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Simple Summary: Aeromonas hydrophila and Aeromonas veronii are common pathogenic bacteria in grass carp aquaculture. Through comprehensive histopathological analysis and molecular characterization, we found that both pathogens caused severe cellular necrosis, cytoplasmic vacuolization, and hemorrhage in the liver of grass carp, similar to the manifestations of infection in other aquatic animals. The grass carp showed complex regulation of immune and metabolic responses during infection, especially activation of Toll-like receptors and TNF signaling pathways. Our findings provide new insights into host–pathogen interactions during Aeromonas co-infection in grass carp and provide a scientific basis for the development of prevention and control strategies. The grass carp (Ctenopharyngodon idella) is highly susceptible to infections caused by Aeromonas species, particularly A. hydrophila and A. veronii. However, the immunological mechanisms underlying co-infection by these pathogens remain largely uncharted. This study investigated the pathogenesis and host immune response in grass carp following concurrent infection with A. hydrophila and A. veronii. Mortality was observed as early as 24 h post-infection, with cumulative mortality reaching 68%. Quantitative analysis demonstrated significantly elevated bacterial loads in hepatic tissue at 3 days post-infection (dpi). Histopathological evaluation revealed severe hepatic lesions characterized by cellular necrosis, cytoplasmic vacuolization, and hemorrhagic manifestations. Comparative transcriptomic analysis of hepatic tissues between co-infected and control specimens identified 868 and 411 differentially expressed genes (DEGs) at 1 and 5 dpi, respectively. Gene ontology and KEGG pathway analyses revealed significant enrichment of immune-related genes primarily associated with Toll-like receptor signaling and TNF signaling cascades. Notably, metabolic pathways showed substantial suppression while immune responses were significantly activated after infected. These findings provide novel insights into the host–pathogen interactions during Aeromonas co-infection in grass carp, which may facilitate the development of effective prevention and control strategies. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila is an important etiologic agent, triggering an increased trend of disease outbreak in fish farming. In this investigation, we evaluated pathological response in the midgut and liver of three types of grass carps after gut infection. Severe pathological levels of tissue necrosis were observed in common grass carp (GC) and gynogenetic grass carp (GGC), but mild pathological symptom was detected in hybrid grass carp (DRGC), along with the dramatically increased number of goblet cells. Moreover, three types of grass carps showed upregulated levels of immune gene patterns and antioxidant abilities, whereas inflammatory cytokine expression levels in hybrid grass carp (DRGC) were lower than that of gynogenetic grass carp (GGC) and common grass carp (GC). These results suggested that DRGC may exhibit a disease tolerance against A. hydrophila-induced tissue inflammation. [ABSTRACT FROM AUTHOR]

Exosomes regulate lipid metabolism by carrying miRNAs, nucleic acids, and proteins, thereby influencing the function of receptor cells. Glucose-regulated protein 78 (GRP78) is also involved in the regulation of lipid metabolism. However, it remains unclear whether exosomes derived from fatty hepatocytes (OA-Exo) regulate lipid metabolism through the enrichment of GRP78. In this study, we observed the expression of GRP78 was significantly increased in fatty hepatocytes (incubating hepatocytes with oleic acid (OA) for 24 h) and OA-Exo (P < 0.05). In addition, OA-Exo (50 μg/mL) and GRP78 protein (1 μg/mL) significant increased the content of triacylglycerol (TG) and total cholesterol (TC), as well as up-regulated the expression of GRP78 and inositol-requiring enzyme-1alpha (IRE1α) protein (P < 0.05). We further used YUM70 (an inhibitor of GRP78) to inhibit endogenous GRP78, and compared with the YUM70 group, OA-Exo reversed the effect of YUM70 and increased the content of TG, TC, and the expression of GRP78 protein in hepatocytes (P < 0.05). Furthermore, the inhibition of the IRE1α pathway with 4μ8C resulted in a significant decrease in TG content compared to the control group (P < 0.05). However, when compared with the 4μ8C group, OA-Exo and GRP78 reversed the effect of 4μ8C and significantly increased TG content (P < 0.05). Taken together, these results indicated that OA-Exo activated IRE1α to promote lipid accumulation in hepatocytes through the enrichment of GRP78. This study provided a new perspective for further exploration of exosomal lipid metabolism in fish. [ABSTRACT FROM AUTHOR]

