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Rationale: Stable carbon and oxygen isotope data of biogenic and abiogenic aragonite are of fundamental relevance in paleoclimate research. Wet‐chemical analysis of such materials requires well‐homogenized, fine‐grained powder. In the present study, the effect of different grinding/milling methods on sample homogeneity and the potential risk of unintentional calcite formation and isotope shift were evaluated. Methods: Shells of Arctica islandica and aragonite sputnik crystals were pulverized using a set of commonly used methods, including a hand‐held drill, a vibromill operated at various settings (with and without liquid nitrogen cooling, changes in ball diameters, frequencies, and processing durations), and an agate mortar and pestle. Stable isotope values were measured using an isotope ratio mass spectrometer operated in continuous flow mode. Identification of mineral phases was obtained by powder X‐ray diffraction (PXRD), Raman spectroscopy, and attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR) spectroscopy. Calcite content was quantified by PXRD Rietveld refinement. Results: Samples showed substantial homogeneity, in particular after vibromilling (duration 3–10 min). More vigorous grinding resulted in larger fractions of calcite (0.5–4.2 wt%) and a concomitant δ18O and δ13C decrease, specifically in bivalve shells. The only method for producing pure aragonite powder was by pounding the aragonite sputniks manually with an agate mortar and pestle. Conclusions: None of the studied, commonly used machine‐based pulverization methods produced pure aragonite powder from samples consisting originally of aragonite. These findings have significant implications for light‐stable isotope‐based paleoclimate reconstructions. Except for abiogenic aragonite powder produced by pounding in an agate mortar, paleotemperatures would be overestimated. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is a toxic heavy metal that, when present as a pollutant in the marine environment, is readily accumulated by marine bivalves, causing oxidative stress and tissue damage. This study explored whether short-term depuration could reverse Cd2+-induced toxicity in the ovary of the clam Meretrix meretrix. Clams exposed to 3 mg L-1 Cd2+ for three days showed increased accumulated Cd2+ in their ovaries with obvious tissue damage as shown by loose structure and some apoptotic cells compared with non-exposed clams. Increased oxidative stress in the ovarian tissue was also obvious, as revealed by increased levels of oxidative indicators such as reactive oxygen species (ROS), malondialdehyde (MDA), DNA-protein crosslinking (DPC), and protein carbonylation (PCO) and increased expression levels of genes related to oxidative stress and apoptosis, which included the Bax, Bcl-2, caspase-3, HO-1, Hsp70, NQO1, Nrf2, and MT genes. When the clams were exposed to Cd2+ for three more days, the accumulated Cd2+ level in the ovary increased to more than 10-fold the level in the control clams, accompanied by more severe damage and cell death as well as oxidative stress. However, when the initial three-day Cd2+ exposure was followed by three days of depuration in Cd2+-free seawater, the Cd2+ level in the ovary was reduced by as much as 20%, accompanied by some recovery of tissue damage and reduced oxidative stress, suggesting that short-term depuration may mitigate Cd2+-induced toxicity in M. meretrix, allowing the clams to recover and potentially reducing the risk of Cd2+ exposure from consuming contaminated clams. [ABSTRACT FROM AUTHOR]

The encrusted bivalve steinkerns in the Upper Ordovician of Estonia suggest that the rapid sea-floor cementation facilitated the early lithification of the sediment within the bivalve shell and the shell valves, likely aragonitic in composition, were dissolved due to calcite sea conditions similarly to many other regions in the Ordovician. The abandoned bivalve shells contained cryptic invertebrates. The coelobite fauna was dominated by encrusting brachiopods, followed by bryozoans and cornulitids. The bryozoans and cornulitids do not prefer specific regions of the shell interior, indicating that the waters within the shell were sufficiently nutrient-rich throughout. Encrusting brachiopods are always confined to valve margins, suggesting that the waters were nutrient-rich enough for the brachiopods only at the edge of the outer environment. Thus, it is possible that bryozoans and cornulitids were better adapted for a cryptic life than the encrusting brachiopods in the Late Ordovician of Estonia. [ABSTRACT FROM AUTHOR]

