Substrate is a critical environmental factor influencing growth and health of Penaeus japonicus. Traditional sandy substrates readily accumulate organic pollutants, deteriorating sediment conditions and increasing disease risks. In this 56-day trial, a shared-water indoor cage system was adopted to compare growth, physiological metabolism and hepatopancreatic transcriptomic responses between sandy-substrate (SL) and sand-free (SF) groups. On day 28, SF exhibited significantly higher survival (89.52 ± 1.56%, P < 0.05) than SL (77.14 ± 5.72%), while body length, body weight and yield per unit area remained comparable. SF showed elevated hepatopancreatic SOD, AKP, ACP, MDA and gill NKA activity, together with reduced intestinal amylase and protease activities (P < 0.05). At day 56, SF achieved higher cumulative survival (89.52 ± 3.30%) and yield (408.09 ± 24.19 g·m⁻²) than SL (76.19 ± 4.36%, 345.69 ± 27.58 g·m⁻²; P < 0.05). SF displayed markedly higher gill SOD, hepatopancreatic CAT, haemolymph LZM and PO activities, but lower hepatopancreatic MDA, AKP, ACP, gill NKA and intestinal digestive enzyme activities (P < 0.01), reflecting long-term physiological adaptation. Transcriptomics revealed a “short-term suppression, long-term activation” pattern of differentially expressed genes; core PPI hub proteins shifted from Hspbp1/Hif1a to Bub1b/plk1. Collectively, sand-free culture improves P. japonicus survival, and shrimp adapt to sand-free surroundings via sequential modulation of antioxidant, immune and metabolic pathways.
Global climate change has led to rising marine temperatures, making high temperature (HT) a major threat to bivalve aquaculture. This study investigated the effects of HT on intestinal damage, microbiota, immune responses, and molecular mechanisms in the razor clam (Sinonovacula constricta), aiming to provide a theoretical basis for understanding bivalve adaptation to heat stress and informing aquaculture management. The results showed that HT significantly inhibited the filter-feeding activity of clams. Within one week of continuous HT, the mortality rate of clams reached 42%. HT caused severe damage to the mucosal ridges. HT significantly increased malondialdehyde content, suppressed superoxide dismutase activity, and reduced the activities of intestinal immune-related enzymes (lysozyme, acid phosphatase, and alkaline phosphatase). Additionally, HT reshaped the intestinal microbial composition and reduced microbial abundance. Intestinal transcriptome analysis revealed that HT significantly inhibited the intestinal oxidative phosphorylation process, leading to mitochondrial dysfunction, while the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) innate immune pathway and inflammation-related genes were significantly upregulated. Further verification experiments showed that HT significantly reduced the intestinal adenosine triphosphate content and increased the content of cyclic guanosine monophosphate-adenosine monophosphate. HT caused obvious morphological damage to intestinal mitochondria. These results confirmed the activation of the STING signaling pathway and its downstream inflammatory response. This study systematically reveals the impact mechanism of HT on the intestinal physiology and molecular regulation of razor clam, enriches the theoretical research on the environmental stress response of bivalves, and provides theoretical support for the prevention and control of HT, optimization of aquaculture environments, and breeding of stress-resistant varieties during razor clam aquaculture.
