Abstract:

Hemoglobin is a vital component of the circulatory system in higher organisms, and its dysfunction is closely associated with conditions such as anemia and cardiovascular diseases. Antarctic icefish, whose blood appears white due to the absence of functional hemoglobin, serve as a unique model for studying the biological functions of hemoglobin. We identified a conserved non-coding element （CNE） located in the intergenic region chr6：43629743-43629779, upstream of the foxp1b gene, which may play a key role in hemoglobin production in fish. However, its specific regulatory function remains unclear. In this study, we utilized CRISPR/Cas9 gene-editing technology to generate zebrafish heterozygous mutants with knockouts of this CNE. Hemoglobin staining was subsequently performed to compare hemoglobin production between the wild-type control group and the mutant zebrafish. The results demonstrated that the knockout of chr6：43629743-43629779 significantly reduced hemoglobin production in zebrafish. Additionally, qRT-PCR（Quantitative Reverse Transcription Polymerase Chain Reaction） analysis revealed that foxp1b gene expression was significantly lower in the mutant zebrafish compared to the wild-type controls. This study indicates the molecular mechanism by which CNEs regulate hemoglobin production by modulating the expression of downstream genes. It highlights the critical role of conserved non-coding elements in hemoglobin synthesis and offers new insights into the regulation of this essential protein.

Abstract:

Low temperature critically affects the growth, reproduction and disease resistance of warm-water and tropical fishes. Because of climate changes, the effect of low temperatures on fish physiological processes is becoming increasingly pronounced. The molecular mechanism of cold tolerance in fish is a research direction highly relevant to basic life sciences and industrial applications. In this article, the current researches on the molecular mechanism of fish cold tolerance are reviewed from three aspects： physiological and biochemical basis, molecular pathway of responses to signal from low temperature and genetic mapping of cold tolerance traits. When in cold environment, fish will change the composition of fatty acids and enhance the activity of antioxidant enzymes to protect cells from damage, thereby coping with the stress of low temperatures. Meanwhile, the molecular mechanism of fish response to low temperature involves several signal pathways, and the activation and inhibition of these pathways are closely related to the cold tolerance of fish. The molecular mechanisms of cold tolerance in fish has important applications in aquaculture breeding. With advances in genomics technologies, the molecular basis of cold tolerance has been gradually revealed. Gene marker-assisted selection（MAS） and genomic analyses provide essential tools for screening genes related to cold tolerance, facilitating the breeding of cold-resistant fish species. These studies will not only help us understand how fish adapt to environmental changes, but will also open up new ways for the aquaculture industry to address climate changes and improve farming efficiency.

Abstract:

Matrix proteins play a crucial role in regulating the formation of inorganic minerals. In order to investigate the effect of matrix proteins in Hyriopsis cumingii on shell biomineralization, this study isolated a new matrix protein gene cysrichin-F from H.cumingii, and further explored its biological function using techniques such as in situ hybridization, shell-breaking repair and RNA interference （RNAi）. The results showed that the full length of cysrichin-F sequence was 592 bp, and the open reading frame （ORF） region was 42-389 bp, encoding a total of 115 amino acids. The protein encoded by this gene has a theoretical molecular weight of 12.895 ku and a theoretical isoelectric point of 8.65, making it an alkaline protein. The front 23 amino acids of CYSRICHIN-F are signal peptides. Quantitative Real-time PCR （qRT-PCR） detection revealed that the expression level of this gene in the mantle was relatively high compared to other tissues. Through in situ hybridization and shell-breaking repair techniques, it was found that cysrichin-F was involved in the formation of the cuticle and prismatic layers of shells. After interference with this gene, the structure of the shell prismatic layer would be disrupted, ultimately resulting in an irregular shape of the shell prismatic layer. This study showed that cysrichin-F was involved in the biomineralization process of the cuticle and prism layers of shells. The results of the study can help to elucidate the molecular mechanism of the biomineralization in H.cumingii, and provide a theoretical basis for the role of matrix proteins in the formation of shells in H.cumingii.