Understanding the developmental processes and signaling pathways involved in larval myogenesis and metamorphosis is crucial for comprehending the life history and adaptive strategies of marine organisms. In this study, we investigated the temporal and spatial patterns of myogenesis in the mussel Mytilus coruscus (Mc), focusing on the emergence and transformation of major muscle groups during different larval stages. We also explored the role of the Hedgehog (Hh) signaling pathway in regulating myogenesis and larval metamorphosis. The results revealed distinct developmental stages characterized by the emergence of specific muscular components, such as velum retractor muscles and anterior adductor muscles, in D-veliger and umbo larvae, which are responsible for the planktonic stage. In the pediveliger stage, posterior ventral, posterior adductor, and foot muscles appeared. After larval metamorphosis, the velum structure and its corresponding retractor muscles degenerate, indicating the transition from planktonic to benthic life. We observed a conserved pattern of larval musculature development and revealed a high degree of conservation across bivalve species, with comparable emergence times during myogenesis. Furthermore, exposure to the Hh signaling inhibitor cyclopamine impaired larval muscle development, reduced larval swimming activity, and inhibited larval metamorphosis in M. coruscus. Cyclopamine-mediated inhibition of Hh signaling led to reduced expression of four key genes within the Hh signaling pathway (McHh , McPtc , McSmo , and McGli) and the striated myosin heavy chain gene (McMHC). It is hypothesised that the abnormal larval muscle development in cyclopamine-treated groups may be an indirect effect due to disrupted McMHC expression. We provide evidence for the first time that cyclopamine treatment inhibited larval metamorphosis in bivalves, highlighting the potential involvement of Hh signaling in mediating larval muscle development and metamorphosis in M. coruscus. The present study provides insights into the dynamic nature of myogenesis and the regulatory role of the Hh signaling pathway during larval development and metamorphosis in M. coruscus. The results obtained in this study contribute to a better understanding of the evolutionary significance of Hh signaling in bivalves and shed light on the mechanisms underlying larval muscle development and metamorphosis in marine invertebrates. [Display omitted] • Studied larval myogenesis with specific muscle emergence and degeneration in Mytilus coruscus. • Identified conserved patterns of larval musculature across bivalve species. • Hh signaling inhibitor cyclopamine inhibited larval muscle development and larval metamorphosis. • Cyclopamine inhibited the expression of key genes within the Hh signaling and a myosin gene. [ABSTRACT FROM AUTHOR]

The motivation for constructing a thin-shell wormhole from a (2+1)-dimensional rotating black hole arises from the desire to study the effects of a nonminimally coupled scalar field in this particular spacetime. By investigating the behavior of such a field in the presence of rotation, we can gain insights into the interplay between gravity and scalar fields in lower-dimensional systems. Additionally, this construction allows us to explore potential connections between black hole physics and exotic phenomena like traversable wormholes. The radial perturbation around the equilibrium throat radius is considered to explore the stable configuration for specific values of physical parameters. Then, the equations of state, specifically the phantom-like and generalized Chaplygin gas model for exotic matter is used to conduct an extensive investigation into the stability of the counter-rotating thin-shell wormholes. Our results show that the presence of a scalar field enhances the stability of the counter-rotating thin-shell wormholes. [ABSTRACT FROM AUTHOR]

The bivalve mollusc Arctica islandica can live for hundreds of years, and its shell has provided a valuable resource for sclerochronological studies and geochemical analyses for understanding palaeoenvironmental change. Shell specimens recovered from the seabed need to be dated in order to aid sample selection, but existing methods using radiocarbon dating or cross-dating are both costly and time-consuming. We have investigated amino acid geochronology (AAG) as a potential alternative means of providing a less costly and more efficient range-finding method. In order to do this, we have investigated the complex microstructure of the shells, as this may influence the application of AAG. Each of the three microstructural layers of A. islandica have been isolated and their protein degradation examined (amino acid concentration, composition, racemization, and peptide bond hydrolysis). The intra-crystalline protein fraction was successfully extracted following oxidation treatment for 48 h, and high-temperature experiments at 140 °C established coherent breakdown patterns in all three layers, but the inner portion of the outer shell layer (iOSL) was the most appropriate component due to practicalities. Sampling of the iOSL layer in Holocene shells from early and late ontogeny (over 100–400 years) showed that the resolution of AAG is too low in A. islandica for within-shell age resolution. However, analysis of 52 subfossil samples confirmed that this approach could be used to establish a relative geochronology for this biomineral throughout the whole of the Quaternary. In the late Holocene the temporal resolution is ∼1500 –2000 years. Relative dating of 160 dredged shells of unknown age was narrowed down using AAG as a range finder, showing that a collection of shells from Iceland and the North Sea covered the middle Holocene, late Holocene, later and post-medieval (1171–1713 CE), and modern day. This study confirms the value of A. islandica as a reliable material for range finding and for dating Quaternary deposits. [ABSTRACT FROM AUTHOR]

Chamid bivalves are marine organisms that live in high-energy environments and are cemented to hard substrates. To avoid shell damage, the organisms form thick, densely ornamented shells. Shell material consists of aragonite, and the ornamentation may be either aragonitic or calcitic. The latter can be developed as scaly spines, rows of blades, or comarginal, radial arched lamellae. We investigated biological crystal morphology and mode of assembly of Chama arcana and Chama gryphoides shells. Structural characteristics were obtained from electron backscatter diffraction (EBSD) measurements, complemented with laser confocal and BSE imaging. We found a wide range of crystal morphologies and sizes, ranging from irregularly shaped calcite and/or aragonite prisms to tiny and thin aragonite laths. We observed four different modes of crystal assembly patterns: 1. strongly interlocked dendritic calcite units forming the ornamentation blades; 2. aragonite laths arranged to lamellae forming the outer shell layer, the layer adjacent to the calcite; 3. aragonite laths arranged into blocks comprising inner shell layers or aragonitic ornamentations; and 4. shell portions consisting of aragonite prisms, structured in size and crystal orientation, at muscle attachment sites. These four different types of crystal arrangements were observed for the shells of the investigated chamid species; however, they had slightly different strengths of structuring and slight variations in crystal organisation. Additionally, we observed unique microstructural features in Chama shells: We report ornamentation crystals resembling idiomorphic calcite and novel, twinned entities found at the changeover between the aragonitic layers. We highlight and discuss these differences and anomalies in this contribution. [ABSTRACT FROM AUTHOR]

