between 20 and 40 days post-treatment in the muscle of yellow catfish during the treatment, which was positively associated with the flesh tenderness and quality. In contrast, aldehydes and ketones associated with off-flavors and corticosterone associated with bitter taste were all decreased at 20 days post-treatment. Considering the balance of body weight loss and flesh quality improvement, depuration and starvation for around 20 days is suitable for aquaculture yellow catfish. Our study not only provides an effective method to improve the flesh quality of aquaculture yellow catfish but also reveals the potential mechanism in this process. [ABSTRACT FROM AUTHOR]

Intelectins (ITLNs) are a family of calcium-dependent lectins with carbohydrate-binding capacity, are distributed across various vertebrates, and play an important role in the innate immune response against pathogen infection. The yellow catfish Pelteobagrus fulvidraco (Siluriformes: Bagridae) is an economically important fish in China. The aim of this study was to quantify the gene expression of ITLN in response to pathogen-associated molecular patterns (PAMPs) stimulation. Here, the ITLN gene of P. fulvidraco was characterized and named PfITLN. The full-length cDNA of PfITLN was 1132 bp, including a 5'-untranslated region (UTR) of 140 bp, a 3'-UTR of 110 bp, and an open reading frame (ORF) of 882 bp encoding a polypeptide of 293 amino acids, which contains a signal peptide and two fibrinogen-related domains (FReDs). PfITLN had a molecular weight of 32.39 kDa with a theoretical pI of 5.03. The deduced PfITLN amino acid sequence had 81%, 64%, and 55% homology with Ictalurus furcatus, Danio rerio, and Homo sapiens, respectively. Moreover, the predicted tertiary protein structure of PfITLN was highly similar to that of other animals, and phylogenetic analysis showed that the PfITLN protein was close to those of other Teleostei. Real-time quantitative reverse transcription-PCR (qRT-PCR) analysis showed PfITLN expression in all examined tissues, with the highest abundance seen in the liver, followed by the head kidney, spleen, trunk kidney, and muscle. After PAMP infection with lipopolysaccharide (LPS) and polyriboinosinic polyribocytidylic acid (poly I:C), the expression levels of PfITLN were significantly upregulated at different time points. These results suggested that PfITLN might be involved in innate immunity. [ABSTRACT FROM AUTHOR]

Simple Summary: Myostatin is a negative regulator of muscle growth and development, and mutational inactivation of this gene increases muscle mass. Knockout of the mstnb gene in Pelteobagrus fulvidraco did not increase muscle mass, although our previous study of the mstna gene did. Instead, it reduced the body size and growth performance of Pelteobagrus fulvidraco. Through the present study, we found that the mutant Pelteobagrus fulvidraco had a reduction in the number of vertebrae, the length, and the intervertebral distance in Pelteobagrus fulvidraco, and these changes may be the underlying cause of the shorter body length in mutant Pelteobagrus fulvidraco. Histological comparison of the same sites in the mstn mutant and wild groups of Pelteobagrus fulvidraco also revealed that the number and density of osteocytes were greater in mstnb knockout Pelteobagrus fulvidraco than in wild-type Pelteobagrus fulvidraco. Based on obtaining mstnb gene knockout in Pelteobagrus fulvidraco, a study on the effect of the mstn gene on skeletal morphology and growth was performed by comparing the number and length of the vertebrae of mutant and wild-type fish in a sibling group of P. fulvidraco, combined with the differences in cells at the level of vertebral skeletal tissue. It was found that mstnb gene knockdown resulted in a reduction in the number of vertebrae, the length, and the intervertebral distance in P. fulvidraco, and these changes may be the underlying cause of the shorter body length in mutant P. fulvidraco. Further, histological comparison of the same sites in the mstn mutant and wild groups of P. fulvidraco also revealed that the number and density of osteocytes were greater in mstnb knockout P. fulvidraco than in wild-type P. fulvidraco. Our results demonstrated that when using genome editing technology to breed new lines, the effects of knockout need to be analyzed comprehensively and may have some unexpected effects due to insufficient study of the function of certain genes. [ABSTRACT FROM AUTHOR]