The pomegranate plant is considered one of the medicinal herbs rich in antioxidants that can be used in aquaculture to support immunity and health. The objective of this investigation was to ascertain the impact of pomegranate peel (Punica granatum) extract (PPE) on growth performance, the intestinal bacteria count, total number of fungi and histological analysis of the grass carp. One hundred five fingerlings (11.04±0.22g) were distributed among 21 aquariums (60-L) in a completely randomized design (triplicated) and fed diets containing 0, 0.5, and 1% PPE for 70 days at a feeding rate of 3% body weight. A spectrophotometry assessment indicated for PPE that the total phenol content was 151.09 and 175.95 GAE/100 g, and flavonoid content was 36.04 and 42.89 RE/100 g, respectively. The results of the present work revealed that growth indicators (final weight, weight gain, specific growth rate (SGR), and feed conversion ratio (FCR)) increased (P<0.05) in the PPE group in comparison to the control group. PPE had an impact on the total count of aerobic bacteria or lactic acid bacteria (LAB), but the experimental treatments dramatically decreased the amount of enteric Gram-negative bacteria (P<0.05). The total fungi count showed a significant increase in all treated fish (P<0.05). Also, histological examination showed improvement and elongation of the villi, as well as an increase in goblet cells for the treatments supplemented with PPE. Therefore, it is recommended to use PPE (0.5%) as a diet additive for grass carp to improve their growth performance and health. [ABSTRACT FROM AUTHOR]

The biofloc technology (BFT) offers benefits in improving feed utilization and reducing the feed conversion ratio compared to the recirculating aquaculture system (RAS). In this study, high-throughput 16S rRNA gene sequencing was employed to investigate and compare the bacterial communities in these aquaculture systems and the gut microbiota of grass carp reared in them. We observed a significant distinction between the microbial communities of the aquaculture systems and the intestinal microbiota of grass carp. The genera cetobacterium and bacillus were more abundant in the BFT system, accounting for only 0.05% and 0.25% in the RAS. Our study also demonstrated that BFT could influence the intestinal microorganisms of grass carp (Ctenopharyngodon Idella) by reducing the relative abundance of burkholderia-caballeronia-paraburkholderia and increasing that of cetobacterium. Based on bugBase community predictions, the potential pathogenicity in BFT and grass carp intestine was lower than in RAS. Regarding gene expression in the grass carp intestine, immunosuppressive genes showed higher expression, while pro-inflammatory genes exhibited lower expression in grass carp reared in BFT. Furthermore, the final average length and weight of grass carp in the BFT system were significantly higher than those in the RAS. This study provides valuable insights into gut microbiome ecology in relation to two grass carp aquaculture systems, which could be effectively applied in grass carp management to promote health and improve water quality. [ABSTRACT FROM AUTHOR]