Abstract:

Intermuscular bone （IB） is one of three morphological characters of teleosts, and is becoming an obstacle for fish processing. Recently, some cyprinid fish without IB have been generated by Crispr/Cas9 technology, will be very helpful for our fresh fish culture in China. So far bmp6 and runx2b have been determined as key genes for the development of IBs, however, upstream signal pathway to regulate the development is not sure, and the complex evolution of IBs in teleost is in lack of understanding. This review first gives us a basic introduction on the IB types, distribution, and the role in swimming, then focuses on the research advance on IB developmental model, cellular origin, and upstream regulation factors. Finally, a preliminary hypothesis is proposed in this review to explain IB evolution in teleosts, indicating IB evolution potential associations between axial muscle diversification and locomotion adaptive radiations that generated modern teleost lineages.

Abstract:

In this study, an expressed sequence tag （EST） belonging to the α-type carbonic anhydrase （CA） was identified from the transcriptome database of Saccharina japonica gametophytes. This sequence shares 68.02% and 77.32% similarity with previously reported α-CA family members in S. japonica, namely Sjα-CA1 and Sjα-CA2, suggesting that it might be a new member of the α-CA family, designated as Sjα-CA3. Using RACE technology, the full-length cDNA sequence of Sjα-CA3 was obtained, measuring 1469 bp in total and comprising an 840 bp open reading frame （ORF）, a 332 bp 5'-untranslated region （UTR）, and a 297 bp 3'-UTR. The Sjα-CA3 gene encodes a protein of 279 amino acid residues with a theoretical molecular weight of 31.19 kDa and an isoelectric point of 4.85. Multiple sequence alignments indicate that the functional sites of Sjα-CA3 are highly conserved. Phylogenetic analysis shows that Sjα-CA3 clusters with α-CA proteins from other algae with high confidence （99/81, NJ/ML）, further supporting its classification within the α-CA family. A pET32a-SjαCA3 prokaryotic expression vector was constructed through heterologous recombination technology and introduced into E. coli BL21 （DE3） competent cells. Following induction and purification, a recombinant protein （rSjα-CA3） with an approximate molecular weight of 45 ku was obtained. Enzyme activity assays revealed that rSjα-CA3 exhibits both hydration and esterase activities, with specific activities of 0.82 U/mg protein and 2.157 U/g protein, respectively. The successful isolation and identification of Sjα-CA3 provide crucial data for further analysis of its role in the inorganic carbon storage mechanism in S. japonica, as well as for advancing studies on the carbon concentrating mechanism （CCM） in this kelp.

Abstract:

Phytoplankton is an important primary producer of water, and its functional group characteristics play an important role in maintaining the stability of aquatic ecosystems. In order to reveal the characteristics and construction mechanism of phytoplankton functional group community and its driving factors in river networks of megacity, 19 representative small and medium-sized rivers in Shanghai were selected to investigate the characteristics of phytoplankton functional groups and environmental factors at 40 sites. The results showed that a total of 175 species of phytoplankton in 8 phyla were identified, which could be divided into 23 functional groups, and B, D, J, MP, P, S1, X1, X2, X3 and Y were the dominant functional groups. The results of cluster analysis showed that 40 sampling sites could be divided into two characteristic groups： low nutrient （G1） and high nutrient （G2）. There were significant differences in Shannon-Wiener diversity index, Margalef index, phytoplankton functional group community structure and environmental factors between the two groups （P<0.05）. The modified stochasticity ratio （MST） and the decay relationship analysis showed that the community construction of phytoplankton functional groups in Shanghai River was affected by the environmental filtering and spatial diffusion limitation, and the stochastic process was dominant. The community construction of the low nutrient group （G1） was affected by environmental filtration, while the spatial diffusion affected the construction of phytoplankton functional groups in the higher nutrient group （G2）. Difference analysis and multiple regression analysis showed that total nitrogen, nitrite nitrogen, total phosphorus, conductivity and dissolved oxygen were the main environmental factors affecting the community structure of phytoplankton functional groups in Shanghai River. This study provides new information for in-depth understanding of the biodiversity and ecological function maintenance mechanism of river networks in megacities, as well as the protection of water ecosystems in urban river networks.

