Dietary 5-aminolevulinic acid induces strain-specific effects on shell color and innate immunity in Pacific oyster (Crassostrea gigas) through divergent porphyrin metabolism.

Biochemical Responses of Pacific Oysters (Crassostrea gigas) to Contrasting Oceanographic Environments: Implications of Hydrodynamics, Salinity, and Phytoplankton Communities

An OASL homologue involved in IFN-like antiviral signal by binding MDA5 in the Pacific oyster Crassostrea gigas.

Exploring genomic resistance to coinfection: Single or dual pathogen infection by Ostreid Herpesvirus 1 and Vibrio aestuarianus in Pacific oysters Crassostrea gigas

Enhancing robustness of Pacific oyster (Crassostrea gigas) through breeding strategy based on larval phototaxis

The RNA sensor MDA5 contributes to the antiviral immune response in Crassostrea gigas by modulating the MAVS-mediated signaling pathway.

In the Northern Gulf of Alaska (NGA), the diet of the non-native Pacific oyster (Crassostrea gigas) lacks thorough characterization, despite the species' significant contribution to the state's mariculture industry. Previous observations indicated that C. gigas occupies a higher trophic level than the native Pacific blue mussel (Mytilus trossulus), consuming zooplankton in addition to phytoplankton. Using bulk stable isotopes (δ13C and δ15N), we characterized the spatial patterns in C. gigas resource across five sites in the NGA spanning 300km (Jakolof Bay, Bootleggers Cove, Peterson Bay, Simpson Bay, and Bridget Cove). Individuals of M. trossulus and C. gigas were collected from each site, and in Jakolof Bay, five additional native bivalve species were also examined. C. gigas occupied a higher trophic level than M. trossulus across all sites, and a stable isotope mixing model revealed that zooplankton contributed 29%-94% of C. gigas diet in spring 2024. The isotopic space of C. gigas in Jakolof Bay did not overlap with any of the native clam species, indicating that C. gigas occupies a distinct isotopic niche. Furthermore, C. gigas DNA gut content analysis detected M. trossulus DNA in C. gigas from two of four bays sampled, suggesting that C. gigas consumed M. trossulus larvae. These results indicate that in Alaska, C. gigas may occupy a distinct dietary niche relative to other native bivalves, including predation on bivalve larvae. Impacts of the predation pressure on native species should be closely monitored as mariculture operations expand.

High-resolution paleoenvironmental reconstruction is crucial for understanding past climate dynamics and predicting future climate changes. Holocene oyster reefs (Crassostrea gigas) on the coastal plain of the western Bohai sea serve as valuable archives for deciphering the paleoclimate fluctuations. Micro-scale sclerochronology study of individual oyster shells and macro-scale analysis on reef development can track the different time-resolution paleoenvironmental changes. This study investigated buried Holocene oyster reefs from three sites on the western coast of Bohai Bay: Dawuzhuang (DW), Lingtou (LT), and Huanggang (HG). Multi-proxy approaches, including radiocarbon dating, stable and radiogenic isotopes (C, O, Sr) and morphological analysis, were applied to the oyster shells. In addition, argillaceous sediments in the oyster reefs were analyzed for organic carbon, total nitrogen, total sulfur and their isotopes. Results indicated that the DW reef, characterized by relatively lower δ13C, δ18O, and δ13Corg values, was situated in a proximal estuarine setting with significant freshwater influence. In contrast, the HG reef exhibited higher isotopic values, suggesting minimal freshwater input and higher salinity. The LT reef showed the highest TOC/TN ratio, indicating substantial contributions from freshwater aquatic plants. The DW reef oysters, benefited from high plankton productivity due to terrestrial input, developed broader, thicker, and larger shells. Oysters at the HG reef, lied in a shallow marine area away from the estuary with the high salinity and hydrodynamics, displayed the largest shell height and growth rate but the shortest lifespan. At the LT reef, the low-energy habitat of a lagoon or semi-enclosed bay, fine sediment and reduced sediment stress supported the longest oyster lifespans and slowest shell height and weight growth rate. This integrated analysis of shell and sediment proxies successfully reconstructs distinct paleoenvironmental conditions and ecological adaptations across the Bohai Bay oyster reefs since middle Holocene.

