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Clarifying the biosynthetic pathway of the long-chain polyunsaturated fatty acids (LC-PUFA) of Sinonovacula constricta is essential for utilizing its LC-PUFA resources. Methyl-end (or "ωx") desaturases are the rate-limiting enzymes in LC-PUFA biosynthesis, catalyzing the conversion of oleic acid to linoleic acid (LA) or LA to α-linolenic acid. However, their presence in S. constricta remains uncertain. Herein, we identified two ωx desaturase-like genes within the S. constricta genome, both located on the ninth chromosome possibly due to genome duplication. These genes exhibited nearly identical sequences, differing by only one amino acid, and each encodes a 354-residue peptide with typical ωx desaturase characteristics. Phylogenetic analysis grouped these putative ωx desaturases with similar enzymes from other invertebrates. However, when heterologously expressed in yeast, they exhibited no detectable desaturation activity. This suggests either non-functionality in yeast or extremely subtle desaturation abilities. Additionally, both genes displayed the highest expression in the inhalant siphon rather than in digestive tissues and exhibited relatively high expression throughout the development stages of S. constricta, except in zygotes. These findings suggest potential in vivo functional roles for these ωx desaturases in S. constricta. Collectively, these results significantly enrich our understanding of the repertoire of LC-PUFA biosynthetic enzymes in this important bivalve species. [ABSTRACT FROM AUTHOR]

The razor clam Sinonovacula constricta, a commercially important and nutritionally valuable bivalve species, has been found to display notable responses to different light spectra. While previous research has highlighted the influence of light spectra on the growth, feeding rate, and various physiological characteristics of S. constricta, its impact on the biochemical composition of this species remains unclear. Herein, we investigated the proximate, fatty acid, and amino acid compositions of S. constricta cultured under various light spectra, including white, violet, blue, cyan, green, yellow, red, and darkness. Furthermore, we explored the potential molecular mechanisms underlying these observations through transcriptomic analysis. The results indicate that the light spectrum has a significant impact on the growth, biochemical composition, and gene expression of juvenile S. constricta. Specifically, culturing S. constricta under the yellow light led to improved growth rate (1.09 ± 0.03%/day), higher levels of carbohydrate (26.27% ± 0.49%), crude lipid (11.99% ± 0.23%), energy contents (14,611.34 ± 1,067.01 kJ/kg), and essential amino acids (15.22 ± 0.01 g/kg), as well as increased proportions of polyunsaturated fatty acids (12.38 ± 0.31 µg/mg). These findings suggest that yellow light may play a crucial role in enhancing the nutritional quality of S. constricta. Moreover, the transcriptomic analysis revealed that the yellow light treatment upregulated pathways related to fatty acid biosynthesis, glycine, serine, and threonine metabolism and fatty acid metabolism. This indicates that yellow light may influence nutrient metabolism regulation in S. constricta, potentially leading to the observed changes in biochemical composition. Overall, our study recommends cultivating juvenile S. constricta under yellow light to optimize their growth and nutritional value. Further research could delve deeper into the molecular mechanisms underlying the effects of different light spectra on S. constricta to enhance our understanding of how light influences aquaculture practices and the nutritional quality of seafood products. [ABSTRACT FROM AUTHOR]

Gamma-aminobutyric acid (GABA), widely existing in different organisms, is rapidly accumulated in plants in response to environmental stresses. The main biosynthesis and degradation pathways of GABA constitute the GABA shunt, which is tied to the tricarboxylic acid (TCA) cycle. GABA transaminase (GABA-T) and succinate semialdehyde dehydrogenase (SSADH) are two essential enzymes for the GABA degradation pathway. While there are abundant studies on GABA shunt in higher plants at the physiological and genetic levels, research on its role in microalgae remains limited. This study aimed at exploring the function of GABA-T and SSADH genes in Isochrysis zhanjiangensis, an important diet microalga, under different stresses. We cloned two GABA-T genes, IzGABA-T1 and IzGABA-T2, and one SSADH gene IzSSADH from Isochrysis zhanjiangensis and conducted heterologous expression experiments. The results showed that the overexpression of IzGABA-T1 or IzGABA-T2 enhanced the survival rates of yeast transformants under heat or NaCl stress, while the overexpression of IzSSADH improved yeast tolerance to NaCl stress but had no obvious effect on heat stress. Additionally, the results of quantitative real-time polymerase chain reaction (qPCR) showed that IzGABA-T1 transcription increased in the HT (salinity 25, 35°C) and LS (salinity 15, 25°C) groups. At 24 h, the IzGABA-T2 transcriptions increased in the HT, LS, and HS (salinity 35, 25°C) groups, but their transcription levels decreased in all groups at 48 h. IzSSADH transcription increased in the LS group. These results suggest that IzGABA-T1, IzGABA-T2, and IzSSADH are associated with temperature and salinity stresses and possess a certain preference for different stresses. [ABSTRACT FROM AUTHOR]

Summary: Fucoxanthin, a natural carotenoid that has substantial pharmaceutical value due to its anticancer, antioxidant, antiobesity, and antidiabetic properties, is biosynthesized from glyceraldehyde‐3‐phosphate (G3P) via a series of enzymatic reactions. However, our understanding of the transcriptional mechanisms involved in fucoxanthin biosynthesis remains limited.Using reverse genetics, the med8 mutant was identified based on its phenotype of reduced fucoxanthin content, and the biological functions of MED8 in fucoxanthin synthesis were characterized using approaches such as gene expression, protein subcellular localization, protein–protein interaction and chromatin immunoprecipitation assay.Gene‐editing mutants of MED8 exhibited decreased fucoxanthin content as well as reduced expression levels of six key genes involved in fucoxanthin synthesis, namely DXS, PSY1, ZDS‐like, CRTISO5, ZEP1, and ZEP3, when compared to the wild‐type (WT) strain. Furthermore, we showed that MED8 interacts with HSF3, and genetic analysis revealed their shared involvement in the genetic pathway governing fucoxanthin synthesis. Additionally, HSF3 was required for MED8 association with the promoters of the six fucoxanthin synthesis genes.In conclusion, MED8 and HSF3 are involved in fucoxanthin synthesis by modulating the expression of the fucoxanthin synthesis genes. Our results increase the understanding of the molecular regulation mechanisms underlying fucoxanthin synthesis in the diatom P. tricornutum. [ABSTRACT FROM AUTHOR]

The primary cause of tool failure in rough cutting is the severe tool-chip friction brought on by chip adhesion and abrasive wear. To address the problem, the influence of combinations of micro-textures and AlCrN coating, and the sequence of their combinations on tool surface characteristics and cutting performance in dry cutting AISI 304 were investigated. The results of wettability and indentation tests indicate the micro-textures reduce the contact angle of the tool surface (by 13.26%) and increase the contact area between micro-textures and the coating, resulting in a better adhesive strength (grade HF3) for the first micro-textured and then AlCrN-coated tool (TCT). The results of cutting experiments demonstrate that the TCT's cutting performance is improved as the cutting speed increases between 50 and 141 m/min, with the highest reductions in main cutting force and radial cutting force reaching 27% and 38% at 141 m/min. The TCT's micro-textures reduce tool-chip contact area, while the intact AlCrN coating film decreases chip adhesion and improves the wear resistance of cutting tools. This study is expected to be applied to further improve the tool performance under dry and rough cutting conditions. [ABSTRACT FROM AUTHOR]

The morphology of the molten pool plays a crucial role in determining the surface quality of components during laser polishing of 304 stainless steel. Lens ultrasonic vibration significantly impacts the formation of the molten pool during ultrasonic vibration-assisted laser polishing. In this paper, experimental and numerical simulations were applied to investigate the surface properties of ultrasonic vibration-assisted laser polishing. A comparison was conducted between traditional laser polishing and ultrasonic vibration-assisted laser polishing in terms of the difference in peak temperature of the molten pool. The molten pool morphology obtained from the simulation is compared with the experiment results to verify the accuracy of the established model. Consequently, the model exhibits high precision and versatility, allowing for flexibility applied to laser polishing of other systems or materials. The dynamic changes of the temperature field, force field, and velocity field in the molten pool were discussed in detail to reveal the mechanism by which ultrasonic vibration influences. This research work contributes to understanding and guiding the surface formation during ultrasonic vibration-assisted laser polishing of 304 stainless steel. [ABSTRACT FROM AUTHOR]