Grass carp belongs to Cypriniformes, Cyprinidae, and Cyprinus family, and is typically referred to as the four famous domestic fishes, black carp, silver carp, and bighead carp, respectively. The annual production of Chinese grass carp is consistently among the highest, with an output of 5.905 million tons in 2022, accounting for 24.3% of total of freshwater fish production. Reproduction is the core process of fish reproduction. Normal gonad development is a prerequisite for fish reproduction. At present, there are few reports on the sex differentiation of Chinese grass carp. Studying the differentiation and development of grass carp gonads can provide a typical model for gonadal development of cyprinid fish. In contrast, the start and completion time of gonadal differentiation are one of the key factors inducing sex reversal in fish using hormones. Research on gonadal differentiation and development in grass carp can also lay the foundation for the establishment of a unisexual population of grass carp.Sex-related genes play important roles in biological processes such as sex determination, gonadal differentiation, and reproduction and development in fish. In most differentiated teleost fish, genes such as dmrt1, sox9, foxl2, amh, and cyp19a1a, are considered the key genes involved in sex regulation. cyp19a1a plays a key role in the gonadal differentiation and ovarian development of teleost fish by aromatizing androgens into estrogen via aromatase activity. This gene is specifically expressed in the gonads and is used served as a characteristic gene for sex differentiation towards females. Anti-Müllerian hormone (amh) regulates the structure of reproductive organs and the differentiation and development of reproductive cells. In fish such as carp, rainbow trout, and grass carp, the expression level of the amh gene in the testes is significantly higher than that in the ovaries, and is often used as a characteristic gene for male differentiation.To explore the sex differentiation and developmental patterns of grass carp gonads, this study analyzed the tissue structure and expression differences of sex characteristic genes cyp19a1a and amh in the gonads of grass carp at 1, 2, 3, 4, 5, 6, 12, 24, 36, and 48 months of age using tissue sectioning technology and real-time fluorescence quantification technology. The results of tissue sectioning showed that grass carp exhibited reproductive ridges at 1-month-old. At 2 months of age, primitive germ cells were first observed in the reproductive crest, marking the formation of their primitive gonads. At 3-month- old, ovarian cavities and lobules were observed in the gonads of female grass carp. At 4-month-old, oogonia was observed, indicating anatomical differentiation at 3-month-old and cytological differentiation at 4-month-old. At the age of 4 and 5 months, ductus deferens and spermatogonia were respectively observed in male grass carp gonads, indicating anatomical differentiation at 4 months and cytological differentiation at 5 months. The ovaries of 24, 36, and 48-month-old grass carp were in the first, second, third, and fourth stages of development, respectively, while the testes were in the second, second, third, and fourth stages of development, respectively. At 48 months of age, the gonads of grass carp have matured. The fluorescence quantitative results showed that the expression level of the female characteristic gene cyp19a1a in the ovary showed an overall trend of first increasing, then decreasing, and then increasing again. The expression level of this gene was significantly upregulated at 2 months of age (P < 0.05), and reached its peak at 3, 6, and 48 months of age. During these three periods, anatomical changes were observed in the female gonads in the tissue sections, with a large proliferation of oocytes and the gonads tending to mature. The expression level of the male characteristic gene amh in the testes showed an overall trend of first increasing and then decreasing. At 2 months of age, the expression level of this gene was significantly upregulated (P < 0.05). At 5 months of age, it reached the peak when there were a large proliferation of spermatogonia in the gonads, and then remained low expression until gonadal maturity.In summary, this study confirmed that the initiation time of grass carp gonadal development is approximately 2 months old, and the differentiation time of male and female gonads is approximately 3 and 4 months old, respectively. By the age of 6 months, both male and female grass carp gonads completely differentiated. These results not only enrich the reproductive physiology data of grass carp but also provide a reference basis for the study of hormone-induced sex reversal technology in grass carp.

Abstract Background Ochratoxin A (OTA) is a toxin widely found in aquafeed ingredients, and hypoxia is a common problem in fish farming. In practice, aquatic animals tend to be more sensitive to hypoxia while feeds are contaminated with OTA, but no studies exist in this area. This research investigated the multiple biotoxicities of OTA and hypoxia combined on the liver of grass carp and explored the mitigating effect of curcumin (CUR). Methods A total of 720 healthy juvenile grass carp (11.06 ± 0.05 g) were selected and assigned randomly to 4 experimental groups: control group (without OTA and CUR), 1.2 mg/kg OTA group, 400 mg/kg CUR group, and 1.2 mg/kg OTA + 400 mg/kg CUR group with three replicates each for 60 d. Subsequently, 32 fish were selected, divided into normoxia (18 fish) and hypoxia (18 fish) groups, and subjected to hypoxia stress for 96 h. Results CUR can attenuate histopathological damage caused by coming to OTA and hypoxia by reducing vacuolation and nuclear excursion. The alleviation of this damage was associated with the attenuation of apoptosis in the mitochondrial pathway by decreasing the expression of the pro-apoptotic proteins Caspase 3, 8, 9, Bax, and Apaf1 while increasing the expression of the anti-apoptotic protein Bcl-2, and attenuation of endoplasmic reticulum stress (ERS) by reducing Grp78 expression and chop levels. This may be attributed to the fact that the addition of CUR increased the levels of catalase (CAT) and glutathione reductase (GSH), increased antioxidant capacity, and ensured the proper functioning of respiratory chain complexes I and II, which in turn reduced the high production of reactive oxygen species (ROS), thus alleviating apoptosis and ERS. Conclusions In conclusion, our data demonstrate the effectiveness of CUR in attenuating liver injury caused by the combination of OTA and hypoxia. This study confirms the feasibility and efficacy of adding natural products to mitigate toxic damage to aquatic animals.

