Search Results (145)

Oyster health is important for aquaculture productivity and sustainability. In Thailand, the white scar oyster, Crassostrea belcheri, is being promoted for cultivation, yet its health status has not been compared between research breeding and community farming sites. This study evaluated histopathological features, ultrastructure, apoptosis, and defender against apoptotic death 1 (dad1) gene expression in sexually mature C. belcheri collected from these two sites. Gill tissues were examined by histology, transmission electron microscopy, TUNEL assay, and gene expression analysis, while organ condition was assessed using a Health Assessment Index (HAI). The proportion of TUNEL-positive cells in the gills and mantle differed significantly between sites (p < 0.05), with higher levels in oysters from the farming site. In contrast, TUNEL-positive cells in the digestive gland did not differ significantly between sites, although brown cells were observed only in the digestive gland of oysters from the breeding site, suggesting possible physiological stress. To assess the expression level of dad1 in oysters cultured under different conditions, RT-qPCR revealed no significant difference between the two sites. The breeding site also had lower temperature and salinity than the farming site. Overall, these findings suggest that site-specific environmental conditions may influence gill health and stress-related responses in C. belcheri, providing baseline information for oyster health assessment and aquaculture management. Full article

As an important aquaculture bivalve, the Pacific oyster (Crassostrea gigas) undergoes a metamorphosis process during its embryonic development. The mortality rate of the eye-spot larva during the metamorphosis and settlement stage is relatively high, which urgently needs to be solved. Glutathione (GSH), as a key antioxidant and immune regulator in organisms, plays an important role in the growth, development, and immune defense of marine invertebrates. Analysis of oyster transcriptome data revealed that the expression of key enzyme-producing GSH, Glutathione S-transferase Kappa 1, reached the highest level at the pediveliger larvae (the stage just before eye-spot larvae), suggesting its important role in the larval settlement process. This study investigated the effects of reduced glutathione supplementation in pediveliger larvae on the settlement metamorphosis and immune capacity of eye-spot larvae. The results showed that high concentrations of glutathione (100 μmol/L, 500 μmol/L) significantly reduced the larval eye-spot rate and settlement rate, with larvae in the 500 μmol/L group nearly all dead after 48 h. Meanwhile, low-concentration GSH (7 μmol/L) could significantly increase the settlement rate of larvae, which was 1.17 times (p < 0.05) that of the control group. When the larvae developed to 1-month-old eye-spot larvae, the survival rate of larvae in the low GSH group significantly increased (38.42 ± 15.98%) after Vibrio splendidus stimulation, while they were almost all dead in the control group. Low GSH could also significantly increase lysozyme LZM activity (by 1.39 times, p < 0.05) and Cu/Zn-SOD activity (by 1.15 times, p < 0.05). Gene expression analysis found that low GSH promoted expressions of larval settlement and metamorphosis-related genes, including ecdysone receptor, P450, and calmodulin. Treatment with low GSH also enhanced the expressions of immune genes of SOD, CAT, and LZM. In summary, a low glutathione supplement can promote the settlement process of oyster eye-spot larvae and enhance disease resistance. These findings reveal the role of glutathione in the metamorphosis and settlement of oyster larvae, providing a scientific basis for optimizing techniques for oyster seedling cultivation. Full article

In Luoyuan Bay, China, Sporobolus alterniflorus invasion has hindered mangrove restoration and disrupted faunal communities within mangrove habitats. This study investigated its impact on mollusk, crab, and fish assemblages across mangrove, mudflat, and invaded habitats from 2019 to 2020. Results showed that species diversity of three assemblages did not differ significantly between invaded and non-invaded mangrove habitats; however, assemblage structure was altered and functional traits declined markedly in invaded areas. Compared with non-invaded mangroves, invaded habitats showed decreases of 81.6% in mollusk density, 50.7% in mollusk biomass, 66.6% in crab density and 84.2% in crab biomass. Dominant fish species (Acanthogobius ommaturus, Liza carinata, Stolephorus chinensis) also exhibited lower body size, total size and biomass in invaded habitats. Given the close dependence of coastal residents on these faunal resources, a socioeconomic analysis of livelihood strategies was conducted, revealing Sinonovacula constricta aquaculture achieved the highest net income-to-investment ratio, 122.7% higher than nearshore fishery and 308.3% higher than shallow-sea oyster cultivation, while professional shellfish farming yielded the highest net income per hectare, 23.6% higher than oyster cultivation. Thus, both forms of shellfish aquaculture provide greater economic returns than other livelihood options. Based on these findings and niche theory, we propose a management framework: after removing S. alterniflorus, plant native mangroves (Kandelia obovata) in mid-to-high intertidal zones and lease lower flats for shellfish farming. This framework has the potential to integrate ecological restoration with local livelihoods and may inform similar efforts in other regions facing biological invasions and restoration challenges. Full article

