Search Results (895)

Background/Objectives: Ferritins are key iron-sequestering proteins that maintain cellular homeostasis by storing iron in a bioavailable and nontoxic form. They also contribute to innate immunity, cellular proliferation and differentiation, shell formation, and protection against oxidative stress. In this study, we identified and characterized the M-type subunit of ferritin (Mbi-Fer) from the Indian backwater oyster, Magallana bilineata (Röding, 1798). Methods: A full-length cDNA of Mbi-Fer was sequenced and analyzed, and its gene expression was quantified in oysters collected from their natural habitat. Additionally, the coding region of Mbi-Fer was transformed and expressed in Escherichia coli, and the recombinant protein was purified and analyzed. Results: Mbi-Fer exhibited all the typical features of M-type ferritins, including the ferroxidation site of the H subunit and the nucleation core of the L subunit. The amino acid sequence alignment and phylogenetic analysis showed high similarity to the M-type ferritin subunits of Magallana gigas (Thunberg, 1793). A putative iron-responsive element was identified in the 5′ UTR, indicating potential post-transcriptional regulation. Mbi-Fer expression in wild oysters was increased by more than fourfold, relative to laboratory-maintained control oysters. The recombinant expression result revealed a unique protein band that was specific to a ferritin M-like subunit, with an approximately molecular weight of 20 kDa. Conclusions: Our findings suggest that Mbi-Fer may play a role in both the iron storage and shell formation of backwater oysters and may serve as a valuable molecular marker of oxidative and environmental stress responses in estuarine bivalves. Full article

The Manila clam Ruditapes philippinarum is a commercially important bivalve worldwide, with China being the leading producer. While the reproductive biology of this species has been extensively studied in its native or long-established ranges, knowledge of how populations cultured from non-native seed sources adapt their reproductive cycles to new environmental conditions remains limited. In this observational study, we investigated the annual reproductive cycle of a Manila clam population originating from subtropical waters (Zhejiang Province, Southern China) that was cultured in temperate aquaculture grounds in Zhuanghe Bay, Northern China. Monthly histological examination of 50 clams demonstrated that the gametogenic cycle synchronized between male and female clams. Gametogenesis started in March when seawater temperature exceeded 5.7 °C, and most gametes matured by May. A distinct bimodal spawning pattern was observed: a minor spawning event occurred from May to July, followed by a major spawning phase from September to November after a one-month gonadal recovery period in August. The condition index (CI), analyzed monthly in 30 clams, effectively reflected reproductive stages, increasing during gametogenesis and declining sharply during spawning, with its amplitude indicating spawning intensity. Seawater temperature was identified as the primary regulatory factor driving reproductive development from gametogenesis to spawning, while food availability (indicated by chlorophyll a concentration) played a crucial role in supporting gonadal recovery during summer. These results align with observations in other temperate populations, demonstrating that subtropical-origin clams can successfully acclimate their reproductive cycles to temperate environmental conditions. This study provides the first comprehensive description of the reproductive biology of transplanted Manila clams in Northern China, offering critical benchmarks for optimizing hatchery production schedules and informing sustainable fishery management practices in the region. Full article

Metamorphosis is a critical bottleneck in the bivalve life cycle, usually associated with high mortality and asynchronous development under hatchery conditions. Synthetic chemical inducers are widely used to overcome these constraints. The neuroactive compounds epinephrine (EPI) and γ-aminobutyric acid (GABA) have been reported to be effective metamorphosis inducers in bivalve species. This study evaluated the inductive efficiency and toxicity of EPI and GABA in two economically important clam species, Venerupis corrugata and Ruditapes decussatus. Competent larvae were exposed to different concentrations (10⁻², 10⁻⁴ and 10⁻⁶ M) for 24, 48 and 72 h. Metamorphic progression and mortality were assessed immediately after exposure and following a six-day post-exposure period. Both compounds induced metamorphosis following concentration–time and species-dependent responses, with narrow efficiency windows and pronounced delayed mortality at higher concentrations and/or longer exposure durations. In V. corrugata, the highest metamorphosis rates were obtained with both compounds at 10⁻⁶ M after 48 h. In contrast, R. decussatus required higher EPI concentrations (10⁻⁴ M for 48 h) for optimal induction, while GABA at 10⁻⁶ M was effective after 24 and 48 h. These findings highlight the need for post-exposure assessments and species-specific optimisation of chemical induction protocols to improve metamorphosis success and spat production in bivalve hatcheries. Full article