In order to identify biomarkers of lipid deterioration in grass carp (Ctenopharyngodon idella) muscle during cold storage, the lipid profile change of the grass carp muscle stored at 4 ℃ for different periods (3, 6, and 9 d) was investigated by UPLC-Q Exactive HF-X. Multivariate statistical analysis and one-way ANOVA were used to screen the differential lipids during the cold storage, and then to enrich the metabolic pathways involved in the differential lipids through the KEGG database. The results showed that the pH in grass carp muscle decreased gradually, while the thiobarbituric acid reactive substance, total free fatty acid content, and volatile base total nitrogen increased gradually, reaching 0.82 µg/kg, 168.22 µg/10 g and 23.63 mg/100 g, respectively, on the 9 d of cold storage. A total of 1265 lipid molecules belonging to 5 categories and 35 subclasses were identified in the chilled grass carp muscle. Glycerol phospholipids (GP) and glycerol esters (GL) were the main components of lipids in grass carp muscle. There was no significant difference in lipid profile between grass carp muscle refrigerated for 3~6 days (P>0.05), but there were significant changes in lipid composition when refrigerated for 9 days. Fatty acyl (FA) and sphingolipids (SP) were the major different lipids in the early stage of refrigeration (3~6 days), and GP was the main lipids with significant changes in the late stage of refrigeration (6~9 days). A total of 20 different lipid molecules were screened from multivariate statistical difference analysis, and they were mainly glycerol ester and glycerol phospholipid, among which PE (16:1e/22:6) showed significant differences (P

Grass carp was an important economic fish for freshwater aquaculture. The exploring and utilization of high-quality grass carp germplasm resources were important for ensuring a domestic supply of high-quality aquatic protein. However, natural grass carp populations in China were facing severe threats because of the effects of frequent human activities, water environment damage, overfishing, etc. Against this background, high-quality grass carp germplasm resources were the foundation for the healthy and sustainable development of the grass carp aquaculture industry, so systematic collection, preservation, identification, evaluation, protection, and utilization of them carry great strategic importance. This paper summarizes major research results of grass carp in morphology, cytogenetics, molecular population genetics, etc. It not only introduced genetic improvement techniques such as gynogenesis, hybrid breeding, and polyploid breeding, but also discussed the existing research on the protection measures of grass carp germplasm resources. On this basis, the paper proposed new methods to improve the protection of grass carp germplasm and create improved varieties, which could provide high-quality resources for the sustainable development of the grass carp industry.

There are major gaps in illustrating the risk to freshwater fish that are exposed to environmental microplastics (MPs), even though MPs in freshwater environments has drawn much concern. To explore the potentially negative effects of microplastics on freshwater fish, grass carp (averaging 9.215 ± 0.035g) were exposed to microplastics (32–40 μm in diameter) at two environmental concentrations (100 and 1000 μg/L) for 21 days, and evaluated for physio-biochemical performance, gut microbiome, and metabolome responses. After exposure, microplastics were detected in the intestine and within basal nuclei and goblet cells hyperplasia. Antioxidant enzyme activities (superoxide dismutase and catalase) also significantly decreased within the intestines (P