Abstract:

To study the impact of ferric ions on the ability of Shewanella marisflavi ECSMB14101 biofilms to induce larval settlement and metamorphosis in Mytilus coruscus, single bacterial biofilms cultivated with different ferric ion concentrations were used to induce larval settlement and metamorphosis. The effects of ferric ion concentration on the inducing activity of larval settlement and metamorphosis, bacterial density, extracellular polymeric substances, and cytochrome C content of S. marisflavi biofilms were analysed. Results showed that among the seven groups with ferric ion concentrations of 0, 1, 10, 20, 30, 40, and 50 μmol/L, the biofilm of S. marisflavi cultivated at a concentration of 20 μmol/L exhibited the highest inducing activity. Furthermore, at this concentration, both the bacterial density of the biofilm and the levels of extracellular proteins and cytochrome C reached their peak among all seven tested concentrations. Extracellular polysaccharides and lipids were not significantly affected by ferric ion concentration. It was shown that under the effects of ferric ions, S. marisflavi biofilms regulate the larval settlement and metamorphosis in M. coruscus by modulating the production of extracellular proteins, including cytochrome C. This research offered a solid theoretical foundation and served as a valuable reference for the in-depth investigation of the molecular regulatory mechanisms underlying larval settlement and metamorphosis in M. coruscus. Additionally, it contributes to the understanding of interactions between shellfish and bacteria.

Abstract:

This experiment was designed to investigate the effects of dietary different concentrations of mulberry leaf polysaccharide （MLWE） on the growth performance, hepatopancreas immune indicators, antioxidant capacity, and intestinal health of Macrobrachium rosenbergii juveniles. The basal diet without mulberry leaf extract was used as the control group （MLWE0）, and on this basis, 3 g/kg （MLWE3 group）, 6 g/kg （MLWE6 group）, 9 g/kg （MLWE9 group） and 12 g/kg （MLWE12 group） of mulberry leaf extract were added to the basal diet to prepare five groups of isonitrogenous and isolithiatic diets, respectively. The healthy and active larvae of M. rosenbergii juveniles with initial body weight of （0.75±0.09）g were selected as the research objects. Each experimental group was set up with 3 replicates, and the experimental period was 56 days. The results indicated that： In comparison with the control group, the final average weight, specific growth rate and weight gain rate of the MLWE6, MLWE9, and MLWE12 groups increased significantly （P<0.05）, on the contrary, there was lower feed conversion ratio in MLWE6, MLWE9, and MLWE12 groups than that of the control group （P<0.05）. With the increase of MLWE supplemental level in dietary, the thickness of intestinal muscle layer decreased in groups of MLWE3, MLWE6, and MLWE9, while there was an increase in height and width of intestinal folds compared with the control group. Although there were no notable changes in intestinal microvilli height between the control group and treatment groups, high density of intestinal microvilli was observed on experimental group. Significantly lower levels （P<0.05） for malondialdehyde （MDA）, superoxide dismutase （SOD）, catalase （CAT）, and glutathione peroxidase （GSH-Px） were observed on the experimental groups compared to the control group, in addition, compared to the control group, there were higher expression levels of immune-related gene in hepatopancreas of prawn fed diets with 6 and 9 g/kg mulberry leaf water extract （P<0.05）, the relative abundance of pathogenic bacteria （such as Aeromonas hydrophila and Vibrio cholera） in the intestinal microbiota of M. rosenbergii juveniles was significantly reduced in the MLWE6, MLWE9, and MLWE12 groups （P<0.05）. In conclusion, adding appropriate concentrations of MLWE to the basic diet of M. rosenbergii juveniles can promote their growth, enhance their non-specific immunity, and improve gut health. Based on the comprehensive analysis and the index of weight gain rate, it is suggested that the appropriate addition level for mulberry leaf water extract in the diet of M. rosenbergii juveniles is between 6 and 9 g/kg.