Nitrogen from ammonia is one of the most common pollutants toxics to aquatic species in aquatic environment. The intestinal mucosa is one of the key mucosal defenses of aquatic species, and the accumulation of ammonia nitrogen in water environment will cause irreversible damage to intestinal function. In this study, histology, immunohistochemistry, ultrastructural pathology, enzyme activity analysis and qRT-PCR were performed to reveal the toxic effect of ammonia nitrogen stress on the intestine of Pelteobagrus fulvidraco. According to histological findings, ammonia nitrogen stress caused structural damage to the intestine and reduced the number of mucous cells. Enzyme activity analysis revealed that the activity of bactericidal substances (Lysozyme, alkaline phosphatase, and ACP) had decreased. The ultrastructure revealed sparse and shortened microvilli as well as badly degraded tight junctions. Immunohistochemistry for ZO-1 demonstrated an impaired intestinal mucosal barrier. Furthermore, qRT-PCR revealed that tight junction related genes (ZO-1, Occludin, Claudin-1) were downregulated, while the pore-forming protein Claudin-2 was upregulated. Furthermore, as ammonia nitrogen concentration grew, so did the positive signal of Zap-70 (T/NK cell) and the expression of inflammation-related genes (TNF, IL-1β, IL-8, IL-10). In light of the above findings, we conclude that ammonia nitrogen stress damages intestinal mucosal barrier of Pelteobagrus fulvidraco and induces intestinal inflammation. [ABSTRACT FROM AUTHOR]

During the dam discharging period, the strong aeration of high-speed water leads to the supersaturation of total dissolved gas (TDG) in the downstream water, which causes gas bubble disease (GBD) in fish and threatens their survival. TDG supersaturation has now become an ecological and environmental issue of global concern; however, the molecular mechanism underlying the physiological effect of TDG supersaturation on fish is poorly known. Here, we comprehensively investigated the effect of TDG supersaturation on Pelteobagrus fulvidraco at the histopathological, biochemical, transcriptomic, and metabolomic levels. After exposure to 116% TDG, P. fulvidraco exhibited classic GBD symptoms and pathological changes in gills. The level of superoxide dismutase was highly significantly decreased. Transcriptomic results revealed that heat shock proteins (HSPs) and a large number of genes involved in immunity were increased by TDG stress. A key environmental sensor PI3K/Akt/mTOR pathway was significantly stimulated for defence against stress. Integrated transcriptomic and metabolomic analyses revealed that key metabolites and genes were upregulated in the triacylglycerol synthesis pathway and that amino acid levels decreased, which might be associated with TDG supersaturation stress. The present study demonstrated that TDG supersaturation could cause severe physiological damage in fish. HSP genes, immune functions, and energy metabolic pathways were enhanced to counteract the adverse effects. [ABSTRACT FROM AUTHOR]

In this study, we screened the expression stability of six reference genes (18S rRNA, β-actin, GAPDH, EF1a, B2M, and HPRT1) in hybrid yellow catfish (n = 6), considering the SBM levels, sampling time points, and different tissues. Four different statistical programs, BestKeeper, NormFinder, Genorm, and Delta Ct, combined with a method that comprehensively considered all results, were used to evaluate the expression stability of these reference genes systematically. The results showed that SBM levels significantly impacted the expression stability of most of the reference genes studied and that this impact was time-, dose-, and tissue-dependent. The expression stability of these six reference genes varied depending on tissue, sampling time point, and SBM dosage. Additionally, more variations were found among different tissues than among different SBM levels or sampling time points. Due to its high expression, 18S rRNA was excluded from the list of candidate reference genes. β-actin and GAPDH in the liver and β-actin, HPRT1 and EF1a in the intestine were the most stable reference genes when SBM levels were considered. HPRT1, and EF1a in tissues sampled at 2 W and EF1a and β-actin in tissues sampled at 4 and 6 W were proposed as two stable reference genes when different tissues were considered. When the sampling time points were considered, β-actin, EF1a, and HPRT1 were the top three stable reference genes in the intestine. In contrast, β-actin and B2M are the most stable reference genes in the liver. In summary, β-actin, EF1a, and HPRT1 were the more stable reference genes in this study. The stability of reference genes depends on the tissues, sampling time points, and SBM diet levels in hybrid yellow catfish. Therefore, attention should be paid to these factors before selecting suitable reference genes for normalizing the target genes. [ABSTRACT FROM AUTHOR]

