Elevated mortality rates and growth suppression of large yellow croaker (Larimichthys crocea) under prolonged high summer temperatures present significant challenges for sustainable aquaculture. In response to these thermal stress pressures, this study investigates the effects of dietary inulin supplementation on the resilience and growth performance of juvenile large yellow croaker. Over a two-month period (July 14 to September 14), fish were acclimated and assigned to five diet groups containing 0 %, 0.1 %, 0.2 %, 0.4 %, and 0.8 % inulin. Using a multi-omics approach (transcriptomic, metabolomic, and microbiomic changes) in liver and gut tissues, we assessed the effect of inulin in Larimichthys crocea. Results demonstrated that an optimal inulin level (0.4 %) significantly improved growth performance. Transcriptomic data revealed upregulation of genes involved in energy metabolism pathways such as glycolysis and fatty acid biosynthesis, alongside downregulation of immune and stress-related genes. Metabolomic profiles showed increased metabolites related to energy production and lipid metabolism. Gut microbiome analysis indicated a reduction in overall diversity but enrichment of beneficial bacteria, including Lactobacillus, which correlated with higher levels of health-promoting short-chain fatty acids and amino acids. Integrated analyses highlighted strong associations between key microbial taxa and metabolic pathways supporting nutrient absorption and vitamin synthesis. These findings suggest that dietary inulin enhances thermal stress tolerance by modulating metabolism and gut microbiota, offering a promising nutritional strategy to improve large yellow croaker aquaculture under change-induced heat stress.

The yellow body coloration of large yellow croaker (Larimichthys crocea) constitutes a crucial economic trait, yet its underlying genetic regulatory mechanisms remain poorly understood. This study systematically elucidated the molecular basis of body color variation by integrating genome resequencing and skin transcriptome analyses, combined with the contextual analysis of key pigmentation-related genes and phenotypic histological validation. 200 phenotyped individuals (including yellow-selected lines, F1 progeny, and normal control groups, all derived from a well-characterized aquaculture stock) identified 39 significantly associated SNPs (-log₁₀(P) ≥ 6), mapping to multiple candidate genes. These genes were significantly enriched in pathways related to pigment deposition (GO:0033059), melanosome organization (GO:0032438), melanogenesis, and tyrosine metabolism. Cross-developmental stage transcriptome analysis revealed 2395 differentially expressed genes (DEGs). Multi-omics integration identified eight overlapping candidate genes, including tyrp1, slc45a2, oca2, and dgat2, among which tyrp1 was prioritized for in-depth validation based on its core regulatory role in eumelanin synthesis, significant SNP association signal, and consistent downregulation in transcriptomic data. Experimental validation demonstrated that the g.895C > T mutation in exon 2 of tyrp1b was strongly significantly associated with the yellow phenotype: the frequency of mutant genotypes (TT/CT) reached 92.86%in the yellow-selected group, whereas the control group exclusively exhibited the wild-type genotype (CC). qPCR confirmed significantly downregulated tyrp1b expression in the skin of yellow individuals, consistent with the transcriptome trend. Histological and stereomicroscopic observations of skin tissues further validated the physiological basis of the yellow phenotype, revealing a significant reduction in melanophore number and abnormal melanosome morphology in yellow-phenotype individuals, accompanied by increased xanthophore density. These results suggest that tyrp1b mutation is strongly associated with the yellow phenotype. However, the presence of a wild-type CC individual in the yellow group indicates that this mutation is not strictly required for yellow coloration, suggesting that other genetic or environmental factors may also contribute to the phenotype, Additionally, downregulation of the carotenoid metabolism gene bco2 coupled with upregulation of xdh, together with the functional changes of slc45a2 and oca2, may synergistically promote xanthophore pigment deposition, contributing to the yellow phenotype. As melanin synthesis in large yellow croaker relies on the conserved tyrosinase pathway and transporter proteins, mutations in associated genes (tyrp1b, slc45a2, oca2) represent a primary underlying cause for the loss of melanin-based coloration and transition to a yellow phenotype in L. crocea. These findings provide key molecular targets and a theoretical foundation for molecular breeding of body color in this species, and also enrich the understanding of xanthism regulatory mechanisms in teleosts.