Abstract:

In this study, we cloned the TAP1, TAP2a, and TAP2t genes from grass carp （Ctenopharyngodon idella）, and analyzed their phylogeny. It was found that grass carp TAP genes are conserved. Structural prediction of TAP proteins revealed that grass carp TAP proteins possess multiple transmembrane regions and have typical structural features of the ATP-binding cassette transporter （ABC） superfamily. Grass carp TAP1, TAP2a, and TAP2t genes were highly expressed in the spleen and kidney, and significantly up-regulated at 72h after infection with Aeromonas hydrophila. In the primary head kidney leukocytes, stimulation with phytohemagglutinin （PHA） and polyinosinic-polycytidylic acid [poly（I： C）] up-regulated all TAP genes, and that with interferon gamma （IFN-γ） and interleukin 1 beta （IL-1β） induced the expression of TAP1 and TAP2t but not TAP2a. In the EPC cells, infection with Spring viraemia of carp virus （SVCV） elevated the expression levels of TAP1 at 12 h, 24 h, and 36 h and TAP2t at 12 h, suggesting they are involved in immune response to SVCV infection. The findings provide valuable information for further investigation on MHC I antigen presentation pathway in fish.

Abstract:

To explore the antibacterial activity and structural composition of rhamnolipids produced by Pseudomonas aeruginosa A39-1 fermentation with various carbon sources, as well as to analyze the rhamnolipid biosynthesis process, the inhibitory activity of rhamnolipids against pathogens was determined using the Oxford cup assay, the congener composition of rhamnolipid samples was detected and analysed using liquid chromatography-mass spectrometry （LC-MS）, and the whole genome sequence was determined and assembled using Illumina Hiseq and PacBio. Genome sequence annotated and analysed rhamnolipid synthesis-related genes. Rhamnolipids produced by strain A39-1 by fermentation with glycerol, glucose, sunflower oil, rapeseed oil and blended oil as the sole carbon source had antibacterial activity； LC-MS detection of rhamnolipids obtained by glycerol fermentation as four monosaccharide monolipids （Rha-C_8∶2, Rha-C_9∶2, Rha-C_11∶2, Rha-C₁₀） and four monosaccharide bilipids （Rha-C_6∶1-C_6∶1, Rha-C_12∶1-C_12∶1, Rha-C₁₂-C₁₄, Rha-C_14∶2-C_14∶2）, Rha-C_11∶2 is the primary structure； The genome was anticipated to have genes for rhamnolipid synthesis related to algC, rmlA, rmlB, rmlC, rmlD, rhlA, rhlB, as well as the absence of gene rhlC encoding rhamnosyltransferase II synthesizes bi-rhamnolipids. Pseudomonas aeruginosa A39-1, a wild-type strain with a natural rhlC gene deletion, produced mono-rhamnolipids exclusively by fermentation with different carbon sources, and the mono-rhamnolipids had antibacterial activity. This study explores the antibacterial activity of mono-rhamnolipids, analyzes composition and biosynthesis pathways, and provides new ideas for the development of new green prevention and control medicines for aquatic animal diseases.

Abstract:

To investigate the effects of low-temperature stress on the antioxidant and non-specific immune capacity of crayfish （Procambarus clarkii）, we collected hepatopancreas, gills and haemolymph at 4 temperature levels （control： 23 ℃, experimental group： 9 ℃, 5 ℃, 1 ℃）, then measured antioxidant and immune-related enzyme activities and gene expression. The results of antioxidant and immunoenzymatic activities showed a gradual increase in total antioxidant capacity （T-AOC） activity in hepatopancreas and haemolymph of P. clarkii under low temperature stress. The trend of increasing and then decreasing activities of superoxide dismutase （SOD）, glutathione peroxidase （GSH-PX）, acid phosphatase （ACP） and alkaline phosphatase （AKP） was observed in hepatopancreas and haemolymph. Both malondialdehyde （MDA） contents increased gradually, peaking at 1 ℃. Catalase （CAT） decreased gradually in the hepatopancreas with an increase followed by a decrease in the haemolymph. Gene expression results showed that mRNA expression of SOD, CAT, and Crustin genes in gills and hepatopancreas of P. clarkii increased and then decreased with decreasing temperatures under low-temperature stress,and the heat shock protein 70 （HSP70） gene mRNA expression does not change significantly in gills with an increase followed by a decrease in hepatopancreas. In summary, oxidative stress occurred in P. clarkii under low-temperature stress, and the antioxidant and immune system responded to low-temperature oxidative damage by increasing the activity of antioxidant and immune enzymes and inducing the high expression of antioxidant and immune genes, to protect cellular activity and maintain normal life activities. The results of this study provide a theoretical basis for the selection and breeding of low temperature resistant strains of P. clarkii under the integrated rice-crayfish aquaculture model.