Protein is a critical nutrient during fish reproduction, and its intake level directly affects gonadal development and reproductive performance of broodstock. This study evaluated the effects of three dietary crude protein levels-31.21% (Group A), 38.52% (Group B), and 45.80% (Group C)-on ovarian development in broodstock of spotted scat (Scatophagus argus). After 8 weeks of feeding, fish in Group B exhibited the highest gonadosomatic index (GSI: 7.74 ± 1.37%), serum estradiol (E2: 229.64 ± 31.88 pg/mL), and vitellogenin (VTG: 1056.66 ± 180.11 μg/mL) levels, which were significantly higher than those in the 31.21% protein group (P < 0.05) but did not differ significantly from those in the 45.80% group. Hepatic total amino acid and essential amino acid contents increased with rising dietary protein levels. Liver transcriptome analysis (Group A vs. Group B) identified 416 differentially expressed genes. qRT-PCR validation confirmed that genes related to sex steroid hormones, ovarian development, and glucose-lipid metabolism such as dgat1, acot1, cyp7a1, and kifc3 were significantly upregulated, whereas rgs3, fstl3, prg4, and socs2 were significantly downregulated. These results indicate that a dietary protein level of 38.52% is beneficial for ovarian development in Scatophagus argus broodstock. Protein nutrition may regulate ovarian development by optimizing glucose-lipid metabolism and feedback regulating the related processes of the hypothalamic-pituitary-gonadal (HPG) axis through liver metabolic pathways.
The monsoonal climate with varying hydrodynamic conditions, prevalence of traditional cultural practices, and difficulties in suitable area identification are the main obstacles to the growth of seaweed farming activities in Bangladesh. The present study introduces an innovative floating net cage system to improve seaweed mariculture techniques, specifically for cultivating Gracilaria. This system was tested in the Moheshkhali Channel waters of Bangladesh to alter the hydrodynamic forces within the cage, thereby enhancing seaweed growth. The production system successfully reduced ~28% sea surface current velocity inside the cage and yielded 1.77–3.50 kg m−2 per month at 10.37–14.65% daily growth rate during the period of November to April. Moreover, this study attempted to develop a seaweed site suitability index (SSI) model using suitability functions for different environmental variables in order to predict suitable seasons and potential areas for seaweed aquaculture development in Moheshkhali Channel. A large array of environmental datasets was created to feed the SSI model, with monthly sampling conducted across 56 geospatial locations within the ~52 km² area of the Moheshkhali Channel. The monsoon showed the highest environmental variability, differing from other seasons. Winter and post-monsoon were identified as the most suitable seasons, when 32–39 km2 area of the channel was predicted as suitable (SSI score > 0.70) for seaweed aquaculture development. The findings of the study on the new production system and suitable area identification can aid in the horizontal expansion of seaweed culture and contribute to enhance seaweed production in Bangladesh.
In response to current restrictions on antibiotic use in aquaculture, developing eco-friendly feed additives as alternatives is essential to sustain industry growth. This study evaluated the effects of dietary sodium fulvate (SF) on growth, intestinal health, antioxidant capacity, and immune responses in largemouth bass (Micropterus salmoides). Six experimental diets containing 0%, 0.05%, 0.1%, 0.2%, 0.4%, and 0.8% SF were formulated and fed to fish maintained in three replicate cages over 9 weeks. Dietary SF inclusion did not significantly affect growth performance (weight gain rate, specific growth rate) or feed utilization (feed conversion rate, protein efficiency ratio) (P > 0.05). However, second-order polynomial regression indicated that dietary inclusion of 0.17% SF maximized intestinal trypsin activity (P < 0.05), whereas supplementation with 0.30%–0.58% SF reduced plasma diamine oxidase, endothelin-1, and lipopolysaccharide concentrations. Furthermore, supplementation with 0.44%–0.56% SF significantly enhanced the Shannon diversity index and increased the relative abundance of Fusobacteria, Ralstonia, and Cetobacterium. Dietary inclusion of 0.06%–0.46% SF enhanced intestinal superoxide dismutase and catalase activities; increased serum complement 3, complement 4, immunoglobulin M levels, and the relative expression levels of TNF-α, IL-10, and TGF-β1; and reduced intestinal malondialdehyde level. Collectively, these findings indicate that dietary supplementation with 0.06%–0.58% SF promoted fish health by improving intestinal digestive capacity, reinforcing mucosal barrier integrity, and enhancing antioxidant and immune responses, underscoring its potential as a functional feed additive for antibiotic-free aquaculture.