The Portuguese Water Quality Policy, aligned with the Water Framework Directive, requires the monitoring of shellfish production in coastal and brackish water bodies and is based on the EC Shellfish Waters Directive; it preserves the environmental conditions necessary for shellfish growth and contributes to the production of a safe, high-quality sustainable animal food source. Between 2017 and 2021, quarterly measurements of physico-chemical and microbial parameters were conducted at 11 coastal stations and 21 estuarine/coastal lagoons stations along Portugal, to evaluate shellfish water quality and identify the environmental drivers influencing it. Results showed that estuaries and coastal lagoons were more vulnerable to fluctuations in salinity, oxygen and suspended matter and consistently exhibited higher faecal contamination in bivalves than coastal waters. These patterns were shaped by freshwater inputs, climate-driven variability, and local anthropogenic pressures, with contamination often increasing during rainy periods or under stressful environmental conditions. The study highlights the sensitivity of transitional waters to both natural and human-induced changes and underscores the need for targeted management strategies, such as improved wastewater treatment and integrated coastal management, to reduce pollution pressures. Strengthening these measures is essential for the long-term sustainability of Portugal’s shellfish industry and coastal ecosystems. 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

The co-occurrence of ammonia nitrogen and hypoxia represents a physiologically taxing synergistic challenge for benthic bivalves—as it forces a conflict between the high energy demand for detoxification and the limited energy supply under low oxygen, yet the tissue-specific strategies underlying their resilience remain poorly understood. This study investigated the physiological and transcriptomic responses of the razor clam Sinonovacula constricta to ammonia (AG), hypoxia (HG), and their combination (HAG) over 96 h. Transcriptomic profiling revealed that the gill and hepatopancreas employ distinct, organ-coordinated adaptive strategies rather than a uniform systemic response. The gill prioritized respiratory homeostasis by fine-tuning oxygen sensing: transcriptional suppression of hypoxia-inducible factor 1-α (HIF-1α) (to limit glycolytic acidosis) was followed by a chronic induction of HIF-2α, alongside the specific upregulation of the mitochondrial respiratory gene cytochrome c oxidase-6b (COX-6b). In contrast, the hepatopancreas executed a critical metabolic trade-off centered on arginine metabolism. Under combined stress, arginine flux was redirected toward the urea cycle via a robust upregulation of arginase (ARG) for detoxification, while nitric oxide synthase (NOS) was concurrently suppressed. This reciprocal regulation suggests a strategy to prioritize ammonia clearance and energy conservation at the expense of immune signaling. These findings elucidate how S. constricta navigates the bioenergetic conflict between detoxification and oxygen limitation, providing molecular targets for breeding stress-resistant aquaculture strains. Full article

Synthetic or plastic microfibers (MFs) are an emerging form of microplastic pollution in marine ecosystems, derived from textile degradation and weathering of fishing and aquaculture gear. Despite extensive evidence of MFs in marine organisms, the effects of MFs exposure on mussels remain poorly understood. This study investigated the impact of synthetic MFs on the mussel Mytilus galloprovincialis (Lamarck, 1819) over a semi-chronic time scale of 14 days, using MFs produced by grinding a microfiber cloth. Adult mussels were exposed to three MFs treatments: 8, 40, and 100 MFs/L, reflecting current and future scenarios in the Black Sea. Biomarkers assessed included lysosomal membrane stability (LMS), catalase (CAT), glutathione-S-transferase (GST), and acetylcholinesterase (AChE) activities. Significant lysosomal membrane destabilization (p < 0.05) occurred across all treatments. CAT activity in the digestive gland significantly decreased by 31.2%, 53.3%, and 62.1% at 8, 40, and 100 MFs/L, respectively. GST activity showed inhibition at 8 and 100 MFs/L and stimulation at 40 MFs/L. AChE activity decreased at 8 MFs/L but increased at higher concentrations. These results indicate that even environmentally relevant levels of synthetic MFs can alter cellular stability and enzymatic responses in mussels, suggesting potential ecological risks for marine bivalves. Full article

The European green crab (Carcinus maenas) is an intertidal crustacean that has extended its invasive range globally and is regarded as a major pest species for bivalves, impacting coastal food chains and aquacultures. Crabs primarily use chemosensory cues to sense their environment for feeding to avoid predation and to locate mates and induce mating. Consequently, known attractants including food baits are frequently employed in trapping and control efforts. Here, we investigate the effects of introducing a predatory fish odour to the environment and show that it elicits anti-predator behaviour in C. maenas. A 45% reduction in crab foraging and feeding behaviour was observed when predator odour was introduced compared with food control experiments. A further 23% reduction (68% reduction overall) in feeding behaviour was observed after crabs were exposed to (though housed separately from) the same seawater as the live predator for several days. This highlights the increased awareness or continuous stress of these habituated crabs towards predator odour. This study also presents potential for application as a deterrent in integrated pest management strategies for this global invader. Full article