Glutamine enhances Pacific oyster (Crassostrea gigas) larval development through CgEAAT1-cortisol-CgIGF1 signaling pathway

Region-specific metabolomics reveals the mechanisms underlying melanin synthesis in Pacific oyster (Crassostrea gigas) mantle.

CgmiR_n3904-CgHSP68-2 involved in the regulation of unfolded protein response in Crassostrea gigas under high-temperature stress.

Identification of key genes and SNPs associated with the ratio of shell length to shell height in Pacific oyster Crassostrea gigas by whole-genome resequencing

A TNF receptor involved in regulating haemocyte apoptosis by triggering apoptotic factors in the oyster Crassostrea gigas.

Climate change is significantly altering the thermal environment of marine species, causing shifts in animal metabolism through increased temperatures and more frequent marine heatwaves. These changes can impose additional physiological stress on coastal organisms, potentially worsening their sensitivity to environmental pollutants and metabolic disruptors such as plastics. Indeed, nanoplastics are concerning contaminants in marine ecosystems, with the potential to disrupt cellular metabolism and redox balance in aquatic organisms. This study examined if rising temperatures can influence the cellular toxicity of two model polystyrene nanoplastics (non-functionalized Plain-NanoPS and amino-functionalized NH₂-NanoPS) in primary cultures of Pacific oyster Crassostrea gigas (Magallana gigas) hemocytes. We exposed hemocytes to a range of nanoplastic concentrations (0.1 to 10 mg/L) at controlled temperatures from 16 °C to 28 °C and evaluated cellular responses using metabolic, oxidative, and viability biomarkers. This range of concentrations and temperatures reflects the NPs content in tissues and fluids, as well as temperature fluctuations in aquaculture sites and intertidal environments. Plain-NanoPS had minimal effects, while NH₂-NanoPS caused temperature-dependent toxicity, impairing ATP production, reducing metabolic activity, and increasing reactive oxygen species levels. Integrated cellular biomarker analysis showed a shift from an adaptive to a stress-dominated metabolic phenotype under combined NH₂-NanoPS exposure and warming conditions. Since both particle types exhibited similar surface charges in cell culture medium, factors other than surface charge might influence cellular toxicity. This research demonstrates that warming increases the metabolic toxicity of nanoplastics and can reduce the thermal resilience of oyster cells in vitro.

The specifically enhanced immune response of oyster Crassostrea gigas against the secondary encountered same pathogen.

Identification and expression profile of serotonin receptors in the developmental stages and hemocytes of the Pacific oyster (Crassostrea gigas).

Abstract Aging often goes with the deterioration of gamete quality. However, alteration of male sperm quality alongside age is not univocal between species, and this relationship remains largely elusive in bivalve molluscs. Here, we questioned whether ageing attenuates sperm motility and if telomere length (TL), a marker of individual quality, can further mark sperm performance in the Pacific oysters (Crassostrea gigas). We assessed covariation between sperm motility, age and TL in males (n = 45) from 2 to 9 years old. We replicated the measures at four reproductive sessions, corresponding to two types of maturation conditions (controlled in the lab or natural in the field). We found negative correlations between male age and sperm velocity, and slower sperm in natural conditions compared to controlled ones. TL did not shorten with age, but it was positively associated with sperm velocity while maturing under controlled conditions. Our results underscore that sperm swimming performance decreases with ageing, a relationship identified for the first time in a bivalve species. Further research is needed to understand environmental effects and the predictive aspects of telomere dynamics in covarying with sperm quality.