Ammonia is a pervasive environmental stressor in intensive aquaculture systems that compromises fish health and productivity. Here, we characterized histological, physiological, and transcriptomic responses in the gill, kidney, and liver of surviving Epinephelus coioides following initiation of acute ammonia exposure (31–32 mg/L TAN; estimated 1.13–1.80 mg/L NH3-N) for up to 72 h. Ammonia exposure induced pronounced organ-specific dysfunction and temporally dynamic responses. Histologically, the gill progressed from lamellar thickening and chloride cell hypertrophy (12 h) to severe lamellar fusion and edema (72 h). In the kidney, glomerular atrophy was persistent, whereas renal tubular lumen diameter increased at 12 h and returned to near-baseline values by 72 h. The liver showed progressive vascular congestion and hepatocellular distortion. Physiologically, branchial NKA was suppressed throughout the exposure, while SOD activity decreased significantly at 12 h. Conversely, the kidney exhibited consistently elevated SOD and CAT at both time points, accompanied by a transient spike in NKA at 12 h and a delayed upregulation of GST at 72 h. Hepatic SOD and CAT activities increased at 12 h; by 72 h, SOD decreased below the baseline level, whereas CAT returned approximately to baseline. Transcriptomic analyses identified tissue-associated co-expression modules and mmp13 as a commonly dysregulated candidate gene. Overall, surviving fish showed concurrent but organ-specific responses to acute ammonia exposure.
Bacterial protein meals (BPMs) hold strong potential as sustainable alternative protein sources for aquafeeds, yet their ingredient apparent digestibility coefficients (IADCs) remain poorly characterized, limiting broader adoption. This study evaluated the digestibility of a bacterial protein meal (BPM) derived from brewery by-products using a diet-substitution method, together with the associated digestive enzymatic responses, in barramundi (Lates calcarifer) and Mozambique tilapia (Oreochromis mossambicus). Two cohorts of 150 fish per species (48.9 ± 4.2 g barramundi; 48.7 ± 11.4 g tilapia) were reared in recirculating brackish-water systems (28 °C; 5 ppt) across two independent trials. IADCs were determined for 42 fatty acids and 17 amino acids, along with Michaelis–Menten parameters (Km, Vmax) for trypsin, chymotrypsin, and leucine aminopeptidase extracted from fish gut. Protein and energy IADCs of BPM were 71.8 ± 5.3% and 64.0 ± 4.3% in tilapia, and 88.1 ± 0.9% and 75.1 ± 4.5% in barramundi. In tilapia, essential amino acid digestibility exceeded 85% except for alanine, histidine, threonine, and valine. BPM inclusion had negligible effects on lipid and fatty-acid digestibility. With control diet, Km values for trypsin, chymotrypsin, and leucine aminopeptidase were 0.01, 0.24, and 0.13 mM in tilapia, and 0.02, 0.43, and 0.07 mM in barramundi respectively. In both species, concurrent shifts in Vmax and Km were observed between dietary treatments, indicating a degree of digestive proteome plasticity that allows compensatory regulation of enzyme activity—an effect more pronounced in barramundi than in Mozambique tilapia. Overall, the tested BPM was highly digestible in both species and had minimal impact on gut enzyme functionality, supporting its suitability for inclusion in commercial aquafeed formulations.
Variations in temperature and salinity are among the most important climate stressors affecting estuarine ecosystems. Shellfish beds are unique, highly productive habitats that are particularly vulnerable to these stressors. The changing conditions can impair bivalve physiological performance and alter community structure, with substantial ecological and socio-economic impacts for coastal communities. Changes that affect juvenile stages are of particular concern, as they may compromise population dynamics and long-term persistence. We evaluated the sublethal effects of short-term seawater warming and hyposalinity events, each acting independently, under typical conditions in the study area. In two laboratory experiments, juveniles of four commercially important bivalve species—Ruditapes decussatus, Ruditapes philippinarum, Venerupis corrugata, and Cerastoderma edule—were exposed to a range of temperature and salinity levels, while key components of the scope for growth, including clearance, respiration and excretion rates, were measured. Temperature responses were species- and size-dependent, whereas hyposalinity thresholds closely matched those reported for adults, suggesting that species-specific tolerance limits are conserved across life stages. Notably, the effects of reduced salinity were stronger than those of elevated temperature. The findings emphasize the heightened vulnerability of V. corrugata juveniles to warming and reduced salinity, indicating that climate-driven fluctuations in temperature and salinity could disproportionately affect certain bivalve species under global change.