The physiological performance of the Pacific oyster Magallana gigas in subtropical lagoon systems is shaped by the interaction between environmental variability, reproductive dynamics, and oxidative stress. This study quantified monthly changes in the growth and proximate composition of oysters cultivated in Estero La Cruz, Sonora, and evaluated their relationship with temperature and chlorophyll-a as proxies for thermal stress and trophic availability. Shell growth was continuous, while somatic biomass increased markedly during winter, indicating high thermal tolerance and metabolic flexibility. Proximate composition showed pronounced seasonal oscillations, with energy reserves accumulating during periods of high primary productivity and declining sharply in December, coinciding with peak gametogenic activity. Antioxidant enzyme activities (SOD, CAT, GPx) increased toward winter, reflecting elevated oxidative stress. Correlation and regression analyses revealed consistent relationships among environmental variables and biological responses, identifying temperature as the main factor associated with growth variability. Overall, these results demonstrate a strong coupling between environmental forcing, energy allocation, and oxidative stress, providing an integrative framework for understanding oyster performance and supporting aquaculture management in subtropical coastal systems. Full article

Infestation by boring sponges poses a serious problem for Pacific oyster Magallana gigas (Thunberg, 1793) aquaculture. This study aimed to assess the effect of Pione vastifica sponge infestation on the oysters’ capacity for shell repair, antioxidant defence status, and hemocyte functional state. We analysed the expression of VEGF pathway genes and biomineralisation enzymes, molecular chaperones (Hsp70, Hsp90), growth arrest and DNA damage gene (Gadd45α), antioxidant enzyme activity and lipid peroxidation levels in the hemolymph and various mantle parts (central and outer-edge). Intracellular reactive oxygen species (ROS) levels and mitochondrial membrane potential in hemocytes were evaluated. The results showed that infection significantly increases intracellular ROS levels in hemocytes without changing mitochondrial membrane potential. Oxidative damage was localised primarily in the central mantle contacting the damaged shell. In the outer-edge mantle responsible for shell growth, marked upregulation of SodMn, Cat, and Gadd45α was observed, coupled with suppression of VEGF-R receptor expression and organic matrix genes. Heat shock protein expression decreased in all examined tissues of infected molluscs. Our results demonstrate that shell damage induced by boring sponges triggers a tissue-specific reorganisation of physiological priorities, manifesting as a bioenergetic trade-off where limited energy resources are reallocated from the ATP-demanding process of biomineralisation to sustain antioxidant defence and cell survival. Full article

Blue crab (Callinectes sapidus) populations are of substantial ecological and economic importance. As a keystone species, C. sapidus plays a critical role in maintaining estuarine food webs while also supporting one of the most consumed and economically valuable seafood industries in Delaware and Maryland. This study investigated the presence of Callinectes sapidus reovirus 1 (CsRV1) in C. sapidus collected from Rehoboth Bay, Delaware, USA, using reverse transcription–quantitative polymerase chain reaction (RT-qPCR), and evaluated potential associations between viral occurrence and physicochemical parameters, including temperature, salinity, pH, turbidity, alkalinity, calcium hardness, nitrite, and chlorophyll-a. A total of eighteen traps were deployed across six study sites encompassing oyster aquaculture areas, artificial oyster reefs, and control sites with minimal structural habitat. CsRV1 was detected in blue crabs from Rehoboth Bay, confirming the presence of the virus within the Delaware Inland Bays; however, detections were limited to a small subset of sampled individuals. Among the environmental parameters examined, salinity exhibited the greatest interannual variability, while other physicochemical conditions remained relatively consistent across site types and sampling periods. Overall, environmental conditions during the study period were within ranges considered suitable for C. sapidus, indicating that the population is likely to experience limited environmental stress and minimal disease-related impacts under current conditions. Full article

