Search Results (40)

Cadmium (Cd) is a typical pollutant with strong toxicity even at low concentrations. In the marine environment, Cd is a problem of magnitude and ecological significance due to its high toxicity and accumulation in living organisms. The clam Meretrix meretrix is a useful bioindicator species for evaluating heavy-metal stress. This study investigated the extent of recovery from Cd²⁺-induced oxidative and immune impairments in M. meretrix gills achieved by short-term depuration. Clams were exposed to 3 mg/L Cd²⁺ for six days or three days followed by three days of depuration, and the Cd contents, morphological structure, osmoregulation, oxidative stress, and immune responses in the gills were evaluated. The results showed that gill Cd contents increased with exposure, reaching 9.857 ± 0.074 mg·kg⁻¹ on day 3 but decreased slightly to 8.294 ± 0.056 mg·kg⁻¹ after depuration, while reaching 18.665 ± 0.040 mg·kg⁻¹ on day 6 after continuous exposure. Histological lesions, including lamellar fusion, hemolymphatic sinus dilation, and ciliary degeneration, partially recovered after depuration. Reactive oxygen species (ROS) and malondialdehyde (MDA) levels decreased significantly, while DNA-protein crosslinking rate (DPC) and protein carbonyl (PCO) showed minor reductions. Total antioxidant capacity (T-AOC) and the activities of Ca²⁺/Mg²⁺-ATPase (CMA), cytochrome c oxidase (COX), succinate dehydrogenase (SDH), and lactate dehydrogenase (LDH) increased by over 10% during depuration, though these changes were not statistically significant. Lysozyme (LZM) activity and MT transcript levels increased progressively with Cd exposure, indicating their suitability as biomarkers of Cd stress. Acid and alkaline phosphatase (ACP, AKP) activities and Hsp70 and Nrf2 mRNA transcripts exhibited inverted U-shaped response consistent with hormetic response. ACP and AKP activity levels rose by more than 20% after depuration, suggesting partial restoration of immune capacity. Overall, Cd exposure induced oxidative damage, metabolic disruption, and immune suppression in M. meretrix gills, yet short-term depuration allowed partial recovery. These findings enhance understanding of Cd toxicity and reversibility in marine bivalves and reinforce the usage of biochemical and molecular markers for monitoring Cd contamination and assessing depuration efficiency in aquaculture environments. Full article

The clam Meretrix meretrix (Linnaeus, 1758) is a commercially significant bivalve species widely distributed along China’s coast. To investigate the differences among geoducks from different geographic populations, this study investigated the geographical variations in morphology and key physiological traits among three populations spanning a latitudinal gradient: Liaoning Dandong (north), Jiangsu Rudong (center), and Guangxi Qinzhou (south). We analyzed nine morphological traits and measured physiological indicators—including filtration rate, feeding rate, oxygen consumption, ammonia excretion, and burrowing behavior—at two temperatures (18 °C and 20 °C). The results revealed significant morphological differentiation among the populations. Physiologically, the Guangxi population demonstrated superior adaptation to warmer conditions, exhibiting the highest feeding and metabolic rates at 20 °C. In contrast, the Liaoning population performed better at the lower temperature of 18 °C, while the Jiangsu population showed intermediate characteristics. Furthermore, burrowing capacity varied significantly, with the southern population having the highest burrowing rate. These findings demonstrate clear population-specific adaptations to local thermal environments, likely driven by long-term acclimatization. This study provides a crucial scientific basis for the conservation of genetic resources and informs regionalized aquaculture strategies for M. meretrix, emphasizing the importance of selecting locally adapted populations for cultivation. Full article

Flavor quality fundamentally influences the market value of bivalves, yet the molecular basis of interspecific umami variation remains poorly understood, hindering flavor-directed breeding. This study compared umami compounds and related gene expression across six economically important bivalve species from Southeast China: Crassostrea sikamea, Meretrix meretrix, M. mercenaria, Cyclina sinensis, Ruditapes philippinarum, and Sinonovacula constricta. Using quantitative chemical analysis and qPCR, key taste components and gene expression levels were assessed during the peak flavor season. Results identified glutamic acid, aspartic acid, guanosine monophosphate, and adenosine monophosphate as major umami contributors. Crassostrea sikamea showed the highest umami intensity (Equivalent umami concentration = 449.35 g Monosodium Glutamate/100 g dry weight), followed by Meretrix meretrix (EUC = 329.56 g MSG/100 g dry weight). Expression of glutamate dehydrogenase 1 strongly correlated with glutamic acid content (r = 0.90, p < 0.01), indicating its regulatory role. glutamic-oxaloacetic transaminase 1 and adenylosuccinate synthase also associated positively with aspartic and glutamic acids, respectively, while hypoxanthine phosphoribosyltransferase 1 correlated negatively. Bioinformatics revealed species-specific variations in key enzyme active sites. This study integrates flavor phenotyping with genetic analysis, offering novel insights into umami regulation and providing candidate genes for molecular breeding aimed at flavor enhancement, but subject to further functional validation and heritability analysis. Full article