The razor clam Sinonovacula constricta is the first marine mollusk demonstrated to possess the complete long-chain polyunsaturated fatty acids (LC-PUFA) biosynthetic pathway. This study explored the impact of different microalgae on growth, Fad and Elovl expressions, and fatty acid (FA) profiles in juvenile S. constricta. Results revealed that juveniles fed with Isochrysis galbana (rich in DHA) or Chaetoceros calcitrans (rich in EPA) consistently exhibited higher growth than those fed Chlorella sp. (rich in LA and ALA), underscoring the importance of dietary LC-PUFA in S. constricta's development. Expression of most Fad and Elovl in C. calcitrans and I. galbana-fed juveniles were initially up-regulated, then down-regulated, suggesting LC-PUFA demand for faster growth. Although Chlorella sp.-fed juveniles exhibited decreased mRNA levels for most genes, levels were notably higher lately compared to those fed C. calcitrans or I. galbana, hinting at potential LC-PUFA biosynthesis induction. FA profiles in S. constricta generally mirrored those in ingested microalgae, implying direct FA accumulation from diets. Some microalgal FA were absent in farmed S. constricta, while others emerged, indicating S. constricta's ability to selectively accumulate and synthesize FA. This study enhances the understanding of dietary FA metabolism in S. constricta, valuable for selecting appropriate microalgae in its farming practices. [ABSTRACT FROM AUTHOR]

Attribute reduction is a crucial research area within concept lattices. However, the existing works are mostly limited to either increment or decrement algorithms, rather than considering both. Therefore, dealing with large-scale streaming attributes in both cases may be inefficient. Convolution calculation in deep learning involves a dynamic data processing method in the form of sliding windows. Inspired by this, we adopt slide-in and slide-out windows in convolution calculation to update attribute reduction. Specifically, we study the attribute changing mechanism in the sliding window mode of convolution and investigate five attribute variation cases. These cases consider the respective intersection of slide-in and slide-out attributes, i.e., equal to, disjoint with, partially joint with, containing, and contained by. Then, we propose an updated solution of the reduction set for simultaneous sliding in and out of attributes. Meanwhile, we propose the CLARA-DC algorithm, which aims to solve the problem of inefficient attribute reduction for large-scale streaming data. Finally, through the experimental comparison on four UCI datasets, CLARA-DC achieves higher efficiency and scalability in dealing with large-scale datasets. It can adapt to varying types and sizes of datasets, boosting efficiency by an average of 25%. [ABSTRACT FROM AUTHOR]

It is of great significance for bivalve aquaculture to promote the growth through nutritional strategy. Phosphatidic acid (PA) is a potential growth-promoting nutraceutical that targets for mammalian target of rapamycin (mTOR) in vertebrates, but its role in invertebrates remains largely unknown. Here, the effects of PA on mTOR and metabolic pathways in bivalve mollusk Sinonovacula constricta were determined by intramuscular injection with di-18 : 2 PA and di-16 : 0 PA. PA (both di-18 : 2 and di-16 : 0 PA) was found to increase the glycogen concentration in the muscle of S. constricta. Di-16 : 0 PA decreased the triglyceride concentration from 0.143 ± 0.04 mmol/g protein to 0.040 ± 0.018 mmol/g protein. The concentration of Asp, Glu, Ala, Cys, Val, Met, Ile, Leu, Phe, Arg, and Pro was reduced by di-18 : 2 PA or/and di-16 : 0 PA. PA increased the mRNA level of mTOR and the phosphorylation levels of eIF4E binding protein 1 and p70S6 kinase 1. Furthermore, PA decreased the protein level of microtubule-associated protein 1 light chain 3 Ⅱ/Ⅰ and the mRNA level of AMP-activated protein kinase. The mRNA expressions of two key enzymes of glycolysis (pyruvate kinase and glucokinase) were also upregulated by both PA, while the mRNA level of glucose transporter 1 was increased by di-18 : 2 PA. Di-16 : 0 PA decreased the mRNA level of phosphoenolpyruvate carboxykinase. The mRNA levels of sterol responsive element binding protein, fatty acid synthase, and acetyl-CoA carboxylase were increased by both PA. The mRNA level of stearoyl-CoA desaturase was increased by di-18 : 2 PA. Both PA species increased the mRNA levels of key enzymes involved in tricarboxylic acid cycle (citrate synthase and NADP-isocltrate debydrogenase). Our results indicated that PA activated mTOR signaling pathway, subsequently leading to the increase of anabolism and the inhibition of catabolism in S. constricta. [ABSTRACT FROM AUTHOR]

Isochrysis zhangjiangensis is an important microalgal species used as bait in aquaculture. However, its optimal cultivation temperature is around 25 °C, limiting its use in summer when temperature is higher. To overcome this limitation, we aimed to develop a consortia of I. zhangjiangensis and bacteria that are more resistant to heat stress. Here, six thermotolerance-promoting bacterial strains were isolated from the culture of a heat-tolerant mutant strain of I. zhangjiangensis (IM), and identified as Algoriphagus marincola, Nocardioides sp., Pseudidiomarina sp., Labrenzia alba, Nitratireductor sp., and Staphylococcus haemolyticus. Further, co-culturing I. zhangjiangensis with A. marincola under high temperature conditions increased cell density, chlorophyll a, PSII maximum photochemical efficiency (Fv/Fm), and soluble protein content of microalgae. The presence of A. marincola positively influenced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and total antioxidant capacity (T-AOC) in I. zhangjiangensis cells, while concurrently reducing the levels of reactive oxygen species (ROS). Additionally, gene expression studies confirmed that co-culturing with A. marincola upregulated the expression of antioxidant-related genes (sod and pod) and stress tolerance genes (heat shock protein genes). Our findings indicate that A. marincola effectively helps I. zhangjiangensis withstand high temperature stress, leading to improved yield of microalgae during high temperature conditions. The thermotolerance-promoting bacteria can be exploited as potential inoculants for enhancing the productivity and sustainability of bait microalgae in aquaculture. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the intestinal contents of Pacific whiteleg shrimp (Litopenaeus vannamei), the visceral mass of razor clams (Sinonovacula constricta) and the water columns and the substrate sediments in different culture-density groups in a L. vannamei–S. constricta tandem-culture model by high-throughput sequencing of the 16S rRNA gene. The results show that the culture density affected the bacterial floral structure of the water columns, substrate sediment and razor-clam gut masses without making significant differences in the bacterial flora structure of the shrimp gut; the Shannon diversity indexes of the bacterial communities in the substrate sediment, shrimp gut and razor-clam gut masses were not significantly different among the density groups, and the Shannon diversity index of the bacterial communities in the water column was higher in the group with higher culture densities; at the phylum level, the dominant bacteria common to the shrimp guts, razor-clam visceral mass, water columns and substrate sediment were Proteobacteria and Bacteroidetes; Chloroflexi was the dominant bacterium specific to the substrate sediment; and Firmicutes was the dominant bacterium specific to the shrimp gut and razor-clam gut mass. We used national standards (GB 17378.4-2007, China) to evaluate the content of water-quality factors through the environmental factors and the genus-level correlation analysis of bacterial flora that follow: the dominant bacterium in the water column, uncultured_bacterium_f_Rhodobacteraceae, was negatively correlated with PO43−-P; the dominant bacteria in the substrate sediments, uncultured_bacterium_f_Anaerolineaceae and Woeseia, were significantly and negatively correlated with DO; and the dominant bacteria Lactococcus spp. in the razor-clam gut mass and the shrimp intestines were positively correlated with DO. These results show that culture density directly affects water-quality factors, which in turn affect the culture environment and the composition structure of the bacterial flora in a cultured organism. [ABSTRACT FROM AUTHOR]