This research aimed to examine how graded dietary DHA/EPA ratios influence growth performance, lipid metabolism, and antioxidant capacity in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂). Five experimental diets, formulated to have 48% protein and 12% lipid, were designed with DHA/EPA ratios of 0.77, 1.31, 2.44, 3.20, and 4.10. A total of 450 fish (9.87 ± 0.02 g, 40 days of age) were arbitrarily allocated into 5 groups with 3 replicates each for a 56 d experimental period. Analysis results showed that:(1) As dietary DHA/EPA ratios rose, weight gain rate (WG) and specific growth rate (SGR) exhibited a pattern of first increasing and then decreasing. WG and SGR attained its peak value in the 1.31 group, which were notably higher when compared with the control (0.77) and the highest ratio (4.10) groups (P < 0.05). (2) The relative proportion of DHA in muscle was significantly higher than that in liver. With increasing dietary DHA/EPA ratios, the DHA/EPA ratios in both muscle and liver also increased significantly (P < 0.05).(3) A higher DHA/EPA ratio significantly decreased the serum contents of triglycerides (TG) and glucose (GLU) (P < 0.05). Meanwhile, it markedly increased the serum content of high-density lipoprotein cholesterol (HDL-C) (P < 0.05). (4) When the dietary DHA/EPA ratios were 2.44 and 3.20, the activities of superoxide dismutase (SOD), catalase (CAT) and antioxidant capacity (T-AOC) in serum and liver were the highest (P < 0.05), and the level of malondialdehyde (MDA) was the lowest (P < 0.05). Furthermore, When the DHA/EPA ratio was 2.44, the activity and gene expression of hepatic carnitine palmitoyltransferase-1 (CPT-1) were significantly upregulated, while the activity of fatty acid synthase (FAS) was inhibited (P < 0.05).In summary, dietary DHA/EPA ratios ranging from 1.31 to 3.20 optimized growth performance, enhanced antioxidant capacity, and modulated lipid metabolism in hybrid grouper. However, an excessively high ratio (4.10) may induce oxidative stress and inhibit growth. The WG was fitted using a quadratic regression model, and it was determined that the theoretical optimal ratio of DHA/EPA for achieving the best growth performance in hybrid grouper was 2.125, which falls within the above appropriate range.
Although insect-derived ingredients have been extensively investigated as high-inclusion protein sources in aquafeeds, little is known about the molecular mechanisms and immunomodulatory effects of low-level dietary supplementation. We previously reported that dietary supplementation with defatted silkworm pupae (DSP) enhances innate immune responses. However, whether DSP supplementation modulates humoral and inflammatory immune responses following vaccination remains unclear. In this study, we investigated the effects of DSP supplementation on the immune response in yellowtail following immunization with Vibrio anguillarum serotype JO-3 formalin-killed cells (FKC) through complementary in vivo and ex vivo experiment. Serum IgM levels, Serum antibody titer and immune-related gene expression were evaluated after vaccination under DSP feeding. At two weeks post-vaccination, fish fed 0.01% and 0.1% DSP showed significantly higher serum IgM levels and a tendency toward higher antibody titers compared with the control group. In addition, the expression of immunoglobulin light chain and mhc2β was upregulated at this time point, providing further evidence that antibody production was enhanced at the transcriptional level. To assess short-term immune responses, splenic leukocytes were isolated from DSP-fed fish and stimulated with V. anguillarum FKC. The 0.1% DSP group exhibited suppressed tnf-α expression and modulated il-10 expression, suggesting the balancing of inflammatory responses. Conversely, il-1β expression was induced more rapidly and strongly, indicating activation of the early immune response. These findings demonstrate that low-level dietary DSP supplementation coordinately modulates humoral and inflammatory immune responses following immunization, providing mechanistic insight into the immunomodulatory actions of low-level DSP supplementation.