This study employed a multi-technique approach to investigate the structural and conformational changes in proteins in Meretrix lyrata (M. lyrata) adductor, foot, and siphon tissues during boiling. Data-independent acquisition (DIA) quantitative proteomics was utilized to identify differentially expressed proteins (DEPs) in six temporal comparison groups (20–0 s, 40–20 s, 60–40 s, 80–60 s, 100–80 s, and 120–100 s). The results showed that key myofibrillar proteins, including myosin heavy chain, paramyosin, and actin, exhibited tissue-specific expression patterns, while low-molecular-weight degradation fragments (<17 kDa) appeared with prolonged heating. Turbidity measurements peaked in adductor and siphon tissues at 60 s and in foot tissue at 80 s. Heating resulted in a narrowed particle size distribution (100–1000 nm), and a decreased zeta potential, indicating a reduction in protein surface charge. Fourier transform infrared spectroscopy revealed hydrogen bond disruption and secondary structure transitions, marked by a reduction in α-helix content with a corresponding increase in β-sheet and random coil structures. In total, 6527 proteins were identified, and Gene Ontology (GO) enrichment analysis highlighted the DEPs’ involvement in biological regulation and metabolic processes. Collectively, these results provide comprehensive characterization of protein denaturation, degradation, and structural reorganization in M. lyrata tissues during the boiling process. Full article

This study examined the sediment microbial communities at 12 stations within the Meretrix meretrix farming area in Rudong, Jiangsu Province, utilising high-throughput sequencing. It elucidates the ecological relationships between the sediment microbial communities and the primary physical and chemical factors influencing the farming water and sediment. The results indicated that the microbial communities comprised 55 phyla. The Shannon index ranged from a minimum of 8.97 to a maximum of 9.96, while the Simpson index varied from 0.996 to 0.997, indicating a uniform species distribution. β diversity analysis revealed significant spatial diversity among the communities. Dominant bacterial groups included Proteobacteria (25.2–38%) and Desulfobacterota (10.4–14.4%), with Desulfobacterota reaching a peak of 14.4% at tidal creek station S2, reflecting the sulphate reduction process associated with organic pollution input. At the genus level, Woesia (9.15–17.16%), Desulfobacterota, and Subgroup_22 were identified as core functional bacteria. Redundancy analysis indicated that phosphate and nitrate were the primary drivers of community variation, accounting for a cumulative interpretation rate of 43.2%. Spearman correlation analysis confirmed that fine-grained sediments were more likely to store organic matter, significantly promoting the colonisation of AQS1 (p < 0.05) and Cohaesibacter (p < 0.05), while inhibiting Puniceispirillales (p < 0.01). An alkaline environment positively selects for sulphur-cycling bacteria, such as Desulfatiglans (p < 0.05). This study provides technical support for the regulation of sediment environments and the promotion of healthy clam culture practices. Full article

(1) Exploring the potential impacts of Mactra veneriformis and Ruditapes philippinarum on the aquaculture of Meretrix meretrix in the tidal flat aquaculture zone is significant for the optimization of bivalve aquaculture structure. (2) In this study, we systematically compared the differences in feeding, metabolic physiological indicators, and energy budgets of the three bivalve species in the M. meretrix aquaculture zone of Rudong County, Jiangsu Province, under the feeding conditions of Isochrysis zhanjiangensis and Platymonas helgolandica. (3) The results indicated that feeding with I. zhanjiangensis could significantly improve the feeding efficiency of the three bivalve species, and M. veneriformis showed the strongest feeding ability. Under I. zhanjiangensis feeding conditions, the clearance rate [1.373 ± 0.177 L/(g·h)] and ingestion rate [9.803 ± 1.264 mg/(g·h)] of M. veneriformis were significantly higher than those of M. meretrix [clearance rate: 0.716 ± 0.046 L/(g·h); ingestion rate: 5.112 ± 0.328 mg/(g·h)] and R. philippinarum [clearance rate: 0.609 ± 0.101 L/(g·h); ingestion rate: 4.351 ± 0.725 mg/(g·h)] (p < 0.05). In terms of energy allocation, the scope for growth (SFG) of M. veneriformis [133.050 ± 15.705 J/(g·h)] was significantly higher than that of the other two bivalve species. M. meretrix [70.550 ± 2.133 J/(g·h)] had the highest energy utilization efficiency, while R. philippinarum [53.688 ± 7.548 J/(g·h)] had the lowest SFG due to high excretion losses. (4) In conclusion, M. veneriformis shows high production potential in the aquaculture system, and its potential impact on M. meretrix is greater than that of R. philippinarum, thus requiring close attention in aquaculture management. Full article