Olfaction, the sense of smell, is crucial for animal survival, especially in localizing prey or food. However, little is known about the fish behavioral responses to specific food odors and which olfactory receptor might be activated by the food odors. Here, we examined the evolutionary relationships and classified the subfamilies of olfactory receptors (ORs), and conducted behavioral and gene expression analysis in grass carp (Ctenopharyngodon idellus). We identified 196 intact ORs in the grass carp genome and classified them into 8 subfamilies: β, δ, ε, η, γ, κ, θ, and ζ. 12 representative ORs (4 β, 4 δ, and 4 ε) were highly expressed in the olfactory epithelium (OE) of 24-month-old grass carp. Behavioral exploration found that grass carp showed different behaviors to different food odors at a series of concentrations. Specifically, 0.01 μmol/L amino acid mixtures and 0.005 × Hydrilla verticillata extracts strongly changed the preference index and swimming trajectories in 6-month-old grass carp. In addition, the two food odors stimulation differentially induced ORs expression in three tissues, especially strong in the olfactory bulb and brain. Altogether, our results suggest that olfaction plays an important role in the regulation of fish feeding behavior and provide a basis for further studies on the function and specific recognition of olfactory receptors in fish.

In nature, aflatoxins, especially aflatoxin B1 (AFB1), are the common mycotoxins, which cause serious health problems for humans and animals. This paper aimed to study the effects of AFB1 on flesh flavor and muscle development of grass carp (Ctenopharyngodon idella) and its mechanism. There were 1440 individual fish in total, with 6 treatments and each treatment replicated 3 times. The 6 treatments were fed a control diet with different doses of AFB1 (0.04, 29.48, 58.66, 85.94, 110.43 and 146.92 μg/kg diet) for 60 d. AFB1 increased myofiber diameter, as well as decreased myofiber density of grass carp muscle (P

Abstract Background The Gα family plays a crucial role in the complex reproductive regulatory network of teleosts. However, the characterization and function of Gα family members, especially Gαq, remain poorly understood in teleosts. To analyze the characterization, expression, and function of grass carp (Ctenopharyngodon idella) Gαq, we identified the Gα family members in grass carp genome, and analyzed the expression, distribution, and signal transduction of Gαq/gnaq. We also explored the role of Gαq in the reproductive regulation of grass carp. Results Our results showed that the grass carp genome contains 27 Gα genes with 46 isoforms, which are divided into four subfamilies: Gαs, Gαi/o, Gαq/11, and Gα12/13. The expression level of Cignaq in the testis was the highest and significantly higher than in other tissues, followed by the hypothalamus and brain. The luteinizing hormone receptor (LHR) was mainly localized to the nucleus in grass carp oocytes, with signals also present in follicular cells. In contrast, Gαq signal was mainly found in the cytoplasm of oocytes, with no signal in follicular cells. In the testis, Gαq and LHR were co-localized in the cytoplasm. Furthermore, the grass carp Gαq recombinant protein significantly promoted Cipgr expression. Conclusions These results provided preliminary evidence for understanding the role of Gαq in the reproductive regulation of teleosts.

Copyright of Science & Technology of Food Industry is the property of Science & Technology of Food Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Ochratoxin A (OTA) is a toxin widely found in aquafeed ingredients, and hypoxia is a common problem in fish farming. In practice, aquatic animals tend to be more sensitive to hypoxia while feeds are contaminated with OTA, but no studies exist in this area. This research investigated the multiple biotoxicities of OTA and hypoxia combined on the liver of grass carp and explored the mitigating effect of curcumin (CUR). Methods: A total of 720 healthy juvenile grass carp (11.06 ± 0.05 g) were selected and assigned randomly to 4 experimental groups: control group (without OTA and CUR), 1.2 mg/kg OTA group, 400 mg/kg CUR group, and 1.2 mg/kg OTA + 400 mg/kg CUR group with three replicates each for 60 d. Subsequently, 32 fish were selected, divided into normoxia (18 fish) and hypoxia (18 fish) groups, and subjected to hypoxia stress for 96 h. Results: CUR can attenuate histopathological damage caused by coming to OTA and hypoxia by reducing vacuolation and nuclear excursion. The alleviation of this damage was associated with the attenuation of apoptosis in the mitochondrial pathway by decreasing the expression of the pro-apoptotic proteins Caspase 3, 8, 9, Bax, and Apaf1 while increasing the expression of the anti-apoptotic protein Bcl-2, and attenuation of endoplasmic reticulum stress (ERS) by reducing Grp78 expression and chop levels. This may be attributed to the fact that the addition of CUR increased the levels of catalase (CAT) and glutathione reductase (GSH), increased antioxidant capacity, and ensured the proper functioning of respiratory chain complexes I and II, which in turn reduced the high production of reactive oxygen species (ROS), thus alleviating apoptosis and ERS. Conclusions: In conclusion, our data demonstrate the effectiveness of CUR in attenuating liver injury caused by the combination of OTA and hypoxia. This study confirms the feasibility and efficacy of adding natural products to mitigate toxic damage to aquatic animals. [ABSTRACT FROM AUTHOR]