The monosex culture of all-male populations in large yellow croaker (Larimichthys crocea) offers numerous advantages, including simplifying management and enhancing profitability and sustainability in aquaculture. In fish with an XX-XY sex determination system, inducing neofemales and subsequently producing YY supermales are crucial steps in establishing all-male populations for aquaculture. In this study, we systematically investigated the optimal treatment for inducing sex reversal by administering different concentrations (0.2, 1, and 5 mg/kg) of 17 beta-estradiol (E-2), and evaluated the sex reversal, growth, survival, antioxidant capacity, gonadal development, and the expression of sex-related genes in large yellow croaker. Neofemales were successfully induced across all E-2-treated groups, with complete sex reversal (100 %) observed in XY individuals exposed to 1 and 5 mg/kg E-2, whereas partial reversal (40-60 %) occurred in the 0.2 mg/kg group. However, as the concentration of E-2 exposure increased, the treatment groups exhibited a trend of decreased growth performance, reduced survival rates, and elevated antioxidant enzyme activities. These findings suggested that the optimal concentration for inducing sex reversal was 1 mg/kg E-2 administered over an 80-day period from 45 to 125 dph (days post-hatching). Furthermore, the gonad development was examined in the neofemales in successive 15 months. At 9 mph (months post-hatching), the neofemales induced by 1 mg/kg E-2 oral administration exhibited peri-nucleolus oocytes, and the expression patterns of the sex-related genes dmrt1 and cyp19a1a were similar to those observed in normal females. After maturation, neofemales were crossed with normal males (XY), and genotypic analysis of the resulting offspring using sex-specific molecular markers confirmed that the proportion of YY supermales conformed to Mendelian inheritance. Additionally, YY supermales exhibited comparable growth and gonadal development to normal males at 120 dph. Taken together, we have established an efficient method for inducing male-to-female sex reversal and breeding YY supermales in large yellow croakers, providing a solid foundation for the production of all-male populations.

The large yellow croaker (Larimichthys crocea) is a critical mariculture species in China that frequently suffers significant outbreaks of Cryptocaryon irritans infections, especially in warm months, leading to severe economic losses. We investigated the therapeutic effects of florfenicol (FFC) against C. irritans in large yellow croaker, focusing on survival outcomes, antioxidant capacity and immune mechanisms through transcriptomic and metabolomic approaches. FFC supplementation at 0.75 g/kg significantly improved survival rates (57.9

Body color is an important economic trait of large yellow croaker (Larimichthys crocea), but the pigment development and migration processes during its early development is poorly understood. This study summarized the critical developmental stages and the formation and developmental dynamics of major pigment cells, including xanthophores, melanophores, and iridophores, in a total of 1890 samples ranging from newly hatched larvae (0 days post-hatch, dph) to 182 dph juveniles through microscopic observation, cryosection, and image acquisition. In addition, the phenomenon of yellow coloration fading is prevalent in cultured L. crocea. However, a small number of individuals in both natural and farmed populations maintain stable yellow body coloration. This study utilized F-3-generation (selected through multigenerational selective breeding for superior yellow coloration intensity and growth performance traits) as the experimental group (designated as yellow group), with offspring from regular cultured populations serving as the control group for comparison. The results demonstrated that the yellow group showed significantly higher xanthophore counts within embryonic oil globules (p < 0.05) and significantly larger abdominal xanthophore coverage areas during the juvenile stage (p < 0.05) than the control group. This study provided data for the precise research of pigment and provided feasibility support for the selective breeding of its body color in L. crocea.