Neuromodulation stands as a cornerstone in the therapeutic landscape for neurological disorders, yet the quest for selective stimulation of specific brain regions with minimal invasiveness and high spatiotemporal precision remains a formidable challenge. In this study, a multifunctional nano‐optical electrode (NOE) to mitigate depressive symptoms in animal models of depression is introduced. The NOEs' core–shell architecture integrates mesoporous carbon shells for optimal absorption of near‐infrared (NIR) light, alongside superparamagnetic ferric oxide nanocluster cores for magnetic resonance imaging (MRI) visibility. This configuration enables the precise excitation of untransfected neurons using NIR irradiation. The MRI‐guided NIR neuromodulation via NOEs can significantly alleviate depressive symptoms in mice. This is evidenced by the observed enhancement in pleasure‐seeking behaviors, improved motor functions, and a decrease in behaviors indicative of despair. The alleviation of depressive symptoms is ascribed to the NOEs' role as an efficient NIR light transducer, which boosts neuronal activity in the medial prefrontal cortex (mPFC). The MRI compatibility of the NOEs augments the spatial resolution, further refining the precision of neuromodulation. The multimodal, precise, transcranial, and non‐genetic approach of the NOEs‐based neuromodulation strategy heralds a new era in the optical‐theranostics of neurological disorders. [ABSTRACT FROM AUTHOR]

In order to screen out the feeding ratio of high‐quality algae strains in Hyriopsis cumingii, this experiment investigated the effects of different ratio of mixed feeding of two algae strains (Scenedesmus dimorphus and Cyclotella sp.) on the growth, bead production performance, trace elements, and amino acid composition of the newborn shell of H. cumingii. The results showed that the mixed feeding of two types of microalgae with different densities had significant effects on the growth performance, bead production quality, trace elements, and amino acid composition of the newly formed shell of H. cumingii (p < 0.05); the best body weight gain rate and shell growth rate were obtained by feeding S. dimorphus (30 × 105 cell/mL) and Cyclopella sp.(8 × 105 cell/mL); the pearl weight gain rate, amino acid ratio, Ca2+ and Mn2+ content were best when feeding Cyclotella sp. (16 × 105 cell/mL), but there was no significant difference compared with S. dimorphus (30 × 105 cell/mL) and Cyclopella sp.(8 × 105 cell/mL). In summary, the optimal feeding amount for the intensive breeding process of H. cumingii is S. dimorphus (30 × 105 cell/mL) and Cyclopella sp. (8 × 105 cell/mL). [ABSTRACT FROM AUTHOR]

In this study, the chemical composition of Mytilus galloprovincialis shells was examined. As known, the main component of shell composition in bivalves is calcium carbonate, which constitutes approximately 94% of the shell. The zero charge points (PZC) of the shells were determined in the study. The PZC value indicates the surface charge state of the shells. The PZC value of the shells was determined to be 8.39. The PZC value of the shells provides important information for the characterization and potential applications of the shells. SEM images and EDS analyzes of the shells were made. According to the EDS results, calcium, carbon, and oxygen atoms belonging to the main structure of calcium carbonate (CaCO3) appeared in the highest proportions. FT-IR analysis was supported to the calcium carbonate (CaCO3) structure. XRD analyses were performed within the scope of the study, and it was determined that the shell structures mainly consist of a mixture of calcium carbonate and aragonite. In conclusion, this study on the chemical composition of M. galloprovincialis shells provides a detailed analysis of shell composition. The analyses conducted provide important information about the chemical composition, structural properties, and potential applications of the shells. This study contributes to research on the biological and chemical properties of marine organisms and is considered to form the basis for future studies. [ABSTRACT FROM AUTHOR]