In addition to being important primary productive forces in marine ecosystems, diatoms are also rich in bioactive substances such as triacylglycerol and fucoxanthin. However, little is known about the transcriptional mechanisms underlying the biosynthesis of these substances. In this study, we found that the heat shock transcription factor PtHSF1 positively regulated the synthesis of triacylglycerol and fucoxanthin in Phaeodactylum tricornutum. Overexpression of PtHSF1 could increase the contents of triacylglycerol and fucoxanthin and upregulate key enzyme genes involved in the triacylglycerol and fucoxanthin biosynthesis pathways. On the other hand, gene silencing of PtHSF1 reduced the contents of triacylglycerol and fucoxanthin and the expression of the key enzyme genes involved in the triacylglycerol and fucoxanthin biosynthesis pathways. Further biochemical analysis revealed that PtHSF1 upregulated glycerol-2-phosphate acyltransferase 3 (GPAT3) and 1-deoxy- d -xylulose 5-phosphate synthase (DXS) by directly binding to their promoters, while genetic analysis demonstrated that PtHSF1 acted upstream of GPAT3 and DXS to regulate triacylglycerol and fucoxanthin synthesis. Therefore, in addition to elucidating the regulation mechanisms underlying PtHSF1-mediated triacylglycerol and fucoxanthin synthesis, this study also provided a candidate target for metabolic engineering of triacylglycerol and fucoxanthin in P. tricornutum. [ABSTRACT FROM AUTHOR]

For the machining process of industrial parallel robots, the gravity generated by the weight of mobile platform and links will lead to the deviation of the expected machining trajectory of the tool head. In order to evaluate this deviation and then circumvent it, it is necessary to perform the robotic stiffness model. However, the influence of gravity is seldom considered in the previous stiffness analysis. This paper presents an effective stiffness modeling method for industrial parallel robots considering the link/joint compliance, the mobile platform/link gravity, and the mass center position of each link. First, the external gravity corresponding to each component is determined by the static model under the influence of gravity and mass center position. Then, the corresponding Jacobian matrix of each component is obtained by the kinematic model. Subsequently, the compliance of each component is obtained by cantilever beam theory and FEA-based virtual experiments. In turn, the stiffness model of the whole parallel robot is determined and the Cartesian stiffness matrix of the parallel robot is calculated at several positions. Moreover, the principal stiffness distribution of the tool head in each direction over the main workspace is predicted. Finally, the validity of the stiffness model with gravity is experimentally proved by the comparison of the calculated stiffness and measured stiffness in identical conditions. [ABSTRACT FROM AUTHOR]

The mammalian target of rapamycin (mTOR) has been shown to play a central role in regulating cell growth and metabolism. However, little is known about the function of mTOR in nutrient metabolism in bivalve mollusks. In this study, the role of mTOR in the regulation of nutrient metabolism was investigated in Sinonovacula constricta. First, the activation of mTOR was assayed after starvation and refeeding. Afterwards, the role of mTOR in the regulation of nutrient metabolism was investigated using an activator (MHY1485) or inhibitor (rapamycin) of mTOR. The open reading frame of the S. constricta mTOR is 7416 bp in length and encodes a polypeptide consisting of 2471 amino acids. The mTOR amino acid sequence of S. constricta was highly conserved when compared with other species and had a close evolutionary relationship with the TOR proteins of Crassostrea gigas and Lingula anatine. mTOR was expressed in the intestine, exhalent siphon, labial palppus, muscle, inhalent siphon, gill, mantle, digestive land, and gonad tissue of S. constricta, with the highest expression in muscle. During starvation, the level of phosphorylated mTOR protein was relatively low, and the ratio of LC3II/LC3I protein and the AMPKα mRNA level significantly increased with the increase in starvation time. After feeding, the level of phosphorylated mTOR protein increased from 0.13 to 0.56, and the ratio of LC3II/I protein and AMPKα mRNA level decreased from 1.17 to 0.38. MHY1485 significantly increased the level of phosphorylated 4E-BP1 and significantly decreased the ratio of LC3II/I proteins. Furthermore, MHY1485 significantly increased the mRNA level of the glucose metabolism-related gene glucokinase (GK), significantly decreased the mRNA expression of the G6P gene, and significantly increased the mRNA expression of the lipid synthesis-related genes sterol-regulatory element-binding protein (SREBP) and stearoyl-CoA desaturase (SCD). Rapamycin significantly reduced the level of phosphorylated 4E-BP1 and the mRNA expression of mTOR, and the expression level of phosphorylated 4EBP1 decreased from 0.97 to 0.28. Meanwhile, it also significantly reduced the mRNA expression of glucose metabolism-related genes GK, pyruvate kinase (PK), glucose transporter 1 (GLUT1), and G6P, as well as lipid synthesis-related genes SCD and acetyl-CoA carboxylase (ACC). These results indicate a conserved role of mTOR in regulating nutritional metabolism, including glucose metabolism, lipid synthesis, and autophagy in S. constricta. [ABSTRACT FROM AUTHOR]

Ghrelin, glucagon-like peptide-1 (GLP-1), and peptide YY (PYY) are potent hormones mediating food intake according to the nutritional status in fish. However, limited information is available on these genes and their expression in response to nutrition in silver pomfret (Pampus argenteus). A comparison analysis revealed that ghrelin and GLP-1 were relatively conserved in marine fish. PYYa and PYYb shared a low identity and were clustered to different PYY branches. Ghrelin, pyya, and pyyb mRNAs were highly expressed in the brain, while glp-1 was highly expressed in the gills and liver. The ghrelin mRNA expression was relatively high an hour post-feeding and decreased after 3 to 72 h of fasting. The glp-1 mRNA expression was increased after 6 to 24 h of fasting. The pyya mRNA expression was increased after 72 h of fasting, while the pyyb expression remained stable during fasting. The diet with 14% lipid promoted the expressions of glp-1, pyya, and pyyb, but inhibited the ghrelin expression. The ghrelin expression in the intestine was increased after palmitic acid, oleic acid (OA), linoleic acid (LA), α-linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) incubation. OA decreased the expression of glp-1 and increased the expression of pyya. The expression of pyyb was downregulated by LA, DHA, and EPA. These results suggest the importance of ghrelin, glp-1, and pyy in coordinating food intake in response to fasting, dietary lipid concentration, and fatty acids in silver pomfret. [ABSTRACT FROM AUTHOR]

Light irradiation plays an important role in the growth of microalgae and their nutrient composition. To elucidate the effect of different LED lights (red, orange, green, blue, purple, simulated sunlight, and white) on the main nutritional compositions of Isochrysis zhanjiangensis, the growth, fatty acid composition, soluble carbohydrate, and soluble protein contents were studied. The results show that I. zhanjiangensis grew the fastest under blue light (p = 0.044). In terms of fatty acid composition, the percentage of myristic acid (C14:0) decreased significantly (p = 0.021) under blue light and simulated sunlight, but the percentages of palmitic acid (C16:0) (p = 0.032) and stearic acid (C18:0) (p = 0.037) significantly increased. The percentage of docosahexaenoic acid (C22:6n-3) increased under orange light (p = 0.021), and the percentage of total unsaturated fatty acids increased under blue light (p = 0.008). The protein content significantly increased under simulated sunlight (p = 0.025), while the carbohydrate content did not vary much (p > 0.05) under different lights. These findings provide useful guidance for optimizing the cultivation conditions of I. zhanjiangensis to improve its nutritional value and yield. [ABSTRACT FROM AUTHOR]

In recent years, the role of lectins in the feed selection of bivalve has become hot research topic. Manila clam Ruditapes philippinarum is a species of marine bivalve with important economic value. A new C-type lectin (Rpcl) from the clam was obtained and its potential role in feeding and feed selection was studied. Rpcl cDNA was 929 bp in length and had 720 bp of open reading frame. Rpcl encoded 235 amino acids, comprising a carbohydrate recognition domain (CRD) as well as an N-terminal signal peptide. Rpcl contained a conserved CRD disulfide bond including five cysteine residues (Cys125, Cys142, Cys213, Cys219, and Cys237) and the QPN motif (GLN204-PRO205-ASN206). Phylogenetic analysis revealed that the amino acid sequence of Rpcl was closely related to that of Vpclec-1 from R. philippinarum and C-type lectin from Mercenaria. The qPCR analysis indicated that Rpcl expression was observed in all examined tissues and was the highest in gills followed by in the hepatopancreas, and to a lesser extent in the mantle and lip. The in vitro agglutination experiments showed that, the purified Rpcl protein could selectively agglutinate with different microalgae. The strongest agglutinating effect with Chlorella sp. was observed, followed by Karlodinium veneficum and Chaetoceros debilis Cleve. No agglutination with Prorocentrum minimum was observed. In the feeding experiment, compared with that of the starvation group, Rpcl expression in the lip and gill of the clam fed with C. debilis and K. veneficum showed a significant upward trend with the change of time. In addition, it was found that the changes in the expression of the Rpcl gene in the gill and lip, the main feeding tissues, were consistent with the slope of the decrease in the number of algal cells in the water body. In summary, the structure of a new C-type lectin (Rpcl) was reported in this study and its correlation with the feeding and feed selection in R. philippinarum was confirmed. [ABSTRACT FROM AUTHOR]