The darkbarbel catfish (Pelteobagrus vachelli), an economically important aquaculture species in China, is extensively employed in hybrid yellow catfish production due to its superior growth rate. However, information on its genome has been limited, constraining further genetic studies and breeding programs. Leveraging the power of PacBio long-read sequencing and Hi-C technologies, we present a high-quality, chromosome-level genome assembly for the darkbarbel catfish. The resulting assembly spans 692.10 Mb, with an impressive 99.9% distribution over 26 chromosomes. The contig N50 and scaffold N50 are 13.30 Mb and 27.55 Mb, respectively. The genome is predicted to contain 22,109 protein-coding genes, with 96.1% having functional annotations. Repeat elements account for approximately 35.79% of the genomic landscape. The completeness of darkbarbel catfish genome assembly is highlighted by a BUSCO score of 99.07%. This high-quality genome assembly provides a critical resource for future hybrid catfish breeding, comparative genomics, and evolutionary studies in catfish and other related species. [ABSTRACT FROM AUTHOR]

Intensive culturing of hybrid yellow catfish (Pseudobagrus vachellii ♂ × Tachysurus fulvidraco ♀) has increased their mortality. Astragalus membranaceus has been used as an immune stimulant and antioxidant in fish for several years. A. membranaceus was decocted and mixed with the diet. After feeding for 28 d, the hybrid yellow catfish were challenged with Aeromonas hydrophila. To better understand the function of A. membranaceus in the defense of hybrid yellow catfish against A. hydrophila, we analyzed the spleen transcriptome data and relative percentage survival (RPS). There were 396 differentially expressed genes (DEGs) between the A. membranaceus and control groups at 24 h after A. hydrophila stimulation, including 263 upregulated and 133 downregulated DEGs. A significant enrichment of DEGs was found in the A. membranaceus group when the GO enrichment terms in the spleen were analyzed. The qRTPCRresults for the five upregulated and two downregulated DEGs from the spleen, intestine, and liver were consistent with the transcriptome data. The relative percentage survival of A. membranaceus was 85.71% after the fish were challenged with A. hydrophila. [ABSTRACT FROM AUTHOR]

Simple Summary: Enrofloxacin (EF) is an important antibiotic in global aquaculture. Due to the abuse and the emergence of drug resistance, the excess use of EF has occurred in recent years to result in residue exceeding in the edible tissues of aquatic animals. Withdrawal time (WT) is a red line to ensure food safety for humans. However, there is no related report of WT for EF in yellow catfish (Pelteobagrus fulvidraco). In addition to yellow catfish being sensitive to temperature, it can alter the disposition and elimination of EF and its main metabolite in fish bodies, ciprofloxacin (CF), thereby changing the WT in tissues. Therefore, we will conduct a WT estimation of EF in yellow catfish at different temperatures to establish related regulations to help residue surveillance in fish products. The objective of the present study was to investigate the residue depletion of EF and CF in yellow catfish to estimate its WTs in plasma and tissues after multiple oral doses for 3 days at 20 mg/kg at 15, 20, and 25 °C. Samples were collected at pre-designed time points after oral doses. A validated method was performed to quantify EF and CF in plasma and tissues by high-performance liquid chromatography. Statistical differences were conducted using one-way ANOVA analysis. According to the maximum residue limit of China and Europe considering 95% percentile with 95% confidence, the WTs were estimated to be 44, 72, 66, 99, and 95 days at 15 °C; 32, 66, 65, 86, and 73 days at 20 °C; and 32, 61, 64, 55, and 59 days at 25 °C in the plasma, muscle and skin, gill, liver, and kidney, respectively. We found that increased temperature shortened the WTs in plasma and tissues. Therefore, this study can help the risk assessment of EF in aquatic products for human health at different temperatures to avoid residue violation. [ABSTRACT FROM AUTHOR]