Glycophagy, a selective form of autophagy critical for glycogen homeostasis, relies on the glycogen cargo receptor called starch-binding domain-containing protein 1 (STBD1), yet its evolutionary origins remain elusive. Here, we provide evidence that the Pacific oyster Crassostrea gigas utilizes glycophagy to manage glycogen mobilization during periods of energy deprivation. We identify an oyster STBD1 protein, and trace its origins through phylogenetic and comparative genomic analysis of the carbohydrate binding module family 20 (CBM20) domain within this protein across metazoans. Oyster STBD1 and those in other invertebrates contain an N-terminal CBM20, contrasting the C-terminal location of CBM20 in vertebrate STBD1. N-terminal CBM20 STBD1 proteins have a deep origin in bilaterians, with the vertebrate structural arrangement arising at the chordate root. Structural modelling and functional studies reveal that the N-terminal organization of the CBM20 domain in STBD1 enhances glycogen binding, with subsequent anchoring by GABARAPL2, facilitating an increased glycogen flux into autophagosomes for lysosomal degradation. We conclude that glycophagy is deeply conserved in bilaterians and that STBD1 structural evolution underlies potentially adaptive variation in metabolic strategies across distinct animal clades.

Near-infrared (NIR) spectroscopy is a vital non-destructive analytical tool in the food and aquaculture industries. This study pioneers the application of portable NIR spectrometers for evaluating selenium (Se) content in the Pacific oyster (Crassostrea gigas). We developed quantitative and qualitative models to predict selenium levels in oyster tissue, representing a novel application for monitoring trace elements in marine organisms. Quantitative models were developed using partial least squares (PLS) regression on spectra collected with two portable spectrometers (Micro NIR 1700, Micro PHAZIR RX) and a benchtop FT-NIR instrument, with validation via cross-validation and an independent set. Qualitative models were also constructed to categorize Se content into three levels: 0–1, 1–3, and >3 mg/kg. For quantitative analysis, the Micro NIR 1700 model performed robustly in external validation (RP = 0.932; RMSEP = 0.392; RPD = 2.46). The Micro PHAZIR RX model achieved the highest RC (0.988) and the lowest RMSEC (0.233), yet cross-validation indicated a potential risk of overfitting. In contrast, the FT-NIR instrument yielded the best external predictive ability for powdered samples (RP = 0.954, RPD = 2.60), highlighting its high precision under laboratory conditions. For qualitative discrimination, the Micro PHAZIR RX’s classification module achieved a 100% correct recognition rate (AUC = 0.937). The models based on the Micro NIR 1700 and FT-NIR instruments showed cumulative contribution rates (CCR) of 98.61% and 97.59%, respectively, with high performance indices (PI) of 89.3 and 90.2, confirming their effective discrimination capability. The models established in this study enable the rapid, on-site detection of Se content in oyster samples, underscoring the significant potential of portable NIR spectroscopy for selenium analysis in shellfish.

Marine organisms are continuously exposed to chemical stressors, highlighting the need for operational biomarkers that can be reliably implemented in biomonitoring programmes. Telomere length (TL) has emerged as a promising biomarker of cumulative stress, but its application in ecotoxicology remains limited due to two main challenges: (i) methodological difficulties in obtaining reliable TL measurements from preserved samples, and (ii) incomplete understanding of telomere dynamics across tissues and life stages in sentinel marine species. In this study, we addressed both limitations in the Pacific oyster Crassostrea gigas. First, we compared different DNA extraction methods and selected a protocol suitable for isolating high-molecular-weight DNA from frozen oyster tissues. The qPCR assay was then optimized to minimise technical biases and ensure accurate TL quantification. Using this optimized method, we assessed TL variation across tissues and age classes. Significant tissue-specific differences were observed, with the digestive gland exhibiting the shortest telomeres. In addition, a clear age-related decrease in TL was detected across all tissues. Finally, RT-qPCR analyses revealed lower expression of the telomerase gene in adult tissues compared to early developmental stages, in line with the absence of detectable telomerase activity in adults. Together, these findings provide a methodological and biological framework for future investigations into the effects of chemical stress on telomere dynamics in oysters.