The Sr/Ca and 87Sr/86Sr ratios are used as natural indicators (geomarkers) in fish to reveal migratory patterns, due to significant relationships between these ratios measured in the water and in the fish calcified structures (otoliths, bones). The aim of this study was to assess the potential use of the Limnoperna fortunei shell as a proxy for monitoring the spatial and temporal variability of Sr/Ca and 87Sr/86Sr in water. These ratios were compared in water samples and bivalve shells proceeding from eight sites of four hydrogeological regions of the La Plata Basin (Argentina and Uruguay), collected in two hydrological periods (winter and summer) in order to depict the pattern of geographical and temporal variability and to evaluate the relationship between both matrices. Significant positive linear relationships were found between shell edge and water for 87Sr/86Sr (R2 = 0.96–0.97, p < 0.005) and Sr/Ca (R2 = 0.83–0.86, p < 0.05) in summer and winter. Slopes did not differ significantly from 1 (p > 0.05) for 87Sr/86Sr, while they differed from 1 for Sr/Ca in both seasons (p < 0.05), indicating that the elemental ratio would be influenced by endogenous/exogenous factors. No significant seasonal differences were found for both natural tags (p > 0.05), except for the lower Uruguay River (87Sr/86Sr) and outer estuary (Sr/Ca). These results indicate that the L. fortunei shell could be a valuable tool for monitoring spatio-temporal variations in water 87Sr/86Sr. Shell Sr/Ca shows high potential utility as a geomarker in freshwater, but additional assessments are needed to understand the impact of temperature and growth on this ratio. [ABSTRACT FROM AUTHOR]

Understanding the motion thresholds of shells is important, as shell motion allows the analysis of beach profiles, prevents excessive erosion of the coastline, and helps to resource the use of discarded shells, providing new ideas for the protection of beaches. In this study, the orientational motions and motion thresholds of two types of typical molluscan shells, bivalve and gastropod shells, were investigated by means of flume experiments. The final orientations with the statistically highest number of occurrences during the orientational motions of each shell were used as the initial orientations for the respective threshold flow velocity measurements. The critical Shields parameter and the incipient mean velocity of the flow were used to represent the critical threshold of the motion. The critical Shields parameters for bivalve shells in the convex upward position were overall higher on average than those for gastropod shells. The experimental data showed that the incipient mean flow velocities of bivalve shells in the convex upward position were about 1.4–2.8 times larger than those in the convex downward position. The incipient mean velocity data were regressed to obtain the motion threshold equations applicable to bivalve shells in the convex upward and convex downward positions as well as gastropod shells under different final orientations. [ABSTRACT FROM AUTHOR]

Sessile benthic organisms like oysters inhabit the intertidal zone, subject to alternating hypoxia and reoxygenation (H/R) episodes during tidal movements, impacting respiratory chain activities and metabolome compositions. We investigated the effects of constant severe hypoxia (90 min at ~ 0% O2) followed by 10 min reoxygenation, and cyclic hypoxia (5 cycles of 15 min at ~ 0% O2 and 10 min reoxygenation) on isolated mitochondria from the gill and the digestive gland of Crassostrea gigas respiring on pyruvate, palmitate, or succinate. Constant hypoxia suppressed oxidative phosphorylation (OXPHOS), particularly during Complex I-linked substrates oxidation. It had no effect on mitochondrial reactive oxygen species (ROS) efflux but increased fractional electron leak (FEL). In mitochondria oxidizing Complex I substrates, exposure to cyclic hypoxia prompted a significant drop after the first H/R cycle. In contrast, succinate-driven respiration only showed significant decline after the third to fifth H/R cycle. ROS efflux saw little change during cyclic hypoxia regardless of the oxidized substrate, but Complex I-driven FEL tended to increase with each subsequent H/R cycle. These observations suggest that succinate may serve as a beneficial stress fuel under H/R conditions, aiding in the post-hypoxic recovery of oysters by reducing oxidative stress and facilitating rapid ATP re-synthesis. The impacts of constant and cyclic hypoxia of similar duration on mitochondrial respiration and oxidative lesions in the proteins were comparable indicating that the mitochondrial damage is mostly determined by the lack of oxygen and mitochondrial depolarization. The ROS efflux in the mitochondria of oysters was minimally affected by oxygen fluctuations indicating that tight regulation of ROS production may contribute to robust mitochondrial phenotype of oysters and protect against H/R induced stress. [ABSTRACT FROM AUTHOR]

Mussel periostracum, a nonliving multifunctional gel that covers the rigid inorganic shells of mussels, provides protection against mechanical impacts, biofouling, and corrosion in harsh ocean environments. The inner part of the periostracum, which emerges from biological tissues, functions as a natural interface between tissue and inorganic materials. The periostracum shows significant potential for application in implantable devices that provide interfaces; however, this system remains unexplored. In this study, we revealed that the inner periostracum performs graded mechanical functions and efficiently dissipates energy to accommodate differences in stiffness and stress types on both sides. On the tissue end, the lightly pigmented periostracum exhibits extensibility and energy dissipation under repetitive tension. This process was facilitated by the slipping and reassembly of β-strands in the discovered major proteins, which we named periostracin proteins. On the shell end, the highly pigmented, mineralized, and porous segment of the periostracum provided stiffness and cushioned against compressive stresses exerted by the shell valves during closure. These findings offer a novel possibilities for the design of interfaces that bridge human tissue and devices. The interfaces linking biological tissues and man-made devices is challenging due to mechanical mismatch, biofouling, and water content. Soft materials such as hydrogels have emerged in diverse applications, however, their unresolved problem is the loss of functions in a short period. This report explores natural connective tissue, called periostracum, which is perfectly bridged between biological tissue and inorganic nonliving shell with high durability for long-lasting functions. Its hierarchically designed strategy provides a novel blueprint to design durable soft materials for the interfacing device into tissue. [ABSTRACT FROM AUTHOR]