Enrofloxacin (EF) is a broad-spectrum and highly efficient antibiotic commonly used for treating diseases in aquatic animals. However, its abuse in aquaculture applications often leads to excess residue in tissues of grass carp (Ctenopharyngodon idella). Hence, this study aimed to estimate the withdrawal time (WT) of EF and its metabolite of ciprofloxacin (CF) administered medicated feed in natural culture environments and conduct a risk assessment. Plasma and tissue samples were gathered at appropriate time points and detected by high-performance liquid chromatography. The data homogeneity was evaluated by Bartlett's test and Cochran's test. The linearity of the regressed line was evaluated by visual inspection and F test. Outliers were estimated on a normal probability scale by plotting the standardized residual versus their cumulative frequency distribution. Finally, the WT was calculated to be 51 days in muscle + skin based on the maximum residue limit of 100 µg/kg. After 51 days, the concentration of EF and CF fell below 10 µg/kg. The estimated daily intake was calculated to be 0.009 µg/kg/d. Hazard quotient was computed to be 0.002, which was far below one. These results suggested that calculated WT of EF could ensure the safety of products from grass carp for humans. [ABSTRACT FROM AUTHOR]

The objective of current study was to evaluate the effect of commercially prepared probiotics (PREPRO) containing Lactobacillus rhamnosus GG on body composition of grass carp (fingerlings). Grass carp is a fresh water fish of edible test and having multiple feed sources. The study was aimed to enhance the production and improve the meat quality of a grass carp in controlled environment. A total of 120 grass carp (fingerlings) were selected and stocked in 12 glass aquaria (n=10 fish in each) in a triplicate manner with four different diet groups D1 (control), D2 (2g of L. rhamnosus/kg), D3 (4g of L. rhamnosus/kg), D4 (6g of L. rhamnosus/kg) as feed additive. Statistical analysis was done by using one-way analysis of variance and was applied the Duncan's multiple range test for the identification of significant differences within the treated groups by using statistical package for the social sciences (SPSS) computer software. After the 90 days of experimental trial the results revealed that probiotics treated groups had significantly (P < 0.05) better meat quality as compared to control. The best meat quality was observed in D4 in terms of crude protein, crude fat, ash content and total moisture (45.86±0.44, 33.59±0.28, 8.80±0.34, 63.98±0.01) compared to control and other tasted groups. The L. rhamnosus improves the meat quality of grass carp. [ABSTRACT FROM AUTHOR]

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Exosomes participate in intercellular communication by carrying proteins, messenger RNA, microRNAs, and non‐coding RNA. Fatty liver is a common phenomenon in farmed fish, but there has been little study of fatty hepatocytes‐derived exosomes. Here, we successfully isolated exosomes from hepatocytes of grass carp, named Exos (hepatocytes‐derived exosomes) and OA‐Exos (fatty hepatocytes‐derived exosomes), from which 617 differentially expressed proteins were identified using liquid chromatography tandem mass spectrometry. Of these, 320 proteins were promoted and 297 proteins were restrained, which were gathered in biological processes and cellular components (cellular processes, cells, and intracellular structures). The results of kyoto encyclopedia of genes and genomes (KEGG) analysis revealed that the differential expression proteins were gathered in "carbohydrate transport and metabolism", "translation, ribosomal structure and biogenesis", "posttranslational modification, protein turnover, chaperones", and "intracellular trafficking, secretion, and vesicular transport". In addition, five differentially expressed exosomal proteins were further confirmed by parallel reaction monitoring, including 2‐phospho‐D‐glycerate hydrolyase, cytochrome b5, fatty acid‐binding protein domain‐containing protein, metallothionein, and malate dehydrogenas, which were downregulated. These findings provided evidence that exosomes derived from fatty hepatocytes of grass carp may be biomarkers for the early diagnosis, treatment, and prevention of fatty liver in fishery development. [ABSTRACT FROM AUTHOR]