Oyster aquaculture offers promising opportunities for diversifying marine production in the Romanian Black Sea, where favorable environmental conditions and recent regulatory developments support shellfish farming. This study aimed to generate baseline data for the cultivation of the Pacific oyster, Magallana gigas, through an in situ experimental trial conducted off Mamaia Bay, Romania. A 50 m experimental long-line system was deployed at 13.5 m depth, and triploid oysters were cultured for one year at two depth horizons (3 m and 6 m). The growth performance, meat yield, Condition Index, microbiological quality, environmental parameters, and epibiotic communities were monitored monthly. Cultivation depth significantly influenced oyster growth, with individuals reared at 6 m consistently achieving a greater wet weight and shell length than those at 3 m. Growth rates peaked during spring, and meat yield values indicated good commercial quality. Environmental monitoring showed strong seasonal variability, with high summer temperatures and reduced dissolved oxygen associated with increased mortality. Microbiological analyses revealed higher bacterial loads during warm months. The Condition Index classified the oysters as generally “fine” to occasionally “special”. Overall, the results demonstrate that Black Sea conditions can support successful cultivation of M. gigas, although seasonal environmental stress and epibiosis require appropriate farm management. Full article

The rapid accumulation of fruit and vegetable waste and oyster shell residues presents increasing environmental challenges, particularly in regions with intensive agricultural and aquaculture production. This study evaluated the use of oyster shell powder as a calcium-based buffering additive to stabilize acidic fruit and vegetable waste during rearing of black soldier fly larvae (BSFL, Hermetia illucens). Five substrates containing 0, 2, 4, 6, and 8% oyster shell powder (fresh weight basis) were prepared and used for larval rearing under controlled conditions for 12 days. Substrate pH dynamics, larval growth performance, substrate utilization efficiency, and nutritional composition of larval biomass were assessed. Oyster shell supplementation significantly increased substrate pH in a dose-dependent manner, shifting the substrate from strongly acidic conditions toward the range favorable for larval development. Moderate supplementation levels (2–4%) resulted in the highest larval biomass, survival rate, dry matter reduction, and bioconversion efficiency, whereas excessive supplementation reduced performance. Protein content increased at moderate supplementation levels, while lipid content decreased with higher oyster shell inclusion. Calcium concentration in larval biomass increased proportionally with supplementation, whereas essential amino acid composition remained stable. These results demonstrate that oyster shell powder can be used as an effective buffering material to improve the stability of acidic organic waste substrates and enhance BSFL-based bioconversion. The combined utilization of fruit and vegetable waste and oyster shell residues represents a practical approach for integrated waste valorization and supports the development of circular bioeconomy strategies for sustainable protein production. Full article

Understanding the feeding physiological mechanisms of determined oyster species is fundamental for adaptation and growth stabilization, aiming for gains in aquaculture production. To assess its potential for Integrated Multi-Trophic Aquaculture (IMTA) with shrimp, we analyzed the feeding physiology of the mangrove oyster Crassostrea gasar. In this study, we determined the feeding physiology of the mangrove oyster Crassostrea gasar, a commercially important species in tropical Brazil, under two diets, live microalgae (ISO—Isochrysis galbana) and biofloc (BFT), which were tested at four concentrations (10, 20, 30, and 40 mg L⁻¹), to establish whether this species can effectively utilize BFT as a food source. Results indicated that ISO diet promoted superior filtration, characterized by a higher proportion of feces (F), suggesting a reduced need for intensive particle selection. Both clearance (CR) and filtration (FR) rates peaked at 30 mg L⁻¹ before declining, suggesting a physiological threshold for this diet. In contrast, the BFT diet elicited higher CR and FR values but triggered excessive pseudofeces (PF) production and low net organic selection efficiency (NOSE). This suggests high particle rejection and limited nutritional assimilation. In conclusion, while C. gasar can process BFT, it is metabolically disadvantageous as a sole food source. For an optimal performance, I. galbana concentrations should be maintained at or below 30 mg L⁻¹. Full article