In this study, nanoparticles prepared by the heat-induced self-assembly of bovine serum albumin-dextran conjugates (BSA-DX) were utilized as an effective delivery system for the immunoregulatory peptide Gln-Leu-Asn-Trp-Asp (QLNWD) from Meretrix meretrix. The effects of dry-heating duration on the fabrication and characteristics of glycoprotein nanoparticles (GBA NPs) were investigated. Stable GBA NPs (110.84 nm) were obtained after 9 h of dry-heating. Depending on the addition sequence of QLNWD, the QLNWD-loaded nanoparticles were categorized into two types: pre-loading and post-loading. The two strategies were evaluated based on physicochemical characterization, colloidal stability, and RAW264.7 macrophage uptake. Results showed that upon QLNWD incorporation, both pre-loading NPs and post-loading NPs exhibited spherical morphology, with particle sizes decreasing to 105.51 nm and 94.27 nm, respectively. The encapsulation efficiency of pre-loading NPs for QLNWD was higher (87.74%), and the co-localization ability between post-loading NPs and QLNWD was stronger (Pearson’s correlation coefficient = 0.95). In vitro simulated gastrointestinal digestion experiments showed that QLNWD bioaccessibility increased to 47.5% and 42.7% for pre-loaded and post-loaded NPs, respectively. Compared to free QLNWD, NP encapsulation significantly enhanced the uptake of QLNWD by macrophages. Thus, GBA NPs, particularly those prepared by the pre-loading method, are considered promising delivery systems for marine bioactive peptides. Full article

Clam farms are typically located in remote areas with limited computational resources, making it challenging to deploy traditional deep learning-based object detection methods due to their large model size and high computational demands. To address this issue, this paper proposes a lightweight detection method, YOLOv8-RFD, based on an improved YOLOv8 algorithm, tailored for clam sorting applications. The proposed enhancements include the following: replacing the original backbone network of YOLOv8 with a Reversible Columnar Network (RevColNet) to reduce feature redundancy and computational load; upgrading the C2f modules in both the backbone and neck networks to C2f-Faster to optimize feature fusion strategies and improve fusion efficiency; and incorporating a Dynamic Head (DyHead) to enhance feature extraction and detection accuracy by adaptively adjusting the detection head structure. Experimental results on a custom clam dataset demonstrate that, compared to the original YOLOv8 model, the proposed method reduces the number of parameters by 22.75% and computational demand by 18.52%, while slightly improving detection accuracy. These improvements not only maintain but also enhance detection performance, significantly reducing computational cost, and confirming the method’s suitability for deployment in resource-constrained environments. This provides a reliable technical foundation for the sorting of clams. Full article

Coastal wetlands are critical components of blue carbon ecosystems, yet the functional roles of benthic shellfish species in regulating sediment carbon dynamics are not yet fully elucidated. To address this knowledge gap, we investigated the effects of different shellfish zones—gastropods (Bullacta exarata, Umbonium thomasi) and bivalves (Mactra veneriformis, Meretrix meretrix, Potamocorbula laevis)—on sediment carbon fractions and microbial communities in representative intertidal wetlands of Liaodong Bay, China. We analyzed dissolved organic carbon (DOC), particulate organic carbon (POC), microbial biomass carbon (MBC), enzyme activities, and microbial genomic profiles, with particular emphasis on carbon fixation gene abundance within the top 0–10 cm of sediment. The results showed that POC and MBC levels in gastropod zones were 56.11% and 99.83% higher, respectively, than in bivalve zones, while carbon fixation gene abundance was 14.54% lower. Structural equation modeling (SEM) further revealed that shellfish type had a significant direct effect on MBC (λ = 0.824, p < 0.001). This study provides novel evidence that shellfish community composition regulates blue carbon storage through both biogeochemical and microbial pathways, highlighting the importance of species-specific management in shellfish aquaculture to enhance carbon sequestration. These findings offer a theoretical foundation for future assessments of coastal wetland carbon sinks and ecosystem service valuation. Full article