Research on the microbiota associated with marine invertebrates is important for understanding host physiology and the relationship between the host and the environment. In this study, the microbiota of the green mussel Perna viridis was characterized at the tissue scale using 16S rRNA gene high-throughput sequencing and compared with the microbiota of the surrounding environment. Different mussel tissues were sampled, along with two environmental samples (the mussel's attachment substratum and seawater). The results showed that the phyla Proteobacteria, Bacteroidetes, and Spirochaetae were dominant in mussel tissues. The bacterial community composition at the family level varied among the tissues of P. viridis. Although the microbiota of P. viridis clearly differed from that of the surrounding seawater, the composition and diversity of the microbial community of the foot and outer shell surface were similar to those of the substratum, indicating their close relationship with the substratum. KEGG prediction analysis indicated that the bacteria harbored by P. viridis were enriched in the degradation of aromatic compounds, osmoregulation, and carbohydrate oxidation and fermentation, processes that may be important in P. viridis physiology. Our study provides new insights into the tissue-scale characteristics of mussel microbiomes and the intricate connection between mussels and their environment. [ABSTRACT FROM AUTHOR]

The object of the study is to determine the critical impact speed during shell destruction, study crack formation in the shell, and grind the shell. When operating a grinder-mixer-dryer, problems arise such as determining the speed of impact on the shell depending on the height of its fall, the lack of ability to determine the speed of shell fall from certain heights, which complicates planning the operation of the finger shaft. As a result of research, it was found that an auger with knives crushes and moves feed raw materials, and the impact-spreading shaft ensures partial grinding of fragile raw materials and intensive processes of mixing and drying wet feed with uniform filling of the installation hopper. The appearance of cracks on the shell when it falls from a height of 0.15 m has been experimentally recorded. Therefore, this speed of impact of the shell on a metal surface is the critical peripheral speed of the impact-spreading shaft, which ensures partial crushing of the shell. As a result of theoretical studies, an analytical expression was obtained that provides the determination of the shell impact speed depending on the height of its fall. The value of the critical peripheral speed of the fingers of the impact-spreading shaft is determined to be 1.66 m/s. The experimental results showed the effective occurrence of grinding, mixing and drying processes. Moreover, within 15 minutes of operation of the installation, the wet shell was crushed in accordance with the requirements. The uniformity reached up to 90 % within 4 to 6 minutes of its operation, and drying proceeded at a rate of 26.54 % per hour. All this proves the effectiveness of the processes of grinding, mixing and drying wet food, and also confirms the reliability of theoretical research [ABSTRACT FROM AUTHOR]

The frequency and severity of marine heatwaves (MHWs) have reached new heights in the last two decades. Intensifying MHWs can affect intertidal bivalves, but the extent of their impacts remains largely underestimated. Here, we tested how persistent (P-MHW) and repeated (R-MHW) MHWs events affected the physiological energetics of ecologically and economically clams Mercenaria mercenaria inhabiting intertidal habitats. Compared to individuals maintained under ambient conditions, the clams exposed to both two scenarios of MHWs exhibited significant increases in their clearance rate, absorption efficiency, respiration rate, excretion rate, and scope for growth, showing compensatory energetic mechanisms to cope with MHWs. Especially, physiological energetics of M. mercenaria were more sensitive to repeated than persistent scenarios of MHWs. Given that the physiological response can act as an early and sensitive indicator of the fitness of intertidal bivalves, our results indicated that M. merceneria can likely hold the ability to readily recover from repeated to persistent exposure MHWs, enabling its continued resilience in a rapidly changing marine environment. [ABSTRACT FROM AUTHOR]

Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon (PAH) with the most carcinogenic effects of all the PAHs, has multiple toxic effects on marine bivalves. We investigated the interference mechanism of B[a]P on food metabolism (sugars, proteins, and sugars), and on reproductive endocrine and ovarian development in female scallops (Chlamys farreri). Scallops were exposed to different concentrations of B[a]P concentrations of 0, 0.38, 3.8, and 38 μg/L throughout gonadal development. Total cholesterol and triglyceride contents in the digestive glands were increased, and their synthesis genes were upregulated. The plasma glucose contents decreased with the inhibition of glycogen synthesis genes and the induction of glycolysis genes in the digestive gland. The results showed that B[a]P had endocrine‐disrupting effects on scallops, that it negatively affected genes related to ovarian cell proliferation, sex differentiation, and egg development, and that it caused damage to ovarian tissue. Our findings supplement the information on B[a]P disruption in gonadal development of marine bivalves. Environ Toxicol Chem 2024;43:748–761. © 2023 SETAC [ABSTRACT FROM AUTHOR]