To evaluate the pollution level and health risk of total petroleum hydrocarbon (TPH), seawater, sediments, and aquatic organisms were sampled from the southern sea area of Zhejiang Province (Yangtze River Delta, China) between 2017 and 2019. TPH was widely present in the aquatic environment and products, and its concentration was highly variable. The average value of pollution index (PI) exceeded 1 from 2017 to 2018, and 45.46–69.19% of seawater samples and 56.87–50.00% of sediment samples were polluted. The results showed significant differences in the TPH concentration in various species of aquatic organisms. The average TPH value in aquatic organisms could be ranked in the order as follows: bivalve > shrimp > crab > fish, further reflecting that the ability to accumulate and metabolize TPH existed differently among aquatic organisms within the same pond aquaculture environment. It was relatively safe to eat aquatic products since the exposure risk index was found to be far below the threshold value in this study. Therefore, it would be prudent to undertake regular monitoring of TPH to ensure effective ecosystem functioning and seafood safety in the southern Zhejiang ocean. [ABSTRACT FROM AUTHOR]

To construct an effective circular mix-culture model and investigate its culture capacity, we established one small and one large systems, with white shrimp (Litopenaeus vannamei) and razor clam (Sinonovacula constricta) cultured in separate ponds. The culture water from the L. vannamei was pumped to the S. constricta, and the culture water from the S. constricta overflowed back into the L. vannamei via gravity. In trial I, we tested four culture densities (groups 1–4), and monitored water quality, growth indices, and digestive and immune enzyme activities. From the results, the nitrogen and phosphorus levels generally increased then declined after 56 days, and were lower in groups 1 and 2. The specific growth rate of group 2 was the highest. After 56 days, activities of four digestive enzymes were increased in group 2, and lysozyme activity was significantly decreased in S. constricta in groups 1–4; Alkaline phosphatase activity of L. vannamei was increased in group 3, but decreased in S. constricta in groups 2–4; Acid phosphatase activity was significantly higher in groups 1–3 (P < 0.05), while SOD and CAT activities were significantly elevated in group 2 (P < 0.05). Thus, we applied group 2 density for trial II. In trial II, nitrogen and phosphorus concentrations declined significantly during the latter stages, and growth indices were higher than the control (P<0.05). The yields of L. vannamei and S. constricta were significantly higher than the control (P < 0.05). The results revealed a good circular mix-culture system with the optimal culture capacity for L. vannamei (40 ind m−2) and S. constricta (300 ind m−2), which provided a reference for the future culture of them. [ABSTRACT FROM AUTHOR]

Ni-Cr alloyed layers were synthesized on the surface of Q235 mild steel by double-glow plasma surface metallurgy with different electrode distance. The microstructure and phases of the alloyed layer were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD). The corrosion behavior of the Ni-Cr alloyed layers both in 3.5% NaCl and 0.5 M H2SO4 solution were systematically investigated by open-circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The obtained results reveal that the Ni-Cr alloyed layer consists of a deposited layer and an inter-diffusion layer. With increasing the electrode distance, the relative thickness, microstructure and phase composition of the Ni-Cr alloyed layers vary greatly. Polarization data show the Ni-Cr alloyed layer with the electrode distance of 15 mm has highest corrosion resistance and lowest corrosion rate, while EIS results reveal the same trend. The highest protective efficiency in 3.5% NaCl and 0.5 M H2SO4 solution are 99.23% and 99.92%, respectively, obtained for the Ni-Cr alloyed layer with 15 mm electrode distance. When the electrode distance is too large, a thin and porosity Ni-Cr alloyed layer, caused by low plasma density and Kirkendall effect, will be obtained, and will decrease the protective efficiency in corrosive medium. [ABSTRACT FROM AUTHOR]

Random matrix theory is applied in the financial field to study the correlation of the financial correlation coefficient matrix, which is a key factor in network construction. In this paper, the random matrix theory is combined with network construction to study the art financial risk prediction algorithm based on the random matrix. Based on the stochastic matrix theory and the key nodes of the network, the financial network and the "noise" network before and after the "denoising" are analyzed and compared. It is found that the key and important information of the original network is still retained after the "denoising" of the network, and the noise information corresponds to the information represented by the smaller nodes in the original network. Based on the stochastic matrix of artwork financial risk prediction, the topological properties of the financial network before and after denoising are analyzed and compared from the perspectives of minimum spanning tree, model, and community structure. Based on the random matrix theory, this paper discusses the financial correlation coefficient matrix and the statistical properties of the eigenvalues of the random matrix, and on this basis, the existing denoising methods are improved, the correlation coefficient matrix more suitable for constructing the financial network is established, and the art financial risk prediction algorithm is constructed. Then, based on the stochastic matrix theory and the key nodes of the network, the financial network and the noise network before and after denoising are analyzed and compared. It is found that the key and important information of the original network is still retained after denoising the network, and the noise information corresponds to the information represented by the relatively small nodes in the original network. Finally, based on the stochastic matrix of art financial risk prediction, analysis of the financial network topology, such as minimum spanning tree, model, and community structure, found that the improved financial network topology is more obvious and the structure is closer. [ABSTRACT FROM AUTHOR]

Marine microalga Isochrysis galbana is an important feed species with a high nutritional value. Different from other unicellular algae, its cell contains two chloroplasts which are the major sites for lipid synthesis. Here, we optimized a chloroplast isolation approach suitable for the isolation of I. galbana chloroplasts and determined the purity and integrity of the isolated chloroplasts through microscopic observations and enzyme activity assay. The chloroplast lipids were analyzed with a ultrahigh-performance liquid chromatography-Q Exactive Orbitrap-mass spectrometry. This newly developed isolation approach is simple and reliable to isolate chloroplasts with high integrity and purity. The average yield of intact chloroplasts was 15.3%±0.1%. Glycolipids and acylglycerols were the main chloroplast lipids. Glycolipids accounted for 56.6% of chloroplast lipid. Digalactosyldiacylglycerol (DGDG), monogalactosyldiacylglycerol (MGDG) and sulfoquinovosyldiacylglycerol (SQDG) were the main glyceroglycolipids. The fatty acyl R1/R2 were mostly 18:4/16:1, 18:3/16:1 and 18:4/18:5 in DGDGs, 14:0/18:4, 18:4/18:5, 18:4/18:4 and 18:3/18:4 in MGDGs and 16:0/14:0, 16:0/18:3, and 18:4/18:3 in SQDGs. In addition, diacylglycerol (DAG) was the most abundant acylglycerols; the content of 22:6/18:4-DAG was the highest. There was a little amount of glycosphingolipid (GSL) in chloroplast. Digalactosylmonoglyceride (DGMG), monogalactosylmonoglyceride (MGMG), sulfoquinovosylmonoacylglycerol (SQMG), monoglyceride (MAG), phospholipids (PLs), ceramide (Cer) and betaine lipids were nearly undetectable in chloroplast. The fatty acid proportions of DGDGs, MGDGs, SQDGs, DAGs, triglycerides (TAGs) and GSLs were either higher or lower than or similar to those of whole-cell. Collectively, our isolation approach is applicable to many aspects of chloroplast biology, and may offer a reference for the isolation of chloroplasts from other marine microalgae. [ABSTRACT FROM AUTHOR]