GPR97, a member of the adhesion G protein-coupled receptor (aGPCR) family, functions as a membrane receptor for glucocorticoids, mediating their rapid non-genomic effects and immune regulation in mammals. However, the membrane receptor for glucocorticoids in fish and the mechanisms underlying cortisol's rapid responses remain poorly understood. In this study, GPR97 was cloned and characterized from the large yellow croaker (Larimichthys crocea) as LcGPR97. Sequence alignment and membrane localization analyses confirmed its classification within the aGPCR family. Upon cortisol stimulation in HEK293 cells expressing LcGPR97, intracellular cAMP levels decreased, Ca2+ concentration increased, and ERK1/2 phosphorylation was activated. These results suggest that cortisol activates LcGPR97, which couples with Gαi/o proteins to mediate downstream signaling. Furthermore, LcGPR97 was highly expressed in immune-related tissues, including the spleen, trunk kidney and head kidney, and its expression increased after lipopolysaccharide (LPS) stimulation, indicating its role in immune modulation during inflammation. These findings offer novel insights into the molecular mechanisms of cortisol's rapid effects via membrane receptors in fish and highlight potential implications for immune regulation in aquaculture.

Large yellow croaker is the most widely farmed marine fish in China, yet cold surges often result in high mortality, causing substantial economic losses, particularly to aquaculture in Zhejiang Province. Our previous studies demonstrated that cold pretreatment enhances cold tolerance in large yellow croaker; however, it remains unclear whether this enhanced resilience persists during the recovery phase. In this study, large yellow croaker were subjected to cold pretreatment followed by a two-week recovery period before being exposed to acute cold stress. Subsequent physiological, histological, ultrastructural, and molecular analyses were conducted. The results revealed that fish retained cold resilience after the recovery phase. The gill tissue was identified as the most sensitive organ during early stages of cold stress as evidenced by a significant increase in apoptotic cells. However, cold pretreatment effectively mitigated gill damage by promoting mitochondrial fusion and enhancing antioxidant capacity. This was achieved through the upregulation of mitochondrial fusion and antioxidantrelated genes, as well as downregulation of mitochondrial fission genes. Transcriptomic profiling further identified 18 differentially expressed genes after recovery from cold pretreatment. These genes were associated with immune response, antioxidant defense, apoptotic signaling, transcriptional regulation, mitochondrial function, and circadian regulation. In conclusion, these findings confirm that cold pretreatment induces sustained cold tolerance in large yellow croaker and provides insights into the molecular mechanisms underlying this resilience, providing practical strategies to mitigate losses caused by cold surges in aquaculture.

Research shows that natural starvation during cold months may enhance the croaker's cold tolerance, yet the high mortality rates persist, indicating that factors like water velocity may also play a critical role. This study investigates how low temperature, starvation and water velocities affect the croaker's survival, focusing on antioxidant capacity, metabolic, transcriptomic and microbiota changes, aiming to improve management strategies for this economically important species in aquaculture. 400 large yellow croakers were divided into fed and starved groups to assess cold tolerance under gradually decreasing temperatures, and swimming endurance under increased water velocities up to 0.35 m/s. The fish were subsequently subjected to simulated overwintering in controlled flow conditions at different velocities to observe survival rates. Samples from the fish, including liver and intestines, were collected for antioxidant capacity, transcriptomic, metabolomic and microbiota analyses. Our results demonstrate that starvation enhances cold tolerance in large yellow croakers, but reduces swimming endurance significantly, suggesting a complex interplay between metabolic preservation and physical capability. Transcriptomic analyses revealed a significant shift towards fatty acid oxidation and down-regulation of steroid biosynthesis pathways, particularly under combined stress conditions. Moreover, the excessive up-regulation of lipid metabolism led to the accelerated production of ROS, resulting in oxidative stress in large yellow croaker. Both liver metabolomics and intestinal microbiota composition studies illustrated significant alterations in metabolic profiles. These findings provide insights into how environmental stressors impact the physiological and metabolic dynamics of the large yellow croaker, offering potential strategies for improving resilience and survival in aquaculture settings.

People commonly consume large yellow croaker with skin, yet comprehensive studies on the skin's nutritional value, flavor, and health risks are lacking. The skin from wild fish and those from five main farming areas, nearly representing all fish in the market, were analyzed. The study revealed that the skin of all tested fish exhibited high levels of carotenoids, EPA, DHA, Σn-3/Σn-6 PUFA, Fe, Se, Cu, Zn, and various flavor compounds including free amino acids, 5′-nucleotides, and odor substances, and low levels of atherosclerotic and thrombogenic indices, suggesting health benefits. Notably, the wild fish skin was yellower with high carotenoid accumulation and nutritionally superior in fatty acids but showed a high heavy metal risk. Additionally, this research has, for the first time, elucidated that carotenoid storage in the skin of large yellow croaker depends on lutein esterification with oleic, palmitic, and decanoic acids. In summary, the current study indicates that the skin of farmed fish offers significant nutritional value and favorable flavor profiles, making it safe for consumption. However, while the skin of wild large yellow croaker is more nutritionally advantageous, it also presents a non-negligible risk of heavy metal contamination.