Cantharides is a general term for cantharidin-rich beetles and an insect-derived medicine as listed in the Chinese Pharmacopoeia. Cantharides larvae feed exclusively on locust eggs in nature, posing significant challenges for their artificial rearing. The current artificial feed is effective for rearing older instars but exhibits lower fitness for earlier ones. This study analyzed the nutritional content of natural food (locust eggs) and a basic artificial feed (BAF), revealing that the BAF had higher total sugar content but lacked sufficient protein and fat. Based on these findings, we developed an improved artificial feed (IAF) with enhanced protein and lipid content. The larvae fed the IAF exhibited higher survival rates and food conversion efficiency than those fed the BAF; however, these metrics remained inferior to those in larvae fed locust eggs. Mass spectrometry analysis revealed that 1425 proteins and 683 lipids were significantly more abundant in the IAF than in locust eggs, whereas 21 proteins and 378 lipids were less abundant. Proteins and lipids with higher amounts in IAF than in locust eggs positively correlated with larval food utilization and growth, but were inversely associated with survival rates. Conversely, compounds absent from IAF exhibited an opposite trend. This study identified critical nutritional disparities between the IAF and locust eggs, indicating potential impact on the growth and development of cantharides larvae. These findings provide scientific insights into the feeding plasticity of cantharides larvae and suggest potential strategies for optimizing artificial feed formulation for cantharides larvae.
Starvation is a natural stressor for fish, during which the liver adapts lipid metabolism to supply energy. Although our previous research clarified the effects of starvation on body composition in tiger puffer, the impact on hepatic lipid metabolism and the underlying molecular mechanism remains unknown. Here, 900 juvenile tiger puffer (19.50 ± 0.05 g) were randomly divided into 18 tanks (six tanks per group), and fed diets containing 8%, 12%, or 16% lipid for nine weeks, followed by a 31-day starvation period. Samples were collected at the end of the feeding trial and at Day 0, 1, 4, 9, 16, and 31 of the starvation periods. The results revealed that starvation remodeled hepatic lipid metabolism. Specifically, with prolonged starvation, lipogenesis was initially inhibited and then activated, whereas lipolysis, fatty acid β‑oxidation and lipid transport were promoted, indicating a suppression of lipid anabolism and an enhancement of mobilization to meet energy demands. Among the lipid metabolism-related transcription factors, hnf4α expression was significantly influenced by the interaction between starvation and dietary lipid level, and increased over the starvation period. Subsequent in vivo and in vitro experiments using the Hnf4α agonist benfluorex hydrochloride or inhibitor BI6015 confirmed that Hnf4α activation lowered hepatic lipid contents and enhanced fatty acid β‑oxidation, whereas its inhibition produced the opposite effects. These findings indicate that Hnf4α regulates hepatic lipid mobilization in tiger puffer, offering insights into lipid metabolic adaptation during starvation and identifying Hnf4α as a potential target for improving lipid utilization.