A healthy mental status of students plays an important role in getting quality of education. Hence, research on the prediction of college students' mental health status is of great importance and considered as a hot area of research. In this specific research study, back propagation (BP) algorithm is adopted to learn verities of characteristics of different students from the historical data of the students including: psychological characteristics, basic personal characteristics, and socio-economic characteristics. In the initial stage of the modeling, data preprocessing steps are used to prepare the data to be used by the BP algorithm for building model. The rationales behind the use of BP algorithm are its capability of handling heterogeneity of data and exploring correlations among different characteristics. The proposed model enhances the capability of BP algorithm for risk prediction of psychological problem of the students and achieves higher precision of psychological problem prediction. The results obtained show that the error between the predicted and measured values is 0.88%. [ABSTRACT FROM AUTHOR]

Peroxisome proliferator activated receptors (PPAR) are kinds of key transcriptional factors in regulating LC-PUFA biosynthesis. Until now, little is known about PPAR in marine molluscs as well as in other invertebrates. Sinonovacula constricta is the first marine mollusc that is proved to possess the complete LC-PUFA biosynthetic pathway, and it can be a perfect representative to clarify this situation. In this study, the molecular properties of S. constricta PPAR were characterized, and corresponding potential regulatory roles in S. constricta Δ6 fatty acyl desaturase (Fad) transcription were estimated by dual luciferase assay. Results showed that two PPAR homologs (PPAR_a and _b) were identified in S. constricta. They both contain typical features of vertebrate PPAR, suggesting highly conserved functional regions in PPAR. By phylogenetic comparison, they are clearly different with vertebrate PPAR and can be divided into two distinctive sub-groups. Moreover, they show a high expression level in gill, labial palps, mantle and intestine. Their down-regulated expressions in trochophore larva and veliger larva might be attributed to food-deprivation. Additionally, the transcriptional activity of S. constricta Δ6 Fad promoter was significantly activated by both PPAR_a and _b, indicating that S. constricta PPAR might play a role in the regulation of LC-PUFA biosynthesis. To our knowledge, this is the first systematic analysis of PPAR in a marine mollusc. The results will provide a valuable reference for further researches on the function of marine molluscan PPAR and their underlying mechanisms in regulating LC-PUFA biosynthesis. [ABSTRACT FROM AUTHOR]

A system of sequential extraction and purification, coupled with ultra-performance liquid chromatography coupled with quadrupole electrostatic field orbital trap high-resolution mass spectrometry (UHPLC-Q-Orbitrap-HRMS), was established and subsequently applied to the analysis of common carotenoids with very different physicochemical properties from aquatic organisms. In the first stage of extraction, free carotenoids were extracted with methanol (0.1% butylated hydroxytoluene (BHT)) and purified using hydrophile-lipophile balance column (HLB). In the second stage of extraction, extremely hydrophobic carotenoid esters were mainly extracted with methanol-dichloromethane (0.1% BHT) and purified using Alumina-N. In total, nearly 50 distinct carotenoid species were identified from common aquatic organisms by combining first-stage and second-stage solutions with recoveries of no less than 86.9%, which contained 25 free carotenoids and 24 carotenoid esters, respectively. Additionally, astacin diester 22:6/16:0, oxidized-astaxanthin diester 22:6/16:0, and adonixanthin diester 22:6/20:5 were identified for the first time from Penaeus monodon. Our results show that this methodology was a significant improvement over other alternatives for analyzing carotenoids because of its compatibility with free carotenoids and carotenoid esters and provides a technical guarantee not only for enriching carotenoid species but also for the tracing of metabolic pathways in aquatic organisms. [ABSTRACT FROM AUTHOR]

Carotenoids consist of a series of conjugated isoprene units that are characteristically highly conjugated through double bonds, leading to the formation of many isomers that are susceptible to oxidation and other chemical modifications. Extreme hydrophobicity and high complexity make carotenoids difficult to identify and quantify. We implemented the use of a common Syncronis C18 column with strong eluting solvent, here isopropanol, to successfully separate a mixture of 23 carotenoids standards with different structural properties. In addition, the method differentiated between three groups of isomeric carotenoids (lycopene/δ‐carotene/γ‐carotene/ε‐carotene/α‐carotene/β‐carotene, α‐cryptoxanthin/β‐cryptoxanthin, and zeaxanthin/lutein) by optimizing the gradient profile and using liquid chrmatography–mass spectrometry. The LOD ranged from 0.05 to 5.51 ng/mL, and the recovery of carotenoids in Mytilus coruscus was from 63.54 to 93.25%, with standard deviations <10%. Twenty‐five carotenoids were detected with a total content of 857 ± 55.1 mg/kg, and three isomeric carotenoids were identified: ε‐carotene, α‐carotene, and β‐carotene. Our results show that this methodology is a significant improvement over other alternatives for analyzing carotenoids because of its compatibility with carotenoids of different categories, and most importantly, its ability to resolve isomeric carotenes, which is significant not only for assessing carotenoid species, but also for the tracing of metabolic pathways of carotenoids. [ABSTRACT FROM AUTHOR]

The freshwater microalga Haematococcus pluvialis accumulates large amounts of fatty acids in response to adverse conditions. However, the key fatty acid desaturase genes in H. pluvialis remain unknown. In this study, we cloned and functionally characterized a A12 fatty acid desaturase gene, and designated it as HpFAD2. The open reading frame of HpFAD2 consisted of 1137 base pairs and encoded 378 amino acids. The deduced polypeptide showed 70% identity to other endoplasmic reticulum Δ12 fatty acid desaturases, whereas it had only 44% identity to plastid Δ12 fatty acid desaturases. The PSORT algorithm and phylogenetic analysis further confirmed its affiliation to the endoplasmic reticulum Δ12 fatty acid desaturases. Heterologous expression was performed in Saccharomyces cerevisiae cells transformed with the recombinant plasmid pYES2-HpFAD2. Two additional fatty acids (C16:2 and C18:2) were detected in the yeast transformants. The results indicated Δ12 desaturation activity and substrate preference for C18:1 over C16:1. The transcriptional levels of H. pluvialis HpFAD2 at different growth stages were measured by quantitative polymerase chain reaction (PCR), indicating that the HpFAD2 transcriptional levels were significantly higher in red cells than those in green cells. Our study brings more insight into the fatty acid biosynthetic pathway of H. pluvialis. [ABSTRACT FROM AUTHOR]

The large-scale farming of Nannochloropsis spp. has long been subject to high temperature. Though salicylic acid is widely used to enhance the high temperature resistance of higher plants, related research in microalgae is still in its infancy. In this study, Nannochloropsis oceanica cells at 25 °C were transferred to high temperature (35 °C) for 96 h, during which period salicylic acid with various concentrations (0, 15, 25, 35, and 50 mg L−1) were added into high temperature groups. The results indicated that high temperature could heavily inhibit the growth of N. oceanica, and result in various physiological and biochemical changes. The addition of exogenous salicylic acid at moderate concentration distinctly alleviated the inhibition of heat stress on N. oceanica. Moreover, further analysis indicated that exogenous salicylic acid could significantly increase the contents of soluble sugars, soluble proteins, total unsaturated fatty acids, and catalase activity, but result in the decrease of the nitrate reductase activity, the malondialdehyde content, and fatty acid profile. Our results also demonstrated that salicylic acid at a concentration of 15 mg L−1 received the best growth performance of N. oceanica under 35 °C. This study investigates the thermal protection effect of salicylic acid on N. oceanica under high temperature, and can provide valuable information for the large-scale production of microalgae. [ABSTRACT FROM AUTHOR]

The razor clam, Sinonovacula constricta, contains high levels of long-chain PUFA (LC-PUFA), which are critical for human health. In addition, S. constricta is the first marine mollusc demonstrated to possess Δ6 fatty acyl desaturase (Fad) and complete LC-PUFA biosynthetic ability, providing a good representative to investigate the molecular mechanism of sterol regulatory element binding proteins (SREBP) in regulating Δ6 Fad for LC-PUFA biosynthesis in marine molluscs. Herein, S. constricta SREBP and Δ6 Fad promoter were cloned and characterised. Subsequently, dual luciferase and electrophoretic mobility shift assays were conducted to explore the SREBP binding elements in the core regulatory region of S. constricta Δ6 Fad promoter. Results showed that S. constricta SREBP had a very conservative basic helix-loop-helix-leucine zipper motif, while S. constricta Δ6 Fad promoter exhibited very poor identity with teleost Fads2 promoters, indicating their differentiation during evolution. A 454 bp region harbouring a core sequence in S. constricta Δ6 Fad promoter was predicted to be essential for the transcriptional activation by SREBP. This was the first report on the regulatory mechanism of LC-PUFA biosynthesis in marine molluscs, which would facilitate optimising the LC-PUFA biosynthetic pathway of bivalves in further studies. [ABSTRACT FROM AUTHOR]