The shell of bivalves acts as structural support, defence against predators, stressors, and maintenance of homeostasis. Haemocytes and mantle epithelial cells participate in shell formation. Mantle epithelial cells produce the organic matrix of the shell and are associated with biomineralization because of their proximity to the shell surface and ability to maintain shell deposition ex vivo. Haemocytes play an immunological role and are involved in Ca2+ and CO32- intracellular transport implicated in shell mineralization. This study aims to evaluate the expression of molecules that play key roles in internal defence and the nervous system, in epithelial cells and haemocytes of the outer mantle margin of two species of bivalves, Polititapes aureus Gmelin, 1791 and Cerastoderma glaucum Bruguière, 1789, to highlight their collaborative role in shell formation. Our data show for the first time the presence of serotonin/S100 protein, and TLR2/iNOS colocalization in the haemocytes and mantle epithelial cells of P. aureus and C. glaucum , suggesting that the mantle cells perform their canonical role of sensory and biomineralizing activity, while the haemocytes perform their typical immune function, and their collaboration in shell formation, providing new information on cellular interactions in shell formation and giving more details for taxonomical studies. [ABSTRACT FROM AUTHOR]

The chemical structure of Ostrea edulis (O. edulis) shells was investigated in this work. The study determined zero charge points (PZC) of Ostrea edulis shells. The shell surface charge status is indicated by the PZC value. It was found that the shell PZC value was 8.30. The shells were subjected to Energy Dispersive X-Ray Spectroscopy (EDS) analyses and scanning electron microscope (SEM) pictures. The main structure of calcium carbonate (CaCO3) is made up of carbon, oxygen, and calcium atoms, which were found in the largest quantities based on the EDS data. The structure of CaCO3 was supported by Fourier Transform Infrared Spectroscopy (FT-IR) analysis. As part of the study, X-Ray Diffraction (XRD) investigations were conducted, and it was found that the shell structures are primarily composed of an aragonite and CaCO3 mixture. As is well known, CaCO3, which makes up roughly 94% of the shell, is the primary constituent of bivalves' shells. This research offers a thorough examination of the chemical makeup of O. edulis shells. This study is thought to serve as the foundation for further research on the biological and chemical characteristics of marine species. [ABSTRACT FROM AUTHOR]

The Circular Economy emerges as an alternative to reinvent the linear production model (take–make–waste), focusing on reintegrating waste into the production cycle, and aiming to minimize both environmental disposal and the unrestrained extraction of raw materials. In this context, the concept of Blue Economy arises, an approach centered on preserving and valorizing marine and coastal resources. This article aims to develop a model for the circuit of bivalve shells, emphasizing the transformation of the residues into new products and identifying how these processes affect sociocultural, economic, and environmental dimensions. The methodology involved the surveying of local stakeholders directly involved in bivalve production and consumption to identify the relationship of these stakeholders with the production, marketing, and disposal of bivalves. It is concluded that biowaste has potential, and there is interest among local stakeholders in reusing it, but a lack of knowledge and connection among stakeholders ultimately leads to the devaluation of the product. The circuit of bivalves is necessary to identify value, propose correct collection, and stimulate interest in their reuse, both by other industries and by the aquaculture industry itself. Exploring the potential for reusing bivalves and mitigating their waste, as well as preventing improper disposal, could drive the development of the Blue Circular Economy in coastal regions. [ABSTRACT FROM AUTHOR]

Blastocystis sp. is the most common single-celled eukaryote colonizing the human gastrointestinal tract worldwide. Because of the proven zoonotic potential of this protozoan, sustained research is therefore focused on identifying various reservoirs of transmission to humans, and in particular animal sources. Numerous groups of animals are considered to be such reservoirs due to their handling or consumption. However, some of them, including mollusks, remain underexplored. Therefore, a molecular epidemiological survey conducted in wild mussels was carried out in Northern France (Hauts-de-France region) to evaluate the frequency and subtypes (STs) distribution of Blastocystis sp. in these bivalve mollusks. For this purpose, 100 mussels (Mytilus edulis) were randomly collected in two sampling sites (Wimereux and Dannes) located in the vicinity of Boulogne-sur-Mer. The gills and gastrointestinal tract of each mussel were screened for the presence of Blastocystis sp. by real-time polymerase chain reaction (qPCR) assay followed by direct sequencing of positive PCR products and subtyping through phylogenetic analysis. In parallel, sequences of potential representative Blastocystis sp. isolates that were previously obtained from temporal surveys of seawater samples at marine stations offshore of Wimereux were integrated in the present analysis. By taking into account the qPCR results from all mussels, the overall prevalence of the parasite was shown to reach 62.0%. In total, more than 55% of the positive samples presented mixed infections. In the remaining mussel samples with a single sequence, various STs including ST3, ST7, ST14, ST23, ST26 and ST44 were reported with varying frequencies. Such distribution of STs coupled with the absence of a predominant ST specific to these bivalves strongly suggested that mussels might not be natural hosts of Blastocystis sp. and might rather be carriers of parasite isolates from both human and animal (bovid and birds) waste. These data from mussels together with the molecular identification of isolates from marine stations were subsequently discussed along with the local geographical context in order to clarify the circulation of this protozoan in this area. The identification of human and animal STs of Blastocystis sp. in mussels emphasized the active circulation of this protozoan in mollusks and suggested a significant environmental contamination of fecal origin. This study has provided new insights into the host/carrier range and transmission of Blastocystis sp. and emphasized its potential as an effective sentinel species for water quality and environmental contamination. [ABSTRACT FROM AUTHOR]