To investigated the effects of temperature stress, on the brine shrimp Artemia franciscana, we examined the life parameters (growth [body size] and hatching rate), reactive oxygen species (ROS), antioxidant enzymatic activities (e.g., glutathione S-transferase [GST], catalase [CAT], and superoxide dismutase [SOD]) with transcriptional regulation of heat shock protein (hsp) genes in response to temperature changes. Significant changes in body size and hatching success were observed in response to temperature changes. changes in reactive oxygen species (ROS) levels and antioxidant enzyme activities were induced, indicating ROS-mediated activation of defense system, resulting in harmful effects on growth and hatching successes of A. franciscana. Additionally, transcriptional regulation of the four hsp genes (hsp26, hsp40, hsp70, and hsp90) was significantly modulated in response to temperature changes. In particular, hsp40, hsp70, and hsp90 were significantly increased in response to temperature changes, suggesting that hsp genes are crucial role in cellular defense mechanisms and hsp40, hsp70, and hsp90 could be useful as molecular biomarkers for temperature stress. Taken together, we suggested that temperature changes can induce oxidative stress, leading to modulation of antioxidant and stress defense mechanisms in the brine shrimp A. franciscana. Overall, the results of this study will provide a better understanding of the effects of temperature changes on body size and biomolecular response of the antioxidant defense system and hsps in brine shrimp Artemia.
Red-spotted grouper nervous necrosis virus (RGNNV) exhibits high pathogenicity in larval Cephalopholis sonnerati, resulting in significant losses in fish aquaculture. However, the immune interaction mechanism of C. sonnerati to RGNNV infection remains unclear. This study conducted pathological and transcriptome analysis using healthy and natural infection models. Severe pathological changes were observed in infected individuals, including neuronal vacuolization and apoptosis. Transcriptome analysis revealed a preponderance of up-regulated genes upon RGNNV infection. The transcript levels of genes involved in immune-related pathways (JAK-STAT signaling pathway, cytokine-cytokine receptor interaction, NF-kappa B signaling pathway and necroptosis), including IL15, IL1R1, CXCR3, CXCL9 RIPK3, MLKL were up-regulated in the infected brain. The transcriptome analysis of artificial infected brain cells(TGB) further validate the consistent functional enrichment. Additionally, antiviral genes were consistently up-regulated in the infected brain tissue and brain cells, such as SAMD9L, TRIM25, IRF1, STAT1, TLR3, SOCS1. Collectively, these findings indicate that excessive inflammatory activation, exacerbated necroptosis and a limited antiviral response may potentially involved in the brain tissue and cells during RGNNV infection. The findings offer valuable reference data to better understand pathogenic effects and host-virus interactions in C. sonnerati, supporting the development of effective control strategies against RGNNV infection.
Feeding attractants are widely used in aquaculture to enhance feed intake and support growth, but their evaluation requires robust and standardised testing protocols. Prior familiarisation involves repeated exposure to the testing tank to reduce novelty-induced stress and redirect animal attention toward tested feed. This study examined whether prior familiarisation influences stress responses and feeding behaviour of juvenile Pacific white shrimp Penaeus vannamei (7.88 ± 0.98 cm), and assessed its relevance for evaluating the attractiveness and palatability of a mix of free amino acids (MFAA). In Experiment 1, we assessed familiarisation under moderately challenging conditions, using shrimp’s usual daily feed. Shrimp were either familiarised (1 h/day for three days) or not to the testing tank, and tested with or without feed. Familiarisation had no effect on stress or feeding behaviour, whereas feed presence increased tail flips and reduced thigmotaxis. In Experiment 2, we assessed familiarisation under more challenging conditions – representative of typical feed evaluation assays – where shrimp are repeatedly exposed to novel feeds. Familiarised and non-familiarised shrimp were successively exposed to four feed treatments (No Feed, uncoated Blank Diet, Blank Diet coated with 0.5 or 1% of MFAA). Familiarisation increased feed consumption but did not improve shrimp’s ability to discriminate feeds, calling into question the relevance of this time- and resource-intensive procedure in feeding tests. Shrimp consumed more MFAA-coated feed regardless of familiarisation, confirming its palatability. Overall, these results suggest that the effects of familiarisation depend on the testing context and may be more beneficial when shrimp encounter novel feeds. Given the economic importance of P. vannamei, refining testing procedures is essential to strengthen the assessment of feed additives in aquaculture.