Using the case of Shanghai, this article, by starting with a discussion of the historical evolution of political legitimacy in China, analyzes the public sphere in Modern China and its native ideological origin, historical forms and functions in public opinion, and probes into its universality and particularity through a comparison with Jürgen Habermas's notion of the public sphere. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is one of the major contaminants in aquatic ecosystem. Stearoyl‐coenzyme A desaturase 1 (Scd1) has been implicated in adaptive responses to environmental stressors. The objectives of this study are (a) to characterize scd1 mRNA from silver pomfret (Pampus argenteus); (b) to investigate the expression and activity of Scd1 in silver pomfret exposed to Cd; and (c) to investigate how Cd modifies scd1 gene transcription in silver pomfret. Results indicated that Scd1 was generally conserved across fish species and scd1 mRNA level was higher by far in the brain and liver, followed by the kidney and intestine. Exposure to Cd led to significant changes of the expression and activity of Scd1 in in the liver and intestine. The liver mRNA abundance of scd1 was significantly lower in the Cd‐treated groups than in the control group. The 10 days treatment with 1 mg/L Cd significantly upregulated the intestinal scd1 mRNA level, an approximately 9‐fold higher in the 1 mg/L Cd‐treated group as compared with the control group. Accordingly, Scd1 activity indices (18:1n‐9/18:0) in the liver were significantly decreased in the 0.5 mg/L group compared with the control group, while Scd1 activity indices in the intestine were significantly increased in the 1 mg/L group compared with the control group. Moreover, overexpression of sterol regulatory element binding transcription factor 1 (Srebp1) and peroxisome proliferator–activated receptor γ (Pparγ)in HEK 293T cells produced a 2‐fold increment in the activity of the scd1 promoter. Furthermore, srebp1 had a similar expression pattern to scd1 in the liver and intestine of silver pomfret exposed to Cd. These results indicated that Cd could regulate scd1 expression, possibly through the transcriptional factor Srebp1. [ABSTRACT FROM AUTHOR]

SUMMARY: The small athecate dinoflagellate Karlodinium zhouanum is a species recently described in the coastal waters of China. K. zhouanum is morphologically similar to Karlodinium veneficum, a typical ichthyotoxic blooming karlotoxin‐producing species, and it is impossible to distinguish between these two species based on light microscopy. In this study, strains of K. zhouanum isolated from the East China Sea were studied. By analyzing toxins, toxicity, lipid characteristics and typical molecular and physiological traits of this species, K. zhouanum was shown to be nontoxic to brine shrimp and widely spread over the coastal waters of China. No karlotoxin‐like toxin was detected by liquid chromatography‐mass spectrometry (LC–MS). Instead of gymnodinosterol, the critical sterol in toxic K. veneficum, 27(nor)‐24S‐4α‐Methyl‐5α‐ergosta‐8(14)‐en‐3β‐ol (NEE) was dominant in K. zhouanum, while gymnodinosterol was absent. These sterol characteristics may provide not only support for the species separation between toxic and nontoxic species of Karlodinium but also environmental survey tools to differentiate the contribution of nontoxic Karlodinium strains, which has been unclear until now. [ABSTRACT FROM AUTHOR]

Bivalves, a highly diverse and the most evolutionarily successful class of invertebrates native to aquatic habitats, provide valuable molecular resources for understanding the evolutionary adaptation and aquatic ecology. Here, we reported a high‐quality chromosome‐level genome assembly of the razor clam Sinonovacula constricta using Pacific Bioscience single‐molecule real‐time sequencing, Illumina paired‐end sequencing, 10X Genomics linked‐reads and Hi‐C reads. The genome size was 1,220.85 Mb, containing scaffold N50 of 65.93 Mb and contig N50 of 976.94 Kb. A total of 899 complete (91.92%) and seven partial (0.72%) matches of the 978 metazoa Benchmarking Universal Single‐Copy Orthologs were determined in this genome assembly. And Hi‐C scaffolding of the genome resulted in 19 pseudochromosomes. A total of 28,594 protein‐coding genes were predicted in the S. constricta genome, of which 25,413 genes (88.88%) were functionally annotated. In addition, 39.79% of the assembled genome was composed of repetitive sequences, and 4,372 noncoding RNAs were identified. The enrichment analyses of the significantly expanded and contracted genes suggested an evolutionary adaptation of S. constricta to highly stressful living environments. In summary, the genomic resources generated in this work not only provide a valuable reference genome for investigating the molecular mechanisms of S. constricta biological functions and evolutionary adaptation, but also facilitate its genetic improvement and disease treatment. Meanwhile, the obtained genome greatly improves our understanding of the genetics of molluscs and their comparative evolution. [ABSTRACT FROM AUTHOR]

Background: Sinonovacula constricta is an economically important bivalve species in China, Korea and Japan that widely resides in estuarine and coastal areas where salinity fluctuates rapidly. However, little is known about its adaptation mechanisms to acute salt stresses. Objective: To reveal the underlying molecular mechanisms involved in acute salt stresses in juvenile S. constricta. Methods: Nine cDNA libraries (triplicate each trial) were established from juvenile S. constricta, which were subjected to low salinity (5 psu), optimal salinity (15 psu) and high salinity (25 psu) for 6 h, respectively. Results: Illumina sequencing generated 478,587,310 clean reads totally, which were assembled into 427,057 transcripts of 246,672 unigenes. Compared with the control, 1259 and 2163 differentially expressed genes (DEGs) were identified under acute low and high salt stresses, respectively. GO and KEGG enrichment analyses of DEGs revealed that several key metabolic modulations were mainly responsible for the acute salt stresses. According to the significantly highlighted KEGG pathways, some key DEGs were identified and discussed in details. Notably, based on which, some potential osmolytes were further speculated. Conclusion: Here, we carried out a unique report of comparative transcriptome analyses in juvenile S. constricta in response to acute salt stresses. The identified DEGs and their significantly enriched GO terms and KEGG pathways were critical for understanding and further investigating the underlying the physical and biochemical performances, and ultimately facilitated S. constricta breeding. Besides, the transcriptome data greatly enriched the genetic information of S. constricta, which were valuable for promoting its molecular biology researches. [ABSTRACT FROM AUTHOR]

This study investigated the expression of zebrafish (Danio rerio) fatty acid transporters, such as scavenger receptor CD36, plasma membrane fatty acid‐binding protein (FABPpm), and fatty acid transport protein family (FATPs), in responses to nutritional status and diet composition. For diet composition study, three isonitrogenous (43% crude protein) purified diets were formulated to contain 6%, 12% and 18% crude lipid levels. Meanwhile five isonitrogenous and isoenergetic purified diets were formulated to contain different lipid sources including fish oil (FO; rich in n‐3 HUFA), palmitic acid (PA; rich in C16:0), olive oil (OO; rich in C18:1n‐9), sunflower oil (SO; rich in C18:2n‐6) or perilla oil (PO; rich in C18:3n‐3) as the sole lipid source. Results showed that liver CD36, FABPpm‐a, FABPpm‐b, FATP1‐a and FATP6, intestine CD36, FABPpm‐a and FABPpm‐b, and muscle CD36 and FATP1‐b were significantly increased during postprandial period. During starvation, liver CD36, FABPpm‐a, FABPpm‐b and FATP1‐a, intestine FABPpm‐a, FABPpm‐b, FATP4 and FATP6, and muscle FATP1‐b, FATP4 and FATP6 were significantly increased. The expression of some fatty acid transporters (including liver CD36 and FABPpm‐b, intestine FABPpm‐a, and muscle CD36, FABPpm‐a, FATP1‐a, FATP2 and FATP4) was up‐regulated by refeeding, while the expression of other fatty acid transporters (liver FABPpm‐a and intestine FATP1‐a, FATP4 and FATP6) was down‐regulated by refeeding. The expression of several fatty acid transporters (liver FATP2 and FATP4, and intestine CD36, FATP2 and FATP4) was significantly increased by high‐lipid diet, whereas CD36, FATP1‐b, FATP2 and FATP4 expression in the muscle were reduced by increasing dietary lipid level. Compared with FO group, the muscle of fish fed the diet with OO had a higher CD36 mRNA abundance, while the muscle of fish fed the diet with OO and PO had a higher FATP1‐b expression. Compared with the FO group, the hepatic FATP2 mRNA was significantly increased in the PA group, while the intestine FATP2 mRNA was significantly increased in the SO and PO groups. In addition, intestine FATP4 expression in the PA and OO groups was lower compared with the FO group. The results indicate that zebrafish fatty acid transporters play a central role in coordinating the mobilization of fuel substrates in responses to nutritional status and diet composition. [ABSTRACT FROM AUTHOR]