This study aimed to systematically investigate and compare the biochemical composition of 13 locally abundant shellfish species (Dalian, China) and the taste characteristics of these shellfish and their boiling liquids. The results showed that Chlamys farreri exhibited the highest level of protein (64.58%) and polyunsaturated fatty acids (53.84% of total fatty acids), whereas Scapharca subcrenata showed a better composition and proportion of essential amino acids (EAA/TAA = 39.02%, EAA/NEAA = 63.98%) compared to other species. Glu, Gly, Ala, Arg, 5′-monophosphate (GMP), lactic acid, succinic acid, and malic acid were quantitatively determined as the main taste compounds in shellfish and their boiling liquids. The equivalent umami concentration (EUC) values, reflecting the synergistic effect of umami compounds, showed distinct characteristics, and the maximum umami intensities were found in Meretrix meretrix (586.8 g monosodium glutamate (MSG)/100 g) and the boiling liquid of Clinocardium californiense (358.3 g MSG/100 g), respectively. Based on these experimental results, C. californiense was found to have the highest prehensive quality score as revealed by principal component analysis (PCA). These results are important for promoting studies aimed at nutritional value development and taste compounds improvement of these shellfish species, especially for flavor enhancer development. Meanwhile, different shellfish species can be comprehensively developed and utilized based on their distinct nutritional properties, and this would translate into greater profitability for producers. Full article

Our previous genome analysis of Sinonovacula constricta revealed an expansion of the monocarboxylate transporter gene family, which is crucial for metabolic dynamic balance and intracellular pH regulation. To further elucidate the role of these expanded MCT genes in response to variable environmental conditions, we conducted a comprehensive genome-wide identification, phylogenetic evolution and expression analysis. In this study, 16 sodium-coupled monocarboxylate transporter genes (designated as ScSMCTs) and 54 proton-coupled monocarboxylate transporter genes (designated as ScMCTs) were identified from the S. constricta genome. The results of gene number comparison indicated significant expansion of ScSMCTs and ScMCTs in mollusks compared to vertebrates, likely due to tandem repeats and dispersed duplications in S. constricta. The syntenic analysis demonstrated that the razor-clam MCT genes had the highest number of homologous gene pairs with Meretrix meretrix. The phylogenetic tree showed that MCT and SMCT proteins were distinctly clustered in two large branches. Moreover, positive selection analysis revealed three positive selection sites in the MCT amino acid sequences sites. Multi-transcriptome analyses and the temporal expression patterns displayed that ScSMCTs and ScMCTs play distinct roles in response to salinity and ammonia stressors. It is worth noting that the majority of these genes involved in abiotic stresses belong to MCTs. Overall, our findings revealed the important roles of ScSMCTs and ScMCTs under abiotic stress, and provided valuable information for the evolution of this family in mollusks, as well as a theoretical basis for the further study of the mechanism and function of this gene family in S. constricta. Full article

The present work aims to evaluate the applicability of mollusk (Meretrix lusoria) shells as a biosorbent for toxic metal ions (Cd²⁺ and Pb²⁺) following the batch mode biosorption procedure. Some well-known analytical methods have been used to characterize the biosorbent such as a scanning electron microscope (SEM), an energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction. The mechanism of metal ion biosorption was examined using various analytical techniques. Therefore, an evaluation of operating factors such as contact time, pH, initial concentration of metal ions, biosorbent dose, and temperature was performed. The results obtained in this investigation indicated that the optimum conditions for the biosorption of Cd⁺² and Pb⁺² ions are as follows: pH = 6; contact times of 90 min; and the 20 mg/L of initial [M²⁺]. And a biosorbent dosage of 1.0 g/100 mL for each metal ion solution was also determined. The maximum removal efficiency results were 90.6% for Cd⁺² and 91.5% for Pb⁺² at pH 6.0. The biosorption isotherm was investigated using three forms of linear equilibrium (Freundlich, Langmuir, and Temkin models). Kinetic studies were also conducted to determine the equilibrium time for the biosorption of the studied metals utilizing the pseudo-second-order, pseudo-first-order, and intraparticle diffusion model. The data indicate that the biosorption kinetics of Cd²⁺ and Pb²⁺ follow the pseudo-second-order models. According to the present study, it can be identified that the shell of Meretrix lusoria is a suitable biosorbent for Cd²⁺ and Pb²⁺ ions and can contribute to their removal from environmentally polluted water. Full article