Abstract:

Agonistic behavior is a common phenomenon in the culture of Eriocheir sinensis. To explore the adverse effects of loser experience, anxiety-like behavior and feeding behavior of E. sinensis after loser experience were observed, and the levels of serotonin （5-HT） and 5-HT7R gene relative expression were detected. Then, the effects of exogenous 5-HT, fluoxetine, and 5-HT7R agonists and antagonists on the anxiety-like behavior of E. sinensis were observed. The results indicated that the E. sinensis that experienced the fight failure showed anxiety-like behavior, which was accompanied by the increase of plasma 5-HT concentration and the decrease of 5-HT7R gene relative expression level in the thoracic ganglion, and the food intake decreased after the loser experience. Exogenous 5-HT treatment promoted anxiety-like behavior, while fluoxetine treatment alleviated anxiety-like behavior. In addition, treatment with 5-HT7R agonist （AS19） promoted anxiety-like behavior, while treatment with 5-HT7R antagonist （SB-269970） alleviated anxiety-like behavior. These results indicate that the loser experience can lead to anxiety-like behavior and affect anxiety-like behavior through the serotonin pathway. This study revealed the potential negative effects of loser experience and provided theoretical basis for promoting healthy culture of E. sinensis.

Abstract:

The distant-water fishery, a crucial part of the marine economy, is currently facing a historic opportunity for transformation and upgrading. Based on the theoretical framework of new quality productivity, this article delves into the concept, connotation, and important role of new quality productivity in China's distant-water fisheries. Through a comprehensive analysis of the current situation and challenges of the distant-water fishing industry, this article proposes five specific suggestions and countermeasures on how to develop new quality productivity in the distant-water fishing industry. The first is to strengthen the scientific and technological innovation of the equipment and technology of distant-water fishery to enhance the level of intelligence. The second is to optimize the industrial structure of distant-water fishery to promote diversified development. The third is to strengthen conservation of distant-water fishery resources to achieve sustainable use of resources. The forth is to deepen international fisheries cooperation to expand space for development of distant-water fisheries. The fifth is to increase the policy support of distant-water fisheries to stimulate the vitality of development. The study concluded that the development of new qualitative productivity of distant-water fisheries is an inevitable choice to promote high-quality development of our country's distant-water fisheries, and is a long-term and arduous task and systems engineering. The scientific and technological innovation and optimization of industrial structure are the core of new qualitative productivity of pelagic fisheries, and strengthening conservation of fishery resources, deepening international cooperation and increasing policy support are the important guarantee of new qualitative productivity of pelagic fisheries.

Abstract:

To address the limitations of traditional habitat prediction models in capturing the lagged effects of environmental factors with time series information on tuna spatial distribution, this study utilized tuna purse-seine fishing log data from 2021 to 2024. Long-short term memory （LSTM） neural network models were constructed with lag durations of 1 day, 5 days, 10 days, and 15 days to predict catch per unit of effort （CPUE） and geographic coordinates （latitude and longitude）.The findings indicate that the 10-day lag model exhibited the highest accuracy, with a mean square error （MSE） of 0.018 7 and a mean absolute error （MAE） of 0.077 6, suggesting that the spatial distribution of skipjack is influenced by cumulative short-term environmental effects. Validation of the optimal model demonstrated the R² of 0.97 for predicted versus actual latitude and 0.65 for longitude, indicating a strong alignment between predicted and observed spatial distributions.This research offers new insights into the dynamic mechanisms underlying skipjack tuna habitat characteristics and ecological processes. Furthermore, it provides critical references for the scientific management of skipjack purse seine fisheries in the Western and Central Pacific Ocean.