This article discusses the continuity of the May Fourth discourse in the last thirty years. Although much has changed in China economically and socially, many fundamental problems of the country remain unresolved. Therefore, the May Fourth discourse of today continues to raise the same questions as before. [ABSTRACT FROM AUTHOR]

Volatiles with a pleasant smell are typical characteristics of both raw and cooked seafood. However, the effect of salinity on volatiles in marine bivalves remains unclear. In the current study, the volatiles in raw and cooked Sinonovacula constricta cultured under different salinities were investigated by head space-solid phase microextraction and gas chromatography-mass spectrometry. Overall 28 volatiles were identified in the raw samples and mainly comprised 1-pentanol (15.32-23.95%), 1,5-octadien-3-ol (14.20-16.73%) and 1-octen-3-ol (14.20-15.63%). A total of 41 volatiles, dominated by pentanal (32.33-46.80%), 1-pentanol (10.88-16.48%) and hexanal (5.64-13.70%), were determined in the cooked samples. Irrespective of whether they were raw or had been cooked, S. constricta cultured under high salinity possessed more abundant volatiles than those reared under low salinity. When the culture salinity of S. constricta was raised, changes in the volatile content occurred. For S. constricta cultured at low salinity, rearing at high salinity for several days prior to harvest could greatly improve the volatile content. This finding is of value for the improvement of volatiles important for odor and taste in other marine bivalves. [ABSTRACT FROM AUTHOR]

Much attention has been paid on studies of astaxanthin accumulation process in Haematococcus pluvialis industry. However, growth of H. pluvialis in motile vegetative stage is still the most important and problematic part in the whole cultivation process, such as low growth rate and cell yields. Motile vegetative cells are extremely sensitive to various stresses which make it difficult to maintain the cells of this state to grow. Previous reports showed that motile vegetative cells may have higher biomass yields if applied monochromatic red light. However, metabolic responses of these cells are not completely understood, which constraints application of this illumination protocol in industry. The aim of this study was to examine how critical biochemical changes of H. pluvialis motile vegetative cells were affected by red light when compared with white light. Variation of photosynthetic pigments composition and lipids were mainly studied. By comparing growth process of cultures in red light and white light, prominent variation of pigments composition and lipids changes were observed. The results showed that, even though cell proliferation was the same during exponential growth phase, variation of photosynthetic pigment composition and lipids occurred. The final biomass of cell number was higher in red light group than in white light group. The variations were significant different. Increase or decrease of major photosynthetic membrane lipids to some extent did not influence photosynthesis of the vegetative cells during this phase. However, vegetative cells under polychromatic white light other than monochromatic red light need further metabolic process to adjust its pigment composition and lipids, possibly this is energetically and biochemically unfavorable for motile vegetative cells to growth under white light, a light condition normally not considered as a stress. [ABSTRACT FROM AUTHOR]

Salmonella is a major pathogen that causes acute foodborne outbreaks worldwide. Seafood, particularly shellfish, is a proven source of Salmonella spp. infection because many people prefer to eat it raw or lightly cooked. However, traditional identification methods are too time-consuming and complex to detect contamination of bacteria in the food chain in a timely manner, and few studies have aimed to identify Salmonella in shellfish early in the supply chain. We herein developed a method for rapid detection of Salmonella in shellfish based on the method of recombinase polymerase amplification (RPA) combined with lateral flow dipstick (LFD), which targets the invasion gene A (invA). The RPA-LFD was able to function at 30-45 °C, and at the temperature of 40 °C, it only took 8 min of amplification to reach the test threshold of amplicons. The established method had both a good specificity and a sensitivity of 100 fg DNA per reaction (20 µL). Regarding practical performance, RPA-LFD performed better than real-time PCR. Another advantage of RPA-LFD is that it was capable of being performed without expensive equipments. Thus, RPA-LFD has potential for further development as a detection kit for Salmonella in shellfish and other foods under field conditions. [ABSTRACT FROM AUTHOR]

SUMMARY: Lipid metabolites play an important role in understanding the stress physiology of Pyropia haitanensis, and can be used to facilitate development of stress‐resistant Pyropia cultivars. Therefore, in this study ultra performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC‐Q‐TOF‐MS) and gas chromatography–mass spectrometry (GC–MS) based metabolomics approaches were developed to screen the responses of lipid metabolites such as phospholipids, glycolipids, fatty acids and volatile organic compounds (VOCs) to different heat shock times. A total of 26 potential lipid biomarkers including Lyso‐monogalactosyldiacylglycerol (Lyso‐MGDG), Lyso‐digalactosyldiacylglycerol (Lyso‐DGDG), sulfoquinovosylmonoacylglycerols (SQMG), sulfoquinovosyldiacylglycerol (SQDG), diacylglyceryltrimethylhomoserine (DGTS), triacylglycerol (TAG), Lyso‐phosphatidicacid (Lyso‐PA), Lyso‐phosphatidylcholine (Lyso‐PC), Lyso‐phosphatidylethanolamine (Lyso‐PE), Lyso‐phosphatidylglycerol (Lyso‐PG), phosphatidylglycerol (PG), phosphatidylinositol (PI), and phosphatidylinositol phosphate (PIP) were identified, most of which responded to high temperature by reducing or increasing levels after stimulation for 1 h or 6 h. After times longer than 6 h, the levels of most lipids gradually recovered to the control group levels. Moreover, the balance of lipids and fatty acids transformation was disrupted. Overall, 11 total fatty acids (TFAs), 13 free fatty acids (FFAs) and 29 VOCs were identified during 0–72 h of high temperature stress. The FFAs, especially polyunsaturated C 20 fatty acids and VOCs, showed opposing change trends, indicating the transformation between C 20 fatty acids and VOCs. Overall, this study provides important insights into the metabolic variations of P. haitanensis under different heat shock time and the relationship between the conversion of lipids, fatty acids, and VOCs. The information provided herein will facilitate efficient development and improvement of Pyropia quality by producing cultivars resistant to high temperature. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Steryl glycosides (SGs) are sterol conjugates found in various plants, especially in those making up human diets. It has been demonstrated that SGs have potential health benefits, and they could be used as food supplements in a variety of food matrixes. Marine microalgae are a potential resource for human food and ingredients. In this study, gas chromatography–triple quadrupole mass spectrometry (GC–QQQ‐MS) was used to characterize unknown SGs in eight microalgae belonging to different classes (Isochrysis galbana 3011, Pavlova viridis, Platymonas helgolandica, Conticribra weissflogii, Thalassiosira pseudonana, Nitzschia closterium, Gymnodinium sp., and Karlodinum veneficum). RESULTS: The SGs were first extracted from lyophilized algae with chloroform–methanol, purified by solid‐phase extraction and analyzed as trimethylsilyl derivatives. Nine SGs have been identified. In particular, new SGs like occelasteryl glycoside and stellasteryl glycoside were found in Gymnodinium sp., 24‐methylene cholesteryl glycoside was detected in P. helgolandica, and 4,24‐dimethylcholestan‐3‐yl glycoside was identified as the main constituent of microalga K. veneficum. The results also showed that the compositions of SGs in different microalgae varied, with a range of 5.234 to 0.036 g kg−1, and microalga P. viridis contained the most abundant SGs. CONCLUSION: GC–QQQ‐MS is a powerful tool to detect SGs with different structures from a variety of microalgae. The compositions of SGs in different microalgae varied greatly. Microalgae are a good source of highly valued SGs. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Sinonovacula constricta is an economically and nutritionally important bivalve native to the estuaries and mudflats of China, Japan and Korea. In the present study, S. constricta, cultured either under experimental conditions or collected directly from natural coastal areas with different seawater salinities, was investigated for changes in proximates, amino acids and lipids. RESULTS When culture salinity was increased, levels of moisture, carbohydrate, crude protein and crude lipid were significantly decreased, whereas the level of ash was significantly increased. The level of Ala was increased by 1.5- to 2-fold, whereas the contents of most lipids were significantly decreased, and the proportion of phosphatidylethanolamine was significantly increased. Notably, a high proportion of ceramide aminoethylphosphonates was detected in S. constricta reared at all salinities. The energy content appears to be higher in S. constricta reared at higher salinity. In experimental S. constricta, when the salinity was enhanced, the changes of compositions were very close to those reared at constant high salinity. CONCLUSION Sinonovacula constricta reared at higher salinities possesses a superior quality. A short period of exposure to a higher salinity for farmed S. constricta reared at a lower salinity before harvest would be useful with respect to improving its nutritive value. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