Monitoring fish growth is critical for intensive aquaculture, yet traditional manual weighing methods are labor-intensive and inefficient. This study proposes FishPose-tracking, an enhanced deep learning model that automates keypoint detection and tracking of fish, improving the efficiency and accuracy of growth monitoring in complex aquaculture environments. Built upon the YOLOv8-Pose model, FishPose-tracking integrates several advanced components: underwater image enhancement, precise keypoint detection, posture estimation, and continuous fish tracking. Image quality is optimized through multi-level bilateral filtering and regional dark channel dehazing, addressing challenges posed by turbid and low-light underwater conditions. To improve feature extraction, FishPose-tracking incorporates the Swin Transformer encoder, which offers robust multi-scale capabilities, and the STIAU module, which enhances temporal consistency across video frames to reduce detection errors from motion blur and occlusion. The model was trained on a diverse dataset of 10,000 images encompassing multiple fish species under varying degrees of occlusion. Experimental evaluations show that FishPose-tracking improves detection and tracking precision, achieving mean Average Precision scores of 99.37% (mAP50) and 87.39% (mAP50:95), representing improvements of 13.74% and 8.86%, respectively, over baseline models. Residual analysis confirmed the high accuracy of the model, with the median keypoint error for the five species being less than or equal to ±2 pixels (IQR ≤ 3 pixels). FishPose-tracking provides a robust and real-time capable monitoring solution adaptable to various aquaculture environments. Future work will explore further enhancements, including integration with multi-source data and large-scale deployments.
Skin pigmentation is a critical determinant of quality and market value in farmed fish, while environmental stressors such as hypoxia can induce oxidative stress and metabolic disorders, thereby threatening fish health and aquaculture sustainability. The present study investigated the effects of dietary lutein and zeaxanthin on skin pigmentation, hepatic lipid metabolism, and oxidative stress responses in yellow catfish (Pelteobagrus fulvidraco) through a 50-day feeding trial followed by an acute hypoxia challenge. Fish (initial body weight: 25.98 ± 0.03 g) were randomly assigned to three experimental diets: a basal control diet (Con), or the basal diet supplemented with 0.2% lutein (Lut) or 0.2% zeaxanthin (Zea). Although no significant differences in growth performance were observed among dietary groups, skin yellowness and total carotenoid deposition in both skin and liver were significantly elevated in the Lut group (P < 0.05), followed by the Zea group. Lipidomic profiling revealed that both lutein and zeaxanthin supplementation modulated multiple lipid classes, including glycerophospholipids (GP), glycerolipids (GL), sphingolipids (SP), sterols (ST), and fatty acids (FA) in liver and skin tissues (P < 0.05). Skin lutein content exhibited strong positive correlations with phosphatidylcholine (PC) levels (R=0.978, P < 0.01) and the expression of lipid transport-related genes cd36 (R=0.978) and scarb1 (R=0.977, P < 0.01). Under acute hypoxic stress, fish fed Lut or Zea diets displayed significantly higher plasma SOD activity and lower levels of glucose, lactic acid, and MDA compared to the control group (P < 0.05). Moreover, lutein supplementation specifically upregulated the expression of antioxidant and anti-apoptotic genes (nrf2, sod, gpx, bcl2) while downregulating pro-apoptotic genes (p53, casp3) in the liver (P < 0.05). In conclusion, dietary lutein plays a more prominent role than zeaxanthin in enhancing skin pigmentation and antioxidant defense in yellow catfish, and its functional efficacy is closely associated with lipid metabolism and carotenoid transport mechanisms.