Marine lectins function as pattern recognition receptors in innate immunity through carbohydrate-binding mechanisms. However, mechanistic evidence detailing intracellular signaling cascades (e.g., MAPK/NF-κB/JAK-STAT activation linked to defined cytokine outputs) remains taxonomically uneven. Bivalve mollusks—particularly the Mytilectin family—represent the most extensively characterized group, whereas lectins from other marine phyla (echinoderms, cnidarians, fish, algae) have been studied primarily for structural and glycan-binding properties alongside phenotypic antimicrobial outcomes. Signaling-level resolution in native immune-cell contexts, while present in some cases, remains comparatively limited. This review synthesizes mechanistic insights dominated by bivalve-derived lectins, while integrating cross-taxa comparisons at evidence-supported levels. Specific bivalve lectins induce macrophage activation and pro-inflammatory cytokine production through reactive oxygen species-dependent activation of key signaling pathways including MAPK, NF-κB, and JAK-STAT cascades. These lectins exhibit context-dependent properties, promoting inflammatory responses in resting cells while inducing endotoxin tolerance in pre-activated macrophages through epigenetic reprogramming. Functional outcomes include broad-spectrum antiviral activity through viral envelope glycoprotein binding, anti-inflammatory effects in pain models, and cancer-associated immune responses through tumor glycan recognition and macrophage polarization. Critical gaps include uncharacterized effects on adaptive immunity, limited understanding of dendritic cell and natural killer cell interactions, and incomplete evaluation of cancer immunotherapy potential. Future research should prioritize mechanistic characterization of marine lectin-based immunotherapeutics. 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

New Zealand green-lipped mussel (Perna canaliculus) is a premium seafood product that may be substituted with morphologically similar mussels after shucking and cooking, particularly Asian green mussel (Perna viridis). This study developed a rapid, on-site duplex recombinase-aided amplification–lateral flow dipstick (dRAA–LFD) assay to authenticate P. canaliculus and differentiate it from P. viridis. Species-specific primers were designed from mitochondrial COI alignment and combined in a dRAA reaction. Reaction conditions were optimized at 37–42 °C and 15–60 min. Specificity was assessed against 11 non-target seafood species, and sensitivity was evaluated using 2-fold serial dilutions. The assay was further validated using DNA from boiled (85 °C, 5–15 min), steamed (105 °C, 10–30 min), and fried (185 °C, 30–90 s) mussels, and 15 restaurant products labeled as New Zealand mussel dishes. Optimal performance was achieved at 40 °C for 30 min, with no cross-reactivity. The LFD detection limits were 0.05 ng/reaction for P. viridis and 0.2–0.1 ng/reaction for P. canaliculus. All cooked samples remained identifiable, and commercial testing classified 13/15 products as P. canaliculus and 2/15 as P. viridis. Overall, the dRAA–LFD assay enables rapid, equipment-light authentication of cooked mussel products for routine screening. Full article

The Chi River Basin in northeastern Thailand is the country’s second-largest basin and a major tributary of the Mekong River, which is a regional hotspot for freshwater mollusc diversity. However, many of its sub-tributaries remain poorly studied. This study investigated molluscan diversity in the upper Chi River and examined relationships between assemblage structure and physicochemical habitat factors. Quantitative quadrat sampling was conducted at 11 stations along a 100 km reach, and community–environment linkages were analyzed using cluster analysis and canonical correspondence analysis (CCA). A total of 2734 individuals representing 25 taxa (12 gastropods, 13 bivalves) were recorded. Three distinct assemblages—Upstream, Midstream, and Downstream—were identified along the longitudinal gradient. CCA indicated that flow velocity, total dissolved solids (TDS), and dissolved oxygen (DO) were the primary predictors of assemblage structure (p < 0.01), jointly explaining 59.5% of community variation. Upstream reaches were dominated by Thiaridae (Tarebia, Brotia), midstream sections by Corbicula, and downstream areas exhibited the highest diversity, characterized by large unionid mussels. This study provides the first quantitative evidence of clear longitudinal zonation in the upper Chi River and establishes essential baseline data for conservation and management in this overlooked, biodiversity-rich basin. Full article