This study investigated the effects of a fulvic acid–based functional feed material (FBFM)—a mixture of fulvic acid and a Clostridium butyricum fermented suspension—on the growth performance and physiological adaptation of large yellow croaker (Larimichthys crocea) exposed to summer heat stress, using a multi-omics strategy. Fish were fed diets containing different concentrations of FBFM for 60 days and assessed for growth performance, antioxidant status, hepatic gene expression, liver and intestinal metabolism, and gut microbiota composition. Results showed that the group receiving 1.5 g/kg FBFM (FBFM3) exhibited the highest average weight gain, survival rate, and specific growth rate, along with significantly enhanced activities of antioxidant enzymes (CAT, SOD, GSH-Px, T-AOC) in both the liver and the intestine. Transcriptomic profiling of the FBFM3 group revealed significant upregulation of genes involved in the TCA cycle and oxidative phosphorylation pathways, while metabolomic analysis indicated increased levels of short-chain fatty acids and metabolites associated with bile acid biosynthesis. FBFM supplementation also promoted the enrichment of beneficial gut microbiota, notably Firmicutes and Proteobacteria, although overall α-diversity decreased. These findings demonstrate that dietary FBFM supplementation improves heat stress resilience in large yellow croaker by enhancing antioxidant capacity, optimizing energy metabolism, and modulating gut microbiota. This work highlights the potential of FBFM as a nutritional strategy to promote growth and health of marine fish under environmental stress.

To elucidate the physiological and molecular mechanisms underlying cold tolerance in the mangrove species Kandelia obovata Sheue & al, this study measured the antioxidant enzyme activities and photosynthetic pigment contents of two populations-cold-tolerant and -sensitive-under natural overwintering conditions. In addition, transcriptome sequencing was performed to analyze differentially expressed genes (DEGs), transcription factor families, single nucleotide polymorphisms (SNPs), and alternative splicing events. The results showed that catalase activity was significantly elevated in the cold-tolerant population, which enhanced the efficiency of hydrogen peroxide scavenging. In contrast, although the superoxide dismutase activity was relatively high in the cold-sensitive population, its downstream scavenging capacity was insufficient, resulting in an overall lower antioxidant efficiency. The KEGG enrichment analysis indicated that pathways such as phenylpropanoid biosynthesis, amino sugar metabolism, and plant hormone signal transduction might be involved in the response to low-temperature stress. Further analysis revealed that transcription factors such as WRKY, NAC, MYB, and ERF were differentially expressed at significant levels in the cold-tolerant population, suggesting that they may play important roles in low-temperature adaptation. In addition, the diversity of SNPs and alternative splicing events may enhance protein function and contribute to improved cold tolerance. In summary, the cold-tolerant K. obovata population achieves low-temperature tolerance through multiple mechanisms, including antioxidant defense, metabolic regulation, and transcriptional as well as post-transcriptional regulation. This study provides a theoretical basis for elucidating the molecular foundations of cold tolerance in K. obovata.