Intensive aquaculture at high densities readily elevates ammonia concentrations in the water to toxic levels, triggering a series of ecotoxicological effects. To explore the toxic effects of continuous exposure to environmentally relevant concentrations of ammonia on juvenile Micropterus salmoides, this work investigated the changes in gill histological structure, physiological enzyme activities, and metabolomics after 21 days of exposure to various ammonia concentrations (0, 4, 8, and 16 mg/L). The results demonstrated that ammonia exposure induced gill damage, leading to significant inhibition of the SOD, GPX activities, and GSH content while elevating the MDA levels and causing oxidative damage. Furthermore, the levels of Attacin, LYS, IgA, and TCR were significantly increased, suggesting that Micropterus salmoides could avoid pathogenic diseases by enhancing innate immune factors and adaptive immune molecules. The Na+/K+-ATPase activity exhibited an initial increase followed by a decrease, inhibiting ammonia transport. The reduction of Ca2+/Mg2+-ATPase may result in excessive intracellular accumulation of Ca2+, leading to cellular homeostasis disruption. The IBR analysis indicated that the Ca2+-Mg2+-ATPase, MDA, TCR can serve as biomarkers of ammonia exposure. Additionally, Micropterus salmoides may activate the ornithine-urea cycle to reduce ammonia accumulation and eliminate its toxicity under ammonia stress. In conclusion, from the perspective of gill toxicity effects induced by ammonia exposure alone, ammonia concentrations should be controlled within 4 mg/L and adjusted within 3 days. The results of this study have important guiding significance for the healthy cultivation of Micropterus salmoides.
Agonistic behaviour during early developmental stages poses a significant challenge in marine fishes. In Acanthopagrus berda, observations revealed size-specific mortality clustered between 1.5 and 2.5 cm standard length (SL), prompting behavioural investigations. Controlled experiments were conducted to evaluate the effects of crowding (100, 200, and 300 fish / m³) and size variation (segregated and unsegregated groups) on growth, survival, and aggression in 100 L seawater aquaria. While crowding had no significant effect (p > 0.05) on final length or growth, size segregation significantly (p < 0.05) affected survival and growth. Despite having greater size variations; unsegregated (mixed) groups exhibited higher survival and growth than segregated (uniform) groups with higher mortality. Morphological analysis revealed that juveniles above 2.5 cm SL possess prominent canine-like teeth, enabling targeted attacks on smaller conspecifics. Across all trials, mortalities were consistently recorded in individuals < 2.5 cm SL, indicating a critical size threshold for vulnerability. These results highlight a behavioural size dominance hierarchy in A. berda juveniles, likely mediated by ontogenetic dentition development, and underscore the importance of periodic culling off of individuals above 2.5 cm from the nursery tanks to mitigate aggression-induced mortality. This study offers novel insights into intra-specific aggression patterns during early development and provides practical guidelines for behavioural management in hatchery systems.
Acanthocephalan infections are a major constraint on swamp eel (Monopterus albus) production, yet how hosts coordinate systemic responses beyond the intestinal infection site remains poorly understood. Here, we profiled multi-organ transcriptomic responses associated with natural infection by the intestinal acanthocephalan Pallisentis (Neosentis) celatus. RNA-seq was performed on the intestine, liver, kidney, and spleen from infected and acanthocephalan-negative eels, followed by differential-expression, functional-enrichment, and multi-level co-expression network analyses. Infection status was associated with strongly tissue-dependent transcriptional programs and limited overlap of differentially expressed genes across organs. Intestinal and hepatic responses involved bile-acid, xenobiotic, and other metabolic pathways, whereas kidney responses involved cytoskeletal, junctional, and membrane-signaling pathways. The spleen showed the most prominent immune-related transcriptional remodeling. Network analysis identified a spleen-derived infection-associated module enriched for endocytosis/phagosome and cellular quality-control processes, although individual module genes showed mixed directions and most did not meet the single-gene differential-expression threshold. Gene set variation analysis further showed higher macrophage-associated and lower T-cell-associated signatures in infected spleens. Together, the results define organ-stratified transcriptional associations with natural P. (N.) celatus infection and prioritize candidate pathways and modules for future functional validation.