In order to explore the effects of NaHCO3 stress on antioxidant enzymes and tissue structure of gill and hepatopancreas of grass carp, three NaHCO3 concentration groups (10, 20, 30 mmol/L) were used to stress grass carp with NaHCO3, and the antioxidant enzymes (SOD, CAT) activity and histopathological observation of gill and hepatopancreas were carried out. The results showed that under NaHCO3 stress, the activities of SOD and CAT in gill and CAT in hepatopancreas of grass carp increased first and then decreased within 72 h, and only the activity of SOD in hepatopancreas increased within 72 h. In each experimental group, the activities of antioxidant enzymes in the two tissues were significantly different from those in the blank group. Compared with the blank group, in the gill tissue of grass carp in the experimental group, the gill filaments were seriously folded and wrinkled, the PVC of the flat epithelial cells was seriously exfoliated, and the MRC of the mitochondria-enriched cells was swollen; in the hepatopancreas, the swelling of the pancreatic cells, the increase of the intercellular space, the deviation of the hepatocyte nucleus and the decrease of the vacuolization were observed. Studies have shown that NaHCO3 stress can affect the antioxidant level of grass carp and cause tissue damage to the gills and hepatopancreas of grass carp, and the degree of damage increases with the increase of concentration. This study could provide reference for the breeding and application of grass carp in saline-alkali waters. [ABSTRACT FROM AUTHOR]

Nutritional value and shelf life of the consolidated burger (grass carp-red meat) during freezing storage at -18 °C was determined in this study. In recent years, with the change in lifestyle and the development of urban life, consuming semi-prepared foods has increased and meat products based on minced meat such as burgers have a major share among these foods in the modern lives. In this study, a combined red meat (beef meat)-grass carp burger with different ratios of 0: 100, 25: 75, and 50:50 was prepared and stored at -18 °C for 4 months. The value of protein, fat, moisture, ash pH, peroxide value, thiobarbituric acid value, volatile nitrogen bases, fatty acid profiles and sensory evaluation were determined on the first day and end of the storage period. Measuring parameters showed the amount of protein, fat, moisture, and ash decreased and the average pH, peroxide, thiobarbituric acid, and volatile basic nitrogen values increased over storage. With increasing the amount of fish meat used in the burger formulation, protein, moisture, ash, and pH values and sensory properties decreased and fat, peroxide, thiobarbituric acid, and volatile nitrogen values increased. The results of this study suggest that consuming Mix50% burger provides some parts of body's needs for unsaturated fatty acids and protein. [ABSTRACT FROM AUTHOR]

Background: The Gα family plays a crucial role in the complex reproductive regulatory network of teleosts. However, the characterization and function of Gα family members, especially Gαq, remain poorly understood in teleosts. To analyze the characterization, expression, and function of grass carp (Ctenopharyngodon idella) Gαq, we identified the Gα family members in grass carp genome, and analyzed the expression, distribution, and signal transduction of Gαq/gnaq. We also explored the role of Gαq in the reproductive regulation of grass carp. Results: Our results showed that the grass carp genome contains 27 Gα genes with 46 isoforms, which are divided into four subfamilies: Gαs, Gαi/o, Gαq/11, and Gα12/13. The expression level of Cignaq in the testis was the highest and significantly higher than in other tissues, followed by the hypothalamus and brain. The luteinizing hormone receptor (LHR) was mainly localized to the nucleus in grass carp oocytes, with signals also present in follicular cells. In contrast, Gαq signal was mainly found in the cytoplasm of oocytes, with no signal in follicular cells. In the testis, Gαq and LHR were co-localized in the cytoplasm. Furthermore, the grass carp Gαq recombinant protein significantly promoted Cipgr expression. Conclusions: These results provided preliminary evidence for understanding the role of Gαq in the reproductive regulation of teleosts. [ABSTRACT FROM AUTHOR]