The experiment was conducted to investigate the effects of dietary leucine on growth, antioxidant capacity, immune response, and inflammation in juvenile yellow catfish. Five diets were formulated to contain five dietary leucine levels: 12.00 (control), 19.00, 26.00, 33.00, and 40.00 g kg−1. Each diet was randomly assigned to triplicate groups of 30 juvenile fish (5.02 ± 0.15 g) twice daily to apparent satiation for 56 days. Weight gain rate, specific growth rate, and activities of liver superoxide dismutase, glutathione peroxidase, and serum lysozyme, as well as immunoglobulin M content, significantly increased with increase in dietary leucine levels up to 26.00 g kg−1, but those values decreased significantly with a further increase in dietary leucine. On the contrary, the lowest malondialdehyde content was found in 26.00 and 33.00 g kg−1 leucine groups. The expression levels of IGF 1 and MYF 5 genes in muscle were significantly upregulated with increase in dietary leucine levels up to 26.00 g kg−1, but the expression of MSTN level showed the opposite trend. The lowest expression levels of IL 8 and TNFɑ genes in the liver were found in 26.00 g kg−1 leucine groups. The quadratic regression analysis on weight gain, specific growth rate, and feed conversion ratio against dietary leucine levels indicated that the optimal dietary leucine requirement was estimated to be 26.84–27.00 g kg−1of the dry diet. [ABSTRACT FROM AUTHOR]

The Bagridae fish family holds significant economic value and enjoys a high demand in the commercial market due to its desirable characteristics, such as delicious meat, fewer muscle spines, and a pleasing flavor. In recent years, the Bagridae has experienced rapid development in the seed industry in response to industry demands. Researchers have conducted extensive studies on genetic breeding in the Bagridae, employing a comprehensive breeding approach that combines conventional breeding techniques with innovative new technologies and cooperative efforts. In this review, we present an overview of the market situation and discuss various breeding processes applied to the Bagridae, including selective breeding, genetic engineering breeding, cell engineering breeding, molecular marker-assisted breeding, and hybrid breeding. Additionally, we focus on introducing the cultivation methods for two new Bagridae varieties. Furthermore, we explore and summarize the breeding conditions, genetic background, heterosis, comprehensive breeding technology, stress resistance, and metabolic nutrition of hybrid Bagridae catfishes. Overall, noticeable heterosis has been observed in the breeding of the hybrid yellow catfish "Huangyou-1", which exhibits promising market prospects and economic benefits for aquaculture. Our study aims to underscore the importance of harnessing the heterosis of catfish, particularly the Pelteobagrus and Bagridae species. Consequently, this review provides an update on the current available information regarding the seed industry of the Bagridae fish family. [ABSTRACT FROM AUTHOR]

To assess the effect of dietary selenium (Se) sources on the meat quality and antioxidant capacity of yellow catfish (Pelteobagrus fulvidraco), sodium selenite (Na2SeO3), Se yeast, and selenium-enriched Spirulina platensis (Se–SP) were supplemented in the control diet at 0.30 mg Se/kg feed to formulate four diets. The experimental period lasted 50 days. The results showed that Se levels in the plasma, liver, muscle, and whole body were significantly increased by dietary Se yeast supplementation (P < 0.05) but showed no change in response to Na2SeO3 (P > 0.05). The three types of Se all increased the firmness and decreased the fracturability of the muscles (P < 0.05), but only Na2SeO3 resulted in higher springiness, flexibility, stringiness, and stickiness (P < 0.05). In addition, the muscle n−3 polyunsaturated fatty acid (PUFA) content was increased by Se yeast (P < 0.05). Regarding antioxidant capacity, dietary Se yeast and Se–SP supplementation improved hepatic glutathione peroxidase activity but decreased hepatic malondialdehyde content (P < 0.05). Given these results, Se yeast was found to be the optimal source of Se for yellow catfish for higher tissue retention, antioxidant capacity, and PUFA levels. Dietary Se is an effective way to regulate the meat quality and antioxidant capacity of yellow catfish. [ABSTRACT FROM AUTHOR]