Abstract:

Fish body morphology contains important ecological information and is a valuable feature for species identification and population classification. There are many kinds of fish in Northwest Pacific Ocean, making the study of fish biodiversity a significant challenge in the study of fish morphology. At present, the study of fish species identification by using fish body geometric morphometrics is relatively lacking, and the classification effect of different fish body parts morphology is necessary to be discussed. In order to understand the morphological structural diversity of important fish species in Northwest Pacific Ocean, and effectively improve the efficiency of fish species identification in this area. In this study, the morphologies variation of 485 tails of 26 species from 24 genera, 14 families and 8 orders in Northwest Pacific Ocean were constructed based on landmarks data and geometric morphometrics, and the taxonomic effects of different body morphological parameters on species recognition were evaluated. The results showed that there were significant differences in fish body morphology among different orders and species. In addition, Multiple regression analysis （MRA） detected allometry in some species. In terms of classification, and the body and torso shape could be better distinguished from different species. Studies have shown that fish species in Northwest Pacific Ocean have a variety of body shape structures, and the heterogeneity of the life history of different species and genetic factors may be the reasons for the body diversity. This study can improve the fish taxonomy in Northwest Pacific Ocean and provide a scientific basis for the sustainable development and effective resource management of fish species in Northwest Pacific Ocean. Future studies can add more species and numbers in order to explore more universal morphological differences and taxonomic effects.

Abstract:

The aquaculture net cage is an important farming equipment that enhances the efficiency of marine area utilization, promotes the sustainable development of fisheries, and provides abundant and high-quality aquatic products. Mooring system is the key to ensure the safe and stable operation of aquaculture cages. This paper systematically summarizes the research status of structural design, theoretical analysis, hydrodynamic simulation and prototype test of cage mooring system. The structure and combination of mooring system for aquaculture cages are summarized. The performance of taut mooring system, catenary mooring system, single-point mooring system, multiple-points mooring system and grid mooring system are compared and analysed from perspectives of anchor cable tension requirements, positioning accuracy, load capacity, fatigue life, cage movement, anchor cable stress, pool experiments, and marine measurements. The design framework of aquaculture cage mooring system is formed. The research results provide theoretical and technical reference for the design and optimization of aquaculture cage mooring system, and point out the future development direction.

Abstract:

In order to solve the problems of insufficient accuracy of fish target recognition in complex underwater environment, high complexity and slow recognition speed of traditional target recognition models, an underwater fish target recognition model based on improved YOLOv8n-fish was proposed. In this paper, a lightweight double-convolutional module C2f-DualConv is proposed to improve the feature learning ability of the C2f module in YOLOv8n. Based on the idea of efficient structure reparameterization, a new neck network EffQAFPN was designed to balance the recognition accuracy and speed of the target model. A two-stage fine-tuning method was used to improve the recognition accuracy of the fish target recognition model in the underwater low light and interference environment. The experimental results show that the average accuracy of the YOLOv8n-fish model in the test set is 97.47%, which is 1.07% higher than that of the traditional YOLOv8n model. However, the number of parameters, floating-point arithmetic and model memory occupation of the improved model are only 56.1%, 82% and 66.7% of the original model. The recognition speed of the YOLOv8n-fish model is second only to that of YOLOv5n-P6, which can reach 121 f/s. Experimental results show that the YOLOv8n-fish model can significantly reduce the computational cost while maintaining high recognition accuracy, and provide effective technical support for intelligent monitoring of aquaculture.

Abstract:

Ultrasound-assisted freezing （UAF） technology is commonly used in the freezing preservation of large yellow croaker （Larimichthys crocea）. In order to improve the quality of frozen large yellow croaker, this study introduced orthogonal mode on the basis of UAF. A novel technique of Triple-frequency orthogonal ultrasound assisted freezing （TOUAF） was developed. In order to explore the effects of different power TOUAF on the quality of frozen large yellow croaker, the thawing loss, water retention, low field nuclear magnetic resonance （LF-NMR） and magnetic resonance imaging （MRI）, chromatic difference, texture properties, TBA, protein solubility and surface hydrophobicity were measured after TOUAF treatment with different powers （160 W, 175 W, 190 W, 205 W）. The results showed that TOUAF-175 could significantly increase water retention （79.450%±1.571%）, reduce thawing loss （2.343%±0.044%） and water migration. The low TBA value of TOUAF-175 [（0.108±0.014） mg MDA/kg] indicated that TOUAF-175 effectively inhibited lipid oxidation. At the same time, TOUAF-175 has better effects than other power groups in terms of color difference, texture properties, improving protein solubility and reducing surface hydrophobicity. However, the quality of the frozen samples in the treatment group with higher power decreased due to the release of latent heat and mechanical damage to the frozen samples. The study showed that proper power of TOUAF could effectively reduce the damage of frozen fish tissue and improve the quality of frozen large yellow croaker. TOUAF-175 is an effective method to promote the freezing process and improve the quality of frozen large yellow croaker.