The giant clam shells are considered excellent marine bioarchives and have been used in studying current and past climate variabilities. Here, we present the microstructure and growth rate variability of a giant clam shell (T. maxima) collected from the Minicoy Island Lakshadweep, India. We employed FE-SEM, EDX, Raman spectroscopy and petrographic analysis to identify coherent records of the past marine environmental settings and factors controlling growth rates in T. maxima. A consistent growth rate was observed throughout the shell ontology, except for the year 2010, when a relatively slow growth rate was observed due to exceptionally warm water temperatures. Slower microstructural growth is confirmed by an anomalously negative excursion in δ18O values caused by an anomalous sea surface warming event. Such kind of warming was previously documented for the region in 2010 that caused widespread coral bleaching throughout the Lakshadweep Archipelago. Interestingly, our results do not reveal any major growth hiatus in the T. maxima even after experiencing this anomalous thermal stress event, demonstrating the ability of these bivalve shells to reliably reconstruct past environments. These findings advance the potential of combining data from shell microstructure, petrographic, and isotope (δ18Oshell) analyses, to reconstruct the past extreme events preserved in giant clam shells from the Lakshadweep Archipelago. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT) is a clinically approved treatment for tumors, and it relies on the phototoxicity of photosensitizers by producing reactive oxygen species (ROS) to destroy cancer cells under light irradiation. However, such phototoxicity is a double-edged sword, which is also harmful to normal tissues. To manipulate phototoxicity and improve the therapy effect, herein we have proposed a dressing-undressing strategy for de-activating and re-activating therapy functions of photosensitizer nanoparticles. One kind of metal organic framework (PCN-224), which is composed of Zr(IV) cation and tetrakis (4-carboxyphenyl) porphyrin (TCPP), has been prepared as a model of photosensitizer, and it has size of ∼70 nm. These PCN-224 nanoparticles are subsequently coated with a mesoporous organic silica (MOS) shell containing tetrasulfide bonds (-S-S-S-S-), realizing the dressing of PCN-224. MOS shell has the thickness of ∼20 nm and thus can block 1O 2 (diffusion distance: <10 nm), deactivating the phototoxicity and preventing the damage to skin and eyes. Furthermore, PCN-224@MOS can be used to load chemotherapy drug (DOX·HCl). When PCN-224@MOS-DOX are mixed with glutathione (GSH), MOS shell with -S-S-S-S- bonds can be reduced by GSH and then be decomposed, which results in the undressing and then confers the exposure of PCN-224 with good PDT function as well as the release of DOX. When PCN-224@MOS-DOX dispersion is injected into the mice and accumulated in the tumor, endogenous GSH also confers the undressing of PCN-224@MOS-DOX, realizing the in-situ activation of PDT and chemotherapy for tumor. Therefore, the present study not only demonstrates a general dressing-undressing strategy for manipulating phototoxicity of photosensitizers, but also provide some insights for precise therapy of tumors without side-effects. Photosensitizers can generate reactive oxygen species (ROS) under light radiation to destroy cancer cells. However, this phototoxicity is a double-edged sword and also harmful to normal tissues such as the skin and eyes. To control phototoxicity and improve therapeutic efficacy, we prepared a PCN-224@MOS-DOX nanoplatform and proposed a dressing and undressing strategy to deactivate and reactivate the therapeutic function of the photosensitizer nanoparticles. The MOS shell can block the diffusion of 1O 2 , eliminate phototoxicity, and prevent damage to the skin and eyes. When injected into mice and accumulated in tumors, PCN-224@MOS-DOX dispersions are endowed with an endogenous GSH-driven undressing effect, achieving in situ activation of PDT and tumor chemotherapy. [Display omitted] [ABSTRACT FROM AUTHOR]