The climate impact of bivalve aquaculture remains inadequately quantified for China, the world’s dominant producer. Prevailing carbon footprint assessments often overlook the complexity of biological carbon flows and fail to capture effects that evolve across different timescales. To address these gaps, we developed a novel multi-temporal dual-carbon flow life cycle assessment framework that systematically quantifies both the anthropogenic (ACF) and biological (BCF) carbon footprints and evaluates the climate impacts across different time horizons. Applied to China’s largest mussel farm, the framework reveals the system’s total carbon footprint decreases from +261.7 kg CO₂-eq/t under a conventional Cradle-to-Gate perspective to +84.6 kg CO₂-eq/t over a centennial scale and further to +27.9 kg CO₂-eq/t over a geological timescale. With the ACF constant across all timescales (+256.2 kg CO₂-eq/t), the transition in total carbon footprint is driven entirely by the BCF. The BCF changes from a minor positive contribution during farming (+5.5 kg CO₂-eq/t, from enhanced sea-to-air CO₂ efflux) to a major net sink at centennial (–171.6 kg CO₂-eq/t ) and geological (–228.3 kg CO₂-eq/t) scales, primarily due to long-term carbon sequestration from shell removal, burial, and weathering. Consequently, the net carbon footprint is not a fixed attribute but a function of temporal perspective, controlled decisively by shell-waste management. Aligning the industry with climate goals thus requires not only reducing the ACF through material and energy efficiency during the production chain but, crucially, also diverting shells from incineration to burial or weathering pathways to secure their long-term sink potential. Full article

A new species of pectinid bivalve, Syncyclonema goyi sp. nov., is described in honour of Professor Antonio Goy, one of the leading stratigraphers who shaped Mesozoic studies in Iberia over the past half century. It represents one of the smaller fossil scallops currently known from the Upper Cretaceous of Europe, alongside a few boreal species previously assigned to the family Entoliidae. The type specimens have orbicular valves, almost smooth, with unequal auricles. The right valve is more convex and bears a well-marked paleal sinus. The sculpture of the shell is weak, exhibiting concentric growth lines and lamellae. However, nearly 90 very small, uniform radial striae are discernible beneath the outer shell layer. This species is frequent in open marine, fine-grained, inner shelf facies of the Tethyan West Portuguese Carbonate Platform, near the main localities of Coimbra, Tentúgal, and Condeixa-a-Nova, in the Baixo Mondego region of West Portugal. It mostly occurs in the upper Cenomanian beds of the Trouxemil Formation, with Euomphaloceras septemseriatum and Vascoceratidae ammonites. Full article

Bivalves possess a diverse array of photoreceptive organs that are significant for their evolutionary success and systematic classification. Giant clams are the largest bivalve mollusks, with mantle tissue permanently extended in nature to maintain symbiosis with zooxanthellae and perceive environmental cues. Eyes serve as critical sensory organs for these organisms, yet the structural and functional characteristics of tridacnine eyes remain inadequately understood. This study systematically investigated the ocular traits and visual resolution of three ecologically distinct giant clam species (Tridacna crocea, T. squamosa, T. maxima) using morphometric analysis, hematoxylin-eosin (HE) staining, transmission electron microscopy (TEM), and grating stimulation assays. Significant interspecific differences were observed in eye count, diameter, and pupil-to-eye ratio (PER): T. maxima exhibited the highest mean eye count (221 ± 8), T. squamosa the largest mean eye diameter (0.490 ± 0.082 mm), and T. crocea the highest mean PER (0.363 ± 0.041). Eyes were numerically symmetric on the left and right mantles but positionally asymmetric, showing random distribution patterns along the mantle margin without fixed corresponding locations across species. All three species possessed typical pinhole eyes lacking lenses and retinas, primarily composed of filler cells, receptor cells, and sparse neurons, with symbiotic zooxanthellae distributed in the surrounding mantle tissue. Grating stimulation assays revealed resolvable stripe periods of 5.82–11.64° (T. crocea), 8.62–13.16° (T. squamosa), and 10.15–12.26° (T. maxima), confirming T. crocea as the species with the highest visual resolution. These ocular variations are inferred to reflect adaptive evolution driven by ecological niches and habitat-specific factors (water depth or light intensity), while the simplified pinhole morphology is consistent with their sedentary lifestyle and metabolic dependence on symbiotic zooxanthellae. These ocular variations provide potential morphological markers for the systematic classification of Tridacninae and offer valuable insights for researchers studying the evolutionary plasticity of bivalve visual systems. Full article