To investigate the effects of short-term starvation on lipid metabolism, juvenile silver pomfret ( Pampus argenteus) with an initial weight of 18.1 ± 1.53 g were starved for 6 days. Fish were sampled on days 0, 2, 4 and 6 of starvation (S0, S2, S4 and S6, respectively) and then analysed. The results showed that short-term starvation induced a significant decrease in visceral index, hepatosomatic index. The crude lipid content was also significantly decreased by 42.22% and 82.96% on S2 and S6 respectively. In addition, short-term starvation significantly decreased the plasma triacylglycerol, non-esterified fatty acid and low-density lipoprotein cholesterol. Moreover, short-term starvation significantly increased the expressions of hormone-sensitive lipase ( HSL) and adipose triglyceride lipase ( ATGL) at the mRNA and protein levels in the muscle and the ATGL expression at the protein level in the liver. The expressions of fatty acid translocase ( CD36) and plasma membrane fatty acid-binding protein ( FABPpm) at the protein level in the muscle were significantly increased by short-term starvation, while the expressions of fatty acid transport protein 1 ( FATP1), FABPpm and lipoprotein lipase ( LPL) at the protein level in the liver were significantly increased by short-term starvation. Furthermore, the expressions of peroxisome proliferator activated receptor ( PPAR) α and PPARγ at the mRNA and protein levels in the muscle were significantly elevated by short-term starvation. These findings suggested that short-term starvation increased lipid mobilization and utilization possibly through activation of lipolysis-related genes ( HSL and ATGL), lipid uptake-related genes ( LPL, CD36, FATP1 and FABPpm) and PPARs. [ABSTRACT FROM AUTHOR]

Characterization of the feeding preferences of bivalve larvae would help improving the bivalve aquaculture and hatchery by providing appropriate microalgal diets. However, inaccurate and laborious identification and counting of microalgal species have challenged the selective feeding of bivalves. In the present study, we developed a highly specific and sensitive assay using quantitative polymerase chain reaction (qPCR) to assess the selective feeding of bivalve larvae based on species-specific primers targeting to microalgal 18S rDNA sequences. The assay exhibited good specificity. The detection limits of the qPCR assay were 769, 71, 781 and 21 18S rDNA copies for Chaetoceros calcitrans, Isochrysis galbana, Platymonas helgolandica and Nannochloropsis oculata, respectively. Using such assay, we found that C. calcitrans and I. galbana were preferentially ingested, whereas N. oculata was preferentially rejected in biodeposits of four bivalve species, Tegillarca gransa, Cyclina sinensis, Scapharca subcrenata and Sinonovacula constricta. Furthermore, our growth experiments revealed that C. calcitrans and I. galbana could significantly promote the shell growth, whereas feeding of N. oculata resulted in poorer growth of four bivalve species. These data indicated that qPCR might be useful in screening of efficient and reliable microalgal species for each bivalve species, leading to improved bivalve aquaculture and hatchery. [ABSTRACT FROM AUTHOR]

Rationale Diacylgycerol- N-trimethylhomoserine (DGTS) and diacylglycerylhydroxymethyl- N,N,N-trimethyl-β-alanine (DGTA) are structural isomers that are the most commonly described betaine lipids in microalgae. The structural differentiation and precise identification of DGTS and DGTA in microalgae need to be established during mass spectrometry analysis. Methods Total lipid was extracted from Amphora spp. with CHCl3/CH3OH (1:1, v/v). The qualitative analysis of DGTS and DGTA in Amphora spp. was carried out using Li+/H+ dual mode by ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry operating in MSE mode (UPLC/QTOF MSE). Results Characteristic fragment ions [C10H22O5N]+ at m/z 236.15 and [C7H14O2N]+ at m/z 144.10 from the [M + H]+ precursor ion can be used for the qualitative analysis of both DGTA and DGTS, whereas the loss of m/z 87 and 74 from the [M + Li]+ precursor ion are specific for DGTS, and the loss of m/z 103 from the [M + Li]+ precursor ion is only for DGTA. As a result, 9 DGTSs and 16 DGTAs with different fatty acids were identified simultaneously in Amphora spp. Semi-quantitative analysis of DGTS and DGTA in Amphora spp. showed that the contents of DGTS ranged from 0.003 to 0.438 nmol mg-1 dw, and that of DGTA from 0.004 to 0.414 nmol mg-1 dw. Conclusions This is the first report to achieve the ambiguous structural identification of DGTS and DGTA by UPLC/QTOF MSE using dual Li+/H+ adduct ion mode, which has remained a challenge in the past. It could provide new insights into their phylogeny and be helpful to characterize the natural phytoplankton communities as intact polar lipid biomarkers. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Isochrysis galbana is a species of marine microalgae that is principally used to feed the larvae and early juveniles of bivalve mollusks (e.g., ark shells, clams, mussels, oysters and scallops). The artificial hatchery stages of most of these larvae are primarily occur during high-temperature seasons, when the water temperature in the breeding pool frequently exceeds 30 °C and even reaches 35 °C, which may change the lipid composition of I. galbana, thus affecting its nutritional value. In this experiment, we investigated changes in the lipid composition of I. galbana Parke at high temperature using ultra-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry. The results showed that the sulfoquinovosyldiacylglycerol (SQDG), monogalactosyldiacylglycerol (MGDG), diacylglycerylcarboxyhydroxymethylcholine (DGCC) and digalactosyldiacylglycerol (DGDG) contents increased during growth at 20 and 35 °C. Conversely, the lyso-SQDG, lyso-MGDG, lyso-DGDG, lyso-DGCC and triacylglycerol (TAG) contents clearly decreased. Moreover, higher SQDG, MGDG, DGDG and DGCC contents and lower lyso-lipid and TAG contents were observed in I. galbana Parke grown at 35 versus 20 °C. In addition, the content of docosahexaenoic acid (DHA) improved at 20 and 35 °C during growth, and DHA accumulated to greater levels at 35 °C than at 20 °C at the same time points. These results revealed an increase in DHA content as the temperature rose, which indicated that the nutritional value of I. galbana Parke during logarithmic phase improved in the same cultured time with an increasing temperature. [ABSTRACT FROM AUTHOR]

BACKGROUND Head space solid-phase microextraction-gas chromatography-mass spectrometry has been applied to analyze the volatile components of six marine microalgae ( Thalassiosira weissflogii, Nitzschia closterium, Chaetoceros calcitrans, Platymonas helgolandica, Nannochloropsis spp . and Dicrateria inornata) from Bacillariophyta, Chlorophyta and Chrysophyta, respectively, in different growth phases. RESULTS All volatile compounds were identified by database searching in the NIST08 Mass Spectral Library and analyzed by principal component analysis with SIMCA-P software (Umetrics, Umea, Sweden). The results clearly revealed that the volatile components of the six microalgae were significantly different in the exponential, stationary and declining phases. Aldehydes, alkanes, some esters and dimethyl sulfide significantly changed in different growth phases. CONCLUSION This is the first report on the comprehensive characteristics of volatile components in different microalgae and in different growth phases. The results may provide reference data for studies on the flavor of cultivated aquatic organism, odor formation in nature water, choice of feeding period and microalgae species selection for the artificial rearing of marine organisms. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]