The hemorrhagic disease has become a major bottleneck in yellow catfish Pelteobagrus fulvidraco aquaculture. Yet scarce information is available on Bacillus subtilis as a pathogen of hemorrhagic disease in cultured yellow catfish. In this study, a virulent isolate, temporarily named HS5, was isolated from hemorrhagic disease-infected cultured yellow catfish, and was identified phenotypically and molecularly as B. subtilis. In addition, isolate HS5 showed an LD50 value of 5.20×106 CFU/ml in yellow catfish, exhibited beta-haemolytic activity, harbored the virulent entFM gene, and displayed high susceptibility to enrofloxacin and florfenicol in aquaculture use. To the best of our knowledge, this is the first report of B. subtilis as a pathogen of hemorrhagic disease in farmed yellow catfish. [ABSTRACT FROM AUTHOR]

Introduction: The pathogenesis of Vibrio mimicus infection in yellow catfish (Pelteobagrus fulvidraco) remains poorly understood, particularly regarding the impact of infection with the pathogen on primary target organs such as the skin and muscle. Methods: In this study, we aim to analyze the pathological intricacies of the skin and muscle of yellow catfish after being infected with V. mimicus using a 1/10 LC50 seven-day post-infection model. Furthermore, we have utilized integrated bioinformatics to comprehensively elucidate the regulatory mechanisms and identify the key regulatory genes implicated in this phenomenon. Results: Our histopathological examination revealed significant pathological changes in the skin and muscle, characterized by necrosis and inflammation. Moreover, tissue remodeling occurred, with perimysium degeneration and lesion invasion into the muscle along the endomysium, accompanied by a transformation of type I collagen into a mixture of type I and type III collagens in the perimysium and muscle bundles. Our eukaryotic transcriptomic and 4D label-free analyses demonstrated a predominantly immune pathway response in both the skin and muscle, with downregulation observed in several cell signaling pathways that focused on focal adhesion-dominated cell signaling pathways. The upregulated genes included interleukins (IL)-1 and -6, chemokines, and matrix metallopeptidases (mmp)-9 and -13, while several genes were significantly downregulated, including col1a and col1a1a. Further analysis revealed that these pathways were differentially regulated, with mmp-9 and mmp-13 acting as the potential core regulators of cytokine and tissue remodeling pathways. Upregulation of NF-kB1 and FOSL-1 induced by IL-17C and Nox 1/2-based NADPH oxidase may have held matrix metallopeptidase and cytokine-related genes. Also, we confirmed these relevant regulatory pathways by qPCR and ELISA in expanded samples. Discussion: Our findings unequivocally illustrate the occurrence of a cytokine storm and tissue remodeling, mediated by interleukins, chemokines, and MMPs, in the surface of yellow catfish infected with V. mimicus. Additionally, we unveil the potential bidirectional regulatory role of MMP-9 and MMP-13. These results provide novel perspectives on the intricate immune response to V. mimicus infection in yellow catfish and highlight potential targets for developing therapies. [ABSTRACT FROM AUTHOR]