Hypoxia frequently triggers mass mortality events in pearl oysters during the summer months. Hypoxic preconditioning (HP), repeated exposure to sublethal low-oxygen conditions, has been proposed as a potential strategy to enhance stress resistance. Here, we investigated how HP affects hypoxia tolerance in the pearl oyster Pinctada fucata martensii, with emphasis on host apoptotic and immune regulation and the gut microbiota. Pearl oysters assigned to HP (experimental group, EG) and to a non-preconditioned control group (CG) were subjected to sustained hypoxic challenge (1.5 ± 0.1 mg/L DO for 15 days). HP significantly increased the expression of apoptosis- and immunity-related genes (MyD88, IκK, NF-κB) while suppressing JNK expression in gills after extended hypoxia (MyD88: EG 2.26 ± 0.65 vs. CG 0.96 ± 0.29, p < 0.05, ~2.3-fold increase; NF-κB: EG 1.50 ± 0.20 vs. CG 0.81 ± 0.31, p < 0.05, ~1.8-fold increase; IκK: EG 1.55 ± 0.38 vs. CG 0.65 ± 0.12, p < 0.05, ~4.0-fold increase; JNK: EG 0.49 ± 0.25 vs. CG 1.44 ± 0.51, p < 0.05, ~0.34-fold), consistent with a pre-activated yet controlled stress response. In parallel, HP markedly reshaped the intestinal microbial community under hypoxia, increasing alpha diversity (Ace, Chao, and Sobs indices) and enriching potentially beneficial bacterial phyla such as Planctomycetota, Nitrospirota, and Fusobacteriota, groups often linked to nutrient cycling and short-chain fatty acid production. Collectively, these results suggest that HP-enhanced hypoxia tolerance in P. f. martensii is associated with coordinated modulation of host apoptotic and immune signaling and concomitant shifts in gut microbiome diversity. These findings highlight the role of the host–microbiota axis in environmental acclimation and suggest that HP may be a practical tool for improving bivalve performance under hypoxic stress in aquaculture. Full article

Pearl oyster aquaculture is severely constrained by biofouling organisms, particularly fouling oysters, which substantially impair pearl oyster growth and farming efficiency. This study investigated the selective oyster-feeding behavior of the predatory gastropod Thais luteostoma and evaluated its potential as an ecological biofouling control agent in pearl oyster culture. Field co-culture experiments showed that T. luteostoma did not adversely affect the survival of Pinctada fucata martensii, while effectively reducing biofouling loads and significantly improving pearl oyster growth performance. Laboratory behavioral assays and quantitative analyses revealed a pronounced feeding preference for oysters in T. luteostoma, as evidenced by a higher number of feeding individuals, longer total feeding duration, and greater spatial overlap between feeding hotspots and oyster locations. In addition, digestive enzyme assays indicated marked post-feeding physiological responses in T. luteostoma, with a stronger induction of digestive activity in the digestive gland than in the stomach. Collectively, these findings suggest that T. luteostoma represents a promising and sustainable biological option for managing biofouling in pearl oyster aquaculture, with potential applicability to other high-value bivalve farming systems. Full article

Shellfish restoration and aquaculture are considered as innovative methods to mitigate in-water nutrients in coastal waters. Water quality was examined at two oyster aquaculture farms in Potter (2021–2023) and Pt Judith (2023) Ponds in southern Rhode Island, USA. Twice monthly, on a flooding tide, upstream and downstream positions were established and water quality measures were made using fluorometry sondes and laboratory analysis. Significant differences in chlorophyll a, turbidity, and nutrient concentrations between upstream and downstream positions were identified; however, the differences were not consistently greater upstream or downstream. Percent Chl a removed varied from −74% to 64% at Potter Pond among years and −51% to 29% at Point Judith Pond, indicating a deficit or increase in Chl a concentration downstream as compared to upstream over each sampling period. Chlorophyll a measured inside oyster bags was higher compared to the upstream position at Potter Pond, and results from the upstream, downstream, and within farm productivity experiment in both ponds suggest oyster byproducts may facilitate localized and seasonal phytoplankton production. Natural resource managers should consider that while oyster farms in coastal ponds can provide local water clarity through removal of phytoplankton, benefits may be site specific and seasonal. Full article