Hong Kong oysters (Crassostrea hongkongensis) are an important marine bivalve with nutritional and commercial value. The expanded off-bottom farming scale in recent years makes the oysters more susceptible to exposure to abiotic stresses, such as salinity stress, an important environmental factor that has been proven to have significant effects on oyster growth and development. However, the molecular mechanism is still unclear. Cyclin E is an important protein in the process of cell cycle regulation that is indispensable for propelling G1/S phase transition in a dose-dependent manner. In order to investigate whether the salinity stress affects cyclin E expression in oysters, the cDNA sequence of C. hongkongensis cyclin E (Ch-CCNE) was isolated from a gill cDNA library, and the 2.8 kbp length cDNA fragment contained a complete open reading frame (ORF) encoding 440 amino acid residues. Ch-CCNE mRNA was highly expressed in the gonad and low in the adductor mussel, mantle, gill, labial palp, and digestive gland. The recombinant CCNE protein was expressed and purified in a pET32a(+)-CCNE/Escherichia coli BL21(DE3) system via IPTG induction and was used for generating mice anti-Ch-CCNE antiserums. Western blot analysis showed that the CCNE protein in the gill was maintained at low expression levels under either hypo- (5 ppt) or hyper- (35 ppt) salinity, and could be produced at high levels under appropriate salinity during a 10-day exposure period. The immuno-localization indicated that the Ch-CCNE protein was distributed in the nucleus. These results suggested that either hypo- or hyper-salinity stress could inhibit the CCNE expression of Hong Kong oysters and their negative impact on cell division and proliferation. [ABSTRACT FROM AUTHOR]

The isotope ratios of zinc (66Zn/64Zn expressed as δ66Zn), a vital nutrient, increasingly demonstrate trophic discrimination among vertebrates, making δ66Zn a valuable dietary proxy for ecological, archaeological, and palaeontological studies. Given the novelty of the methodology, tissue-diet and tissue-tissue zinc isotope fractionation factors remain poorly understood and have so far only been studied in a few terrestrial mammals. Here, we investigate δ66Zn compositions of enameloid, bone, and white muscle of seven artificially-fed pisciculture gilt-head seabreams (Sparus aurata) from offshore Israel, in comparison to the Zn isotope composition of their diet. In addition, we also analysed δ66Zn values in the same tissues of wild-caught S. aurata, bluespotted seabream (Pagrus caeruleostictus) and grey triggerfish (Balistes capriscus) caught off the coast of Israel. We determine a tissue-diet δ66Zn offset for Sparus aurata of − 0.04 ± 0.09 ‰ (2SD) for bone, − 0.29 ± 0.06 ‰ (2SD) for enameloid, and − 0.45 ± 0.07 ‰ (2SD) for white muscle. Wild-caught fish have much higher among-individual δ66Zn variability with values distinct from the pisciculture S. aurata, documenting a much more isotopically heterogeneous diet consumed by the wild individuals. Still, tissue–tissue δ66Zn differences in wild-caught individuals are close to those observed in the pisciculture ones with progressively lower δ66Zn values in the order bone > enameloid > white muscle. Our results demonstrate predictable tissue-diet and tissue-tissue δ66Zn differences among fish hard and soft tissues and can be applied to identify the δ66Zn values of dietary input, thereby informing trophic (palaeo)ecological reconstructions. [ABSTRACT FROM AUTHOR]

From mathematical models of growth to computer simulations of pigmentation, the study of shell formation has given rise to an abundant number of models, working at various scales. Yet, attempts to combine those models have remained sparse, due to the challenge of combining categorically different approaches. In this paper, we propose a framework to streamline the process of combining the molecular and tissue scales of shell formation. We choose these levels as a proxy to link the genotype level, which is better described by molecular models, and the phenotype level, which is better described by tissue-level mechanics. We also show how to connect observations on shell populations to the approach, resulting in collections of molecular parameters that may be associated with different populations of real shell specimens. The approach is as follows: we use a Quality-Diversity algorithm, a type of black-box optimization algorithm, to explore the range of concentration profiles emerging as solutions of a molecular model, and that define growth patterns for the mechanical model. At the same time, the mechanical model is simulated over a wide range of growth patterns, resulting in a variety of spine shapes. While time-consuming, these steps only need to be performed once and then function as look-up tables. Actual pictures of shell spines can then be matched against the list of existing spine shapes, yielding a potential growth pattern which, in turn, gives us matching molecular parameters. The framework is modular, such that models can be easily swapped without changing the overall working of the method. As a demonstration of the approach, we solve specific molecular and mechanical models, adapted from available theoretical studies on molluscan shells, and apply the multiscale framework to evaluate the characteristics of spines from three distinct populations of Turbo sazae. Author summary: Connecting genotype to phenotype is a fundamental goal in developmental biology. While many studies examine this link in model organisms for which gene regulatory networks are well known, for non-model organisms, different techniques are required, and multiscale computational modeling offers a promising direction. In this paper, we develop a framework linking molecular-scale interactions to tissue-level growth and mechanics to organ-level characteristics in order to investigate spine formation in T. sazae, a species of mollusc that displays remarkable phenotypic plasticity in spine form. Our analysis uncovers a subtle but statistically significant difference in spine form between shell specimens collected from three different