Simple Summary: Enrofloxacin (EF) is a commonly used broad-spectrum antibiotic in aquaculture against Gram-negative and Gram-positive bacteria. Ciprofloxacin (CF) has similar antibacterial activities to EF and has been developed as an aquatic medicine. It is well known that only the free concentration of a drug is effective for killing challenging pathogens. Hence, the plasma protein binding ratio (PPBR) of drugs is an important parameter in clinical medicine. Although PPBRs of EF and CF have been reported in several livestock animals, little information is available on aquatic animals. Moreover, environmental temperatures may influence the PPBR of drugs used for aquatic animals. Therefore, this study investigates PPBRs of EF and CF in the plasma of several finfish species such as yellow catfish (Pelteobagrus fulvidraco), grass carp (Ctenopharyngodon idella), and largemouth bass (Micropterus salmoides) at different concentrations with different temperatures. The present study facilitates the design of therapeutic regimens of EF for different aquatic animals at different concentrations. The objective of this study was to investigate the PPBRs of EF and CF in the plasma of yellow catfish, grass carp, and largemouth bass at different temperatures with different concentrations. A fast and simple ultrafiltration method was used to determine the PPBRs of EF and CF. Results showed that PPBRs of EF decreased from 37.71% to 9.66%, from 46.10% to 13.52%, and from 43.90% to 4.36% in the plasma of yellow catfish with the increase of concentration from 15 to 25 °C. The same trends of PPBRs of EF were presented in the plasma of grass carp and largemouth bass. In comparison to the data at the same concentration of EF at disparate temperatures, the PPBRs of EF at a concentration of 1 µg/mL increased from 37.71% to 46.10% and then decreased to 43.90% in the plasma of yellow catfish with elevated temperature from 15 to 25 °C. There is no obvious regularity with the rise of temperature, and the same phenomenon also were found in other concentrations and species. Meanwhile, the PPBRs of CF also decreased in the three species with the rise in concentration. Under the consistent concentration, the temperature-dependent regularities were not found in the PPBRs of CF. Overall, the increased concentration reduced the PPBRs of EF and CF in the plasma of three fish species, and the alteration in temperature only has a certain effect on the PPBRs of EF and CF. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the potential adverse effects of the practical application of copper sulfate on yellow catfish (Pelteobagrus fulvidraco) and to provide insights into the gill toxicity induced by copper sulphate. Yellow catfish were exposed to a conventional anthelmintic concentration of copper sulphate (0.7 mg/L) for seven days. Oxidative stress biomarkers, transcriptome, and external microbiota of gills were examined using enzymatic assays, RNA-sequencing, and 16S rDNA analysis, respectively. Copper sulphate exposure led to oxidative stress and immunosuppression in the gills, with increased levels of oxidative stress biomarkers and altered expression of immune-related differentially expressed genes (DEGs), such as IL-1β, IL4Rα, and CCL24. Key pathways involved in the response included cytokine–cytokine receptor interaction, NOD-like receptor signaling pathway, and Toll-like receptor signaling pathway. The 16S rDNA analysis revealed copper sulphate altered the diversity and composition of gill microbiota, as evidenced by a significant decrease in the abundance of Bacteroidotas and Bdellovibrionota and a significant increase in the abundance of Proteobacteria. Notably, a substantial 8.5-fold increase in the abundance of Plesiomonas was also observed at the genus level. Our findings demonstrated that copper sulphate induced oxidative stress, immunosuppression, and gill microflora dysbiosis in yellow catfish. These findings highlight the need for sustainable management practices and alternative therapeutic strategies in the aquaculture industry to mitigate the adverse effects of copper sulphate on fish and other aquatic organisms. [ABSTRACT FROM AUTHOR]

Introduction: Ammonia has been of concern for its high toxicity to animals. Ncarbamylglutamate (NCG) can reduce blood ammonia levels in mammals, but studies on ammonia tolerance in fish are insufficient. Methods: Juvenile yellow catfish were fed two levels of NCG (0.00% and 0.05%) for 84 days under three ammonia levels (0.00, 0.08, and 0.16 mg/L NH3). Results and Discussion: The results showed that survival rate (SUR), final body weight (FBW), weight gain (WG), and serum total protein (TP), triglycerides (TG), glucose (Glu), ornithine (Orn), citrulline (Cit) contents, and liver superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), arginase (ARG), ornithine transcarbamylase (OTC) activities decreased with the increase of ammonia levels, on the contrary, feed conversion ratio (FCR), hepatosomatic index (HSI), and serum ammonia, urea, alanine aminotransferase (ALT), aspartate aminotransferase (AST), glutamine (Gln), arginine (Arg) contents, and liver malondialdehyde (MDA), tumor necrosis factor (TNF), interleukin (IL) 1, IL 8 contents, and mRNA expressions of cu/zn sod, cat, gpx, gr, tnf ɑ, il 1, and il 8 were significantly increased. Dietary 0.05% NCG supplementation had higher SUR, FBW, WG, feed intake (FI), whole-body protein, and serum TP, total cholesterol (TC), Glu, citrulline (Cit) contents, and liver SOD, GPx, argininosuccinate synthetase (ASS), argininosuccinate lyase (ASL), inducible nitric oxide synthase (iNOS) activities compared to 0.00% NCG group, but had lower serum ammonia, urea, ALT, AST, Gln, Arg contents, and liver MDA, TNF, IL 1, IL 8 contents, and neuronal nitric oxide synthase activity. At the end of bacterial challenge, cumulative mortality (CM) increased with ammonia levels increased, but serum antibody titer (AT), lysozyme (LYZ) activity, 50% hemolytic complement, immunoglobulin (Ig) contents, respiratory burst (RB), phagocytic indices decreased with ammonia levels increased. CM in 0.05% NCG group was lower than that in 0.00% NCG group, but serum AT, LYZ activity, Ig content, RB in 0.05% NCG group were significantly higher. The correlation analysis found that iNOS was positively correlated with ASS activity. This study indicates that dietary NCG supplementation can improve the ammonia tolerance of yellow catfish, and ASS may also be the target of NCG to activate the urea cycle. [ABSTRACT FROM AUTHOR]

This study is aimed at evaluating the effects of dietary protein-to-energy ratios on the growth, immunological response, antioxidative capacity, liver and intestinal histology, and growth-related gene expression of hybrid yellow catfish (Pelteobagrus fulvidraco ♀ × Pelteobagrus vachelli ♂). Eight diets were formulated to form different protein/energy ratios of 84, 88, 90, 93, 95, 96, 99, and 103 mg/kcal (P/E84, P/E88, P/E90, P/E93, P/E95, P/E96, P/E99, and P/E103), respectively. These diets contain different levels of gross energy (GE), ranging from 4.13 to 4.76 kcal g-1. Seven hundred and twenty healthy fish (17.15 ± 0.02 g) were randomly dispersed into 24 rectangular fiberglass tanks with 8 treatments in triplicate groups. The fish fed a P/E ratio of 95 mg/kcal demonstrated the best growth and feed utilization. A significant (P < 0.05) increase in percent weight gain (WG%) and specific growth rate (SGR) was seen as the dietary P/E ratio ameliorated from P/E84 to P/E95, followed by a decreased pattern in these parameters. Feed conversion ratio (FCR) and daily feed intake (DFI) were significantly impacted by dietary P/E ratios (P < 0.05). Additionally, an optimum P/E ratio improved intestinal morphology. However, low or high P/E ratio diets can cause oxidative stress, impaired liver function, and significantly reduced nonspecific immunity. The expression of target of rapamycin (TOR) and insulin-like growth factor-1 (IGF1) genes in the liver was considerably influenced by dietary protein-to-energy ratios (P < 0.05). Based on the statistical analysis of WG% against the dietary P/E ratio, the optimal P/E ratio for the studied species was estimated to be 92.92 mg/kcal. [ABSTRACT FROM AUTHOR]