Abstract:

Freezing is a common method of food preservation, but the traditional freezing method causes the formation of a large number of irregular ice crystals, which affects the taste and nutritional value of aquatic products. In this study, a static magnetic field-assisted freezing system based on an impact freezer was established to improve the freezing quality and reduce the adverse effects of freezing on aquatic products. The effects of static magnetic fields with different intensities （20 Gs, 40 Gs, 60 Gs, and 80 Gs） on the moisture distribution and physicochemical properties of frozen Penaeus japonicus were investigated. The results showed that the static magnetic field-assisted freezing technique shortened the phase transition time, and the higher the magnetic field intensity, the shorter the phase transition time. In terms of moisture distribution, the magnetic field-assisted freezing technique significantly reduced the thawing loss, cooking loss, and centrifugal loss. Among them, the cooking loss and centrifugal loss of the SMF-80 group were not significantly different from those of the fresh group, indicating that the magnetic field-assisted freezing can effectively reduce moisture loss of Penaeus japonicus. LF-NMR showed that the static magnetic field reduced the mobility and loss of fixed and free water. In addition, the static magnetic field accelerated the freezing rate and suppressed the increase of L* value in shrimp samples, and the DSC analysis showed that the thermal stability of of Penaeus japonicus proteins increased, indicating that the application of static magnetic field could reduce the damage to the protein structure.The static magnetic field also significantly improved the hardness, chewiness and resilience of Penaeus japonicus after freezing and thawing, and enhanced the texture of Penaeus japonicus. In conclusion, the static magnetic field-assisted freezing system effectively improved the quality of frozen Penaeus japonicus and minimized the adverse effects of freezing on the nutritional value of Penaeus japonicus.

Abstract:

Heavy metal is a typical persistent pollutant, which can enter organisms through various ways such as respiration, drinking water and food chain transmission, and can be circulated among plants, animals, microorganisms and humans. At the same time, with the transfer of heavy metals and the transformation of valence or form, heavy metals with different valence or form may have significant toxicity differences and produce typical toxic effects on organisms. In food production, raw materials, processing, and human digestion and metabolism may cause changes in the valence, morphology, and total amount of heavy metals, thereby significantly affecting their toxicity. At present, in the risk assessment of heavy metals in food, the risks caused by changes in their morphology or valence are ignored. This paper reviews the risks caused by the transfer and transformation of heavy metals in the food industry chain, which is of great significance for the scientific assessment of the toxicity of heavy metals entering the human body through the food chain, especially the heterogeneous hazards of heavy metal in the process of transfer and speciation or valence transformation, in order to provide theoretical guidance for the scientific assessment of heavy metal pollution in food.

Abstract:

Salmon is popular among consumers because of its rich nutrition and tender taste, but it is easy to be contaminated by microorganisms during processing and storage, resulting in nutrient loss and tissue structure destruction. In this study, curcumin was used as photosensitizer to preserve salmon by Photodynamic technology （PDT）. The bacteriostatic efficiency of curcumin-mediated photodynamics was investigated by detecting the proliferation of microorganisms in salmon treated with PDT, and the mechanism of PDT to guarantee the quality of salmon was preliminatively explored from the perspective of color difference, endogenous enzyme activity, tissue slices and water migration. The results showed that 150 μmol/L curcumin combined with light treatment for 1 h could effectively kill 1.6 log₁₀CFU/g microorganisms in salmon. In addition, curcumin-mediated PDT significantly inhibited the activity of ATPase and lipase in salmon, delayed the degradation of free amino acids and free fatty acids, thus guaranteeing the structural integrity and moisture content of salmon, and extended its shelf life by 2 d. This study can provide data and theoretical support for the photodynamic technology to guarantee the quality of salmon, and promote its practical application in the field of food preservation.