Large yellow croaker is one of the most important marine aquaculture species in China. However, due to its intolerance to low temperatures, overwintering often results in deaths, causing significant economic losses. In a controlled laboratory experiment, we assessed the impact of temperature and water current on the overwintering behavior of large yellow croaker using a swimming flume. The experiment was divided into two temperature conditions (8 degrees C and 20 degrees C) and four flow rates (15 cm/s, 20 cm/s, 25 cm/s, and 30 cm/s). We measured sustained swimming time, tail beat frequency, opercular respiratory rate, and conducted transcriptomic and metabolomic analyses. Our findings indicate that lower temperatures and higher flow rates reduce sustained swimming time. Flow rate had a more significant impact on tail beat frequency than temperature, whereas respiratory rate was more affected by temperature than flow rate. Omics data revealed that the ABC transporter, glycolysis and oxidative phosphorylation pathways were downregulated, whereas the citrate cycle pathway was upregulated, suggesting a metabolic adjustment to optimize ATP production and cellular transport mechanisms for efficient energy utilization and metabolic homeostasis. This study concludes that colder temperatures compromise metabolic efficiency and increase energetic demands, leading to fatigue and diminished endurance. Large yellow croakers adapt to cold temperatures by relying more on the citrate cycle and less on glycolysis and oxidative phosphorylation for energy. These findings offer a scientific basis for developing more resilient aquaculture systems that can better support the overwintering survival and overall health of large yellow croaker, thereby contributing to more sustainable and productive aquaculture operations.

This study employed a multi-omics approach—integrating transcriptomics, metabolomics, and gut microbiota analysis—to investigate the effects of dietary sodium butyrate (SB; 0, 0.05

With the continuous development of China's shipbuilding and maritime industries, increasing amounts of volatile polycyclic aromatic hydrocarbons (PAHs) are being released into marine ecosystems, posing serious ecological and health risks to marine organisms. As one of the most important mariculture species in China, the large yellow croaker is highly vulnerable to PAHs exposure, with aquaculture production reaching 280,997 tons in 2024. Studies have shown significant bioaccumulation of PAHs in nearshore-farmed large yellow croaker, with concentrations in both ambient water and muscle tissue approximately 3.6 times higher than those in far sea (FS) environments. Multi-omics analyses revealed that PAHs exposure suppressed the PPAR signaling pathway in the liver, disrupting lipid metabolism regulation. However, the upregulation of fatty acid β-oxidation represents a compensatory dysregulation process, leading to adverse effects such as excessive generation of reactive oxygen species (ROS), lipid peroxidation, and inflammatory responses. Concurrently, intestinal metabolomics identified depletion of glutathione, resulting in a several-fold increase in CYP450-mediated toxic intermediates. These metabolites further induced gut microbiota dysbiosis, characterized by reduced abundance of beneficial bacterial phyla. Collectively, these effects contribute to systemic oxidative stress, manifested as decreased antioxidant enzyme activities and elevated levels of ROS and malondialdehyde (MDA). These findings elucidate a ''metabolic disorder-detoxification paralysis'' cascade, whereby PAHs disrupt redox homeostasis via interactions along the hepatointestinal axis. This study provides critical insights into species-specific responses to environmental pollutants and strongly recommends that coastal cities implement zoning regulations to separate aquaculture areas from port zones, thereby mitigating the devastating impact of PAHs and similar pollutants on the aquaculture industry.

Antioxidant and serum enzyme activities of the large yellow croaker (Larimichthys crocea) were analyzed to investigate the influences of genotype and water temperature. The activities of four antioxidant factors (peroxidase, catalase, total antioxidant capacity, and superoxide dismutase [SOD]) in the muscle and liver, as well as six serum enzymes (alkaline phosphatase, lipase, aspartate aminotransferase [AST], adenosine deaminase, γ-glutamyl transpeptidase (GGT), and alanine aminotransferase), were measured at natural water temperatures (20, 16, 12, 10, and 8 °C). Analysis of the antioxidant enzyme activities showed that genotype, temperature, and genotype × temperature interactions had different influences on the two tissues. In muscles, the impacts of these three effects on antioxidant enzyme activity were extremely significant, while in the liver, only the genetic effects were extremely significant and the temperature effect was insignificant. SOD exhibited the highest and the most stable activity and the best performance in terms of both activity and stability in both tissue types. Temperature, genotype, and genotype × temperature interactions all had a prominent impact on serum enzyme activity. The indicators that were the top performers in terms of activity, stability, and the optimal balance of both were AST, GGT, and AST, respectively. Our findings provide a theoretical basis for breeding with low-temperature tolerance based on antioxidant factors, reliable tolerance indicators, and the evaluation and early detection of low-temperature stress using serum-based enzyme biomarkers.