Simple Summary: Intensive aquaculture decreases immunity and increases diseases that occur in grass carp, which increases economic loss. Hence, improving grass carp immunity is an important strategy for solving the problem of intensive aquaculture. It has been reported that akirin takes part in immune responses. However, the role of akirin in grass carp is unclear. In this study, the akirin gene was isolated from grass carp spleen. The tissue-specific expression of akirin was analyzed. Akirin expression was detected by treatment with LPS, poly (I:C), and A. hydrophila. The immunologic function of akirin proteins was evaluated in HKLs. The findings showed that akirin expression was widely detected in grass carp tissues. Akirin levels were markedly induced via LPS, poly (I:C), and A. hydrophila stimulation in vitro and in vivo. Recombinant grass carp akirin proteins were produced by E. coli. The immune-related genes in HKLs were increased by treatment with recombinant akirin proteins. Intensive aquaculture of grass carp often leads to decreased immunity and increased disease prevalence, resulting in economic losses. Improving grass carp immunity is therefore a critical strategy for addressing these challenges. Akirin reportedly participates in myogenesis, growth, and immune responses. However, its role in grass carp remains unclear. Herein, we isolated akirins from the spleen of grass carp and analyzed their tissue-specific expression. Akirin expression was detected following treatment with poly (I:C), LPS, and Aeromonas hydrophila (A. hydrophila). The immunological function of the akirin protein was evaluated in head kidney leukocytes (HKLs). The results revealed that the coding sequence (CDS) of akirin1 is 570 bp, encoding 189 amino acids. There was one predicted nuclear localization signal (NLS) and two predicted α- helix domains. The CDS of akirin2 is 558 bp, encoding 185 amino acids. There were two predicted NLSs and two predicted α-helix domains. Tissue-specific expression analysis showed that akirins are widely detected in grass carp tissues. akirin1 was highly detected in the brain, kidneys, heart, spleen, and gonads, while akirin2 was highly detected in the brain, liver, gonads, kidneys, spleen, and heart. The mRNA levels of akirins were promoted after treatment with poly (I:C), LPS, and A. hydrophila. Recombinant akirin proteins were produced in Escherichia coli (E. coli). il-1β, ifnγ, il-6, tnfα, il-4, iκbα, and nfκb were markedly increased in grass carp HKLs by treatment with the akirin protein. These results suggest that akirins play a role in the immunological regulation of grass carp. [ABSTRACT FROM AUTHOR]

The hydrodynamics at the fishway entrance play an important role in attracting fish into a fishway. Adjusting the entrance angle of the fishway to allow suitable water flow patterns at the entrance is an effective measure that can be used to improve the attraction efficiency. In this study, we analyzed the movement behavior of grass carp (Ctenopharyngodon idella) in a river channel at a fishway entrance with different fishway entrance angles (30°, 45°, and 60°) and different replenishment velocities (0.1 m/s, 0.2 m/s, and 0.3 m/s). The flow velocity was 0.32–0.50 m/s when the fish head deflected into the entrance under different entrance angles for grass carp. As the entrance angle of the fishway increased, the fish energy consumption increased. The range of energy consumption for grass carp increased from 1.26–3.59 × 10−3 J to 3.32–7.33 × 10−3 J when the entrance angle was increased from 30° to 60°. There was a negative correlation between the entrance angle of the fishway and the deflection angle of the tested fish's head. This research presents a reference that combines fish swimming behavior and hydraulics to optimize the design of fishway entrances. [ABSTRACT FROM AUTHOR]

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This study aimed to explore the effects of different brining times on the sensory, physicochemical properties, and volatile organic compounds (VOCs) of marinated grass carp (MGC). The results showed that different brining time changed the sensory quality, color and texture. The moisture content increased significantly with the extension of brining time, while the salt content, protein content, thiobarbituric acid reactive substances (TBARS), and total volatile basic‑nitrogen (TVB-N) decreased (p