Obesity is acknowledged as a significant risk factor for cardiovascular disease, often accompanied by increased inflammation and diabetes. Bioactive peptides derived from marine animal proteins show promise as safe and effective anti-obesity agents by regulating adipocyte differentiation through the AMPK signaling pathway. Therefore, this study aims to investigate the anti-obesity and anti-diabetic effects of bioactive compounds derived from a Meretrix lusoria Protamex enzymatic hydrolysate (MLP) fraction (≤1 kDa) through a 6-week treatment (150 mg/kg or 300 mg/kg, administered once daily) in leptin receptor-deficient db/db mice. The MLP treatment significantly decreased the body weight, serum total cholesterol, triglycerides, and LDL-cholesterol levels while also exhibiting a beneficial effect on hepatic and serum marker parameters in db/db mice. A histological analysis revealed a reduction in hepatic steatosis and epididymal fat following MLP treatment. Furthermore, poor glucose tolerance was improved, and hepatic antioxidant enzyme activities were elevated in MLP-treated mice compared to db/db control mice. Western blot analysis showed an increased expression of the AMPK protein after MLP treatment. In addition, the expression of lipogenic genes decreased in db/db mice. These findings indicate that bioactive peptides, which are known to regulate blood glucose levels, lipid metabolism, and adipogenesis, could be beneficial functional food additives and pharmaceuticals. Full article

Cadmium (Cd) is one of the major pollutants in the aquatic environment, and it can easily accumulate in aquatic animals and result in toxic effects by changing the metabolism of the body, causing a serious impact on the immune system, reproductive system, and the development of offspring. The clam Meretrix meretrix is one of the commercially important species that is cultivated in large-scale aquaculture in China. To elucidate the underlying molecular mechanisms of Cd²⁺ in the developmental processes, fertilized eggs and larvae of M. meretrix at different developmental stages were exposed to Cd²⁺ (27.2 mg L⁻¹ in natural seawater) or just natural seawater without Cd²⁺ (control), and high-throughput transcriptome sequencing and immunohistochemistry techniques were used to analyze the toxic effects of Cd on larvae at different early developmental stages. The results revealed 31,914 genes were differentially expressed in the different stages of M. meretrix development upon treatment with Cd²⁺. Ten of these genes were differentially expressed in all stages of development examined, but they comprised only six unigenes (CCO, Ndh, HPX, A2M, STF, and pro-C3), all of which were related to the oxidative stress response. Under Cd exposure, the expression levels of CCO and Ndh were significantly upregulated in D-shaped and pediveliger larvae, while pro-C3 expression was significantly upregulated in the fertilized egg, D-shaped larva, and pediveliger. Moreover, HPX, A2M, and STF expression levels in the fertilized egg and pediveliger larvae were also significantly upregulated. In contrast, CCO, Ndh, HPX, A2M, STF, and pro-C3 expression levels in the postlarva were all downregulated under Cd exposure. Besides the genes with changes in expression identified by the transcriptome, the expression of two other oxidative stress-related genes (MT and Nfr2) was also found to change significantly in the different developmental stages of M. meretrix upon Cd exposure, confirming their roles in combating oxidative stress. Overall, the findings of this study indicated that Cd would interfere with cellular respiration, ion transport, and immune response through inducing oxidative stress, and changes in the expression of oxidative stress-related genes might be an important step for M. meretrix to deal with the adverse effects of Cd at different stages of its development. Full article

This study investigates the impact of various zinc supplementation methods on anemia in rats induced by phenylhydrazine (PHZ) and in 5/6-nephrectomized anemic rats. We compare oral zinc sulfate (ZnSO₄) supplementation, oyster Crassostrea gigas supplementation, and hard clam Meretrix lusoria supplementation on red blood cell (RBC) levels. Oral zinc-rich oyster supplementation (2.70 mg Zn (30 g oyster)/day/rat) effectively corrects anemia in both experimental groups. Rats orally fed oysters for four days exhibit similar effectiveness as those receiving a single ZnSO₄ injection (0.95 mg Zn (4.18 mg ZnSO₄⋅7H₂O)/rat). In contrast, oral ZnSO₄ supplementation (2.70 mg Zn (11.88 mg ZnSO₄⋅7H₂O)/day/rat) does not significantly increase RBC levels, suggesting better zinc absorption from oysters. A placebo group of anemic rats supplemented with hard clams, similar in composition to oysters but much lower in zinc, did not change RBC counts. This supports oysters’ high zinc content as the key to correcting anemia. Oysters also contain high iron levels, offering a potential solution for iron-deficiency anemia while supporting bone marrow erythropoiesis. In summary, oral oyster supplementation emerges as an effective strategy to correct anemia in rats with added zinc and iron support for erythropoiesis. Full article