Freshwater aquaculture is an important source of greenhouse gas (GHG) emissions. GHG emissions are expected to lead to global warming and climate change. A reduction in GHG emissions is urgently required for the sustainable development of freshwater aquaculture. In this study, a laboratory-scale experiment was conducted to analyze the effects of a vegetable–fish co-culture on CH4 and N2O emissions from a freshwater aquaculture pond. The results show that the co-culturing of yellow catfish with pak choi (PC-F) or water spinach (WS-F) significantly reduced the N2O emission from the aquaculture pond by 60.20% and 67.71%, respectively, as compared with a yellow catfish monoculture (F). However, the co-culture of these two vegetables did not affect the level of CH4 emissions. The reduction in N2O emissions was primarily attributed to the decrease in the concentration of N2O and NO3− in the water. The overall global warming potential (GWP) of CH4 and N2O was significantly reduced by 19.1% with PC-F compared to F, but it did not significantly differ between WS-F and F. PC and WS cultivation improved the food yield by 1555.52% and 419.95% compared to F, respectively. Consequently, the GHG emissions intensity (GHGI) under PC-F and WS-F decreased by 96.15% and 80.77% compared to F, respectively. Altogether, the results highlight that a vegetable–fish co-culture is likely an efficient system for mitigating GWP per unit of food yield in freshwater aquaculture ponds. These results can provide a reference for the mitigation of GHG emissions from freshwater aquaculture. [ABSTRACT FROM AUTHOR]

The yellow catfish (Pelteobagrus fulvidraco) is an economic fish with a large breeding scale, and diseases have led to huge economic losses. Tumor necrosis factor receptor-associated factors (TRAFs) are a class of intracellular signal transduction proteins that play an important role in innate and adaptive immune responses by mediating NF-κB, JNK and MAPK signaling pathways. However, there are few studies on the TRAF gene family in yellow catfish. In this study, the open reading frame (ORF) sequences of TRAF1, TRAF2a, TRAF2b, TRAF3, TRAF4a, TRAF4b, TRAF5, TRAF6 and TRAF7 genes were cloned and identified in yellow catfish. The ORF sequences of the nine TRAF genes of yellow catfish (Pf_TRAF1-7) were 1413–2025 bp in length and encoded 470–674 amino acids. The predicted protein structures of Pf_TRAFs have typically conserved domains compared to mammals. The phylogenetic relationships showed that TRAF genes are conserved during evolution. Gene structure, motifs and syntenic analyses of TRAF genes showed that the exon–intron structure and conserved motifs of TRAF genes are diverse among seven vertebrate species, and the TRAF gene family is relatively conserved evolutionarily. Among them, TRAF1 is more closely related to TRAF2a and TRAF2b, and they may have evolved from a common ancestor. TRAF7 is quite different and distantly related to other TRAFs. Real-time quantitative PCR (qRT-PCR) results showed that all nine Pf_TRAF genes were constitutively expressed in 12 tissues of healthy yellow catfish, with higher mRNA expression levels in the gonad, spleen, brain and gill. After infection with Edwardsiella ictaluri, the expression levels of nine Pf_TRAF mRNAs were significantly changed in the head kidney, spleen, gill and brain tissues of yellow catfish, of which four genes were down-regulated and one gene was up-regulated in the head kidney; four genes were up-regulated and four genes were down-regulated in the spleen; two genes were down-regulated, one gene was up-regulated, and one gene was up-regulated and then down-regulated in the gill; one gene was up-regulated, one gene was down-regulated, and four genes were down-regulated and then up-regulated in the brain. These results indicate that Pf_TRAF genes might be involved in the immune response against bacterial infection. Subcellular localization results showed that all nine Pf_TRAFs were found localized in the cytoplasm, and Pf_TRAF2a, Pf_TRAF3 and Pf_TRAF4a could also be localized in the nucleus, uncovering that the subcellular localization of TRAF protein may be closely related to its structure and function in cellular mechanism. The results of this study suggest that the Pf_TRAF gene family plays important roles in the immune response against pathogen invasion and will provide basic information to further understand the roles of TRAF gene against bacterial infection in yellow catfish. [ABSTRACT FROM AUTHOR]