In response to the mounting pressures of climate change on aquaculture, this study investigates the potential of dietary fulvic acid (FA) supplementation to improve the resilience and growth performance of large yellow croaker (Larimichthys crocea) under conditions of high temperature stress. Conducted from July 14 to September 14, the experiment involved juvenile large yellow croakers acclimatized and then distributed into five treatment groups, with FA incorporated into their diets at concentrations of 0 g/kg, 2 g/kg, 4 g/kg, 8 g/kg, and 16 g/kg. Utilizing a multi-omics approach, we analyzed the impact of FA on the transcriptomic, metabolomic, and microbiomic profiles of the fish, focusing on the liver and gut tissues. The results demonstrated substantial improvements in weight gain and specific growth rates in the FA-supplemented groups, with the highest survival and growth metrics observed at the 0.8

The large yellow croaker (Larimichthys crocea) is a warm current migratory fish that experiences significant metabolic challenges during winter due to low temperatures and food shortages, leading to increased mortality rates. This study aimed to evaluate the effects of dihydromyricetin, a natural flavonoid, on the wintering performance of large yellow croakers. Over a 60-day period, fish fed dihydromyricetin showed improved growth rates and enhanced tolerance to low temperatures and water flow rates. A quadratic regression analysis of the relationship between specific growth rate (SGR) and dietary dihydromyricetin intake confirmed that at a feeding level of 205.4 mg/kg, the SGR reached a maximum of 1.07. Transcriptomic and metabolomic analyses indicated that dihydromyricetin activates the PPAR signaling pathway, which optimizes fatty acid metabolism and contributes to increased cold tolerance. Additionally, the supplementation improved the fish’s antibacterial and anti-inflammatory responses, essential for maintaining health under stress conditions. Notably, the addition of dihydromyricetin did not alter the diversity of the intestinal microbiota, suggesting that it enhances immunity without disrupting gut health. These findings provide valuable insights into the potential of dihydromyricetin as an effective dietary supplement to improve the overwintering survival and overall health of large yellow croakers in aquaculture settings. Implementing this strategy could significantly reduce winter mortality rates and promote sustainable practices in fish farming.

Bile acids (BAs) are known to confer health benefits across various fish species; nevertheless, the beneficial effects of ursodeoxycholic acid (UDCA) on immunity are largely unknown. This research investigated the impact of UDCA supplementation on nonspecific immunity, antioxidant capacity, and immune-related gene expression in juvenile large yellow croaker (Larimichthys crocea). The experimental diets were formulated with different UDCA supplement levels: 0 mg/kg (CON), 50 mg/kg (UL), 100 mg/kg (UM), and 500 mg/kg (UH). A total of four hundred fish were randomly distributed into 16 tanks with 25 fish per tank. Each diet was fed to four replicate groups twice daily. After a 70-day feeding trial, the results indicated that the UM diet significantly increased the percentage of nitroblue tetrazolium (NBT)-positive cells, serum lysozyme (LZM) activity, alternative complement pathway (ACP) activity, liver antioxidant capacity, and survival rate postcatch stress (P < 0.05). To elucidate the mechanisms underlying the immunomodulatory effects of UDCA, we conducted RNA sequencing of liver, intestinal, olfactory, and brain tissues from the CON and UM groups. Results indicated that UDCA upregulated genes associated with nonspecific immune responses, particularly those related to complement pathways (c3, c4a, and cfh), antioxidants (sod1, sod2, and gpx7), and lysozyme production (lyg). Conversely, the expression of chemokine genes (mrc1, ccl21, and ccr9) in the intestine significantly decreased (P < 0.05). Weighted gene coexpression network analysis (WGCNA) identified gene clusters linked to immunity primarily through the NF kappa B pathway (chuk, nfkb1, traf2, and ikbkb). In vitro experiments with primary hepatocytes demonstrated that incubation with 10 mu M UDCA markedly downregulated cytokine production genes (il1b and nfkb1) but upregulated antioxidant genes (gpx7, cat, sod1, and nrf2) following 1 mg/mL LPS challenge. In summary, the present study indicated that UDCA supplementation positively influences nonspecific immunity, enhances antioxidant responses, and reduces proinflammatory signaling in juvenile large yellow croaker.