Lime kiln dust (LKD), a by-product of the paper industry, generates about 100 tonnes of waste per 400,000 tonnes of kraft paper produced, while global aquaculture yields more than 16 million tonnes of oysters annually, 65–90% of which is made up of shells. This study explores their valorisation in the production of more eco-friendly mortars by partially replacing hydrated lime with LKD and oyster shell powder (OSP). In addition, a vinegar solution (VS), prepared by reacting oyster shells with white vinegar (~5% acetic acid), was used as an alternative mixing liquid instead of water. The LKD and OSP were tested at different substitution levels, showing promising mechanical performance, supporting their use as sustainable alternatives in mortar production. Replacement levels of 25%, 50% and 90% achieved compressive strengths ≥ 0.4 MPa at 28 days. At 28 days, the reference lime mortar prepared with water reached 0.83 MPa, while the use of the vinegar solution increased the compressive strength to 1.86 MPa, representing an improvement of approximately 124%. Regarding binder replacement by wastes, the most efficient mechanical performance was obtained for mixtures with 50% LKD substitution, reaching 2.04 MPa at 28 days and 3.11 MPa at 60 days, increasing by 10% and 43%, respectively, while mixtures incorporating oyster shell powder showed more stable mechanical behaviour across substitution levels. Using a hot-mixing process with quicklime in the presence of the vinegar-based solution and sand may account for the higher strengths, due to the heat/steam generated during lime hydration prior to moulding and verified by microscopy. In addition, VS-containing mixes showed higher aragonite contents and detectable phosphorus-bearing compounds, which may further contribute to matrix densification and strengthening. Overall, the results indicate that the combined use of uncalcined calcium-based wastes and a vinegar-based solution can contribute to the development of calcium-based mortars with good mechanical performance, supporting circular economy strategies and the reduction in calcined-binder use in construction materials. Full article

Integrated multitrophic aquaculture (IMTA) emerges as a sustainable strategy to control the excess of solids and inorganic nutrients that tend to increase in the biofloc system (BFT) cycle, since the model integrates organisms from different trophic levels sharing the same system and nutrients. Thus, this study compared a Penaeus vannamei monoculture system with an integrated biofloc system including Mugil liza, Holothuria grisea, Crassostrea tulipa, and Salicornia neei, focusing on water quality and the performance of organisms and systems. This study consisted of three monoculture systems (16 m³; 375 shrimp m⁻³) and three IMTA systems, composed of a shrimp tank (16 m³), a mullet tank (4 m³; 30 ind m⁻³), a combined tank (3 m³) for oysters (45 ind m⁻³) and sea cucumbers (3 ind m⁻²), and a Salicornia neei bed (2.78 m²; 37 ind m⁻²). All IMTA systems operated in recirculation without water exchange, using 10% of the established biofloc inoculum. The IMTA system had half the hydrated lime use (2.13 vs. 4.29 kg), lower solids (299.56 vs. 373.33 mg L⁻¹), and reduced sludge production (9.37 vs. 15.87 kg). Shrimp growth was similar in both systems. Mullet grew adequately with a survival rate of 95.8%, but oysters showed a survival rate of 45.7%. Sea cucumber had a survival rate of 100% until day 28, when a marked decline appeared, strongly correlated with rising temperature (>28 °C; r = −0.71). This resulted in a significant increase in solids in the last weeks, suggesting that the population decline reduces solids control capacity. Furthermore, the biofloc in IMTA was dominated by coccoid forms, with lower proportions of filamentous and cyanobacterial forms. Full article

The bactericidal permeability-increasing protein (BPI) and lipopolysaccharide binding protein (LBP) are fundamental to innate immunity. However, their functional diversity and evolutionary conservation in ecologically crucial invertebrates, such as oysters, remain largely understudied. In this study, we identify and characterize a novel homolog of BPI/LBP, designated as ChBPI/LBP in the Hong Kong oyster (Crassostrea hongkongensis). Through structural and phylogenetic analysis, we identify ChBPI/LBP as a distinct member of the BPI protein family, with a high isoelectric point (pI of 9.26), indicating potent cationic BPI-like bactericidal function. We found that ChBPI/LBP is constitutively highly expressed at mucosal sites such as the gills and is rapidly upregulated in hemocytes following a challenge with Aeromonas hydrophila. Recombinant ChBPI/LBP demonstrated potent and specific bactericidal activity against Gram-negative pathogens. These findings suggest that ChBPI/LBP is an important antimicrobial peptide (AMP) effector in the oyster’s immune response. This work provides novel perspectives on the evolutionary mechanisms of innate immunity in bivalves and may have implications for disease management in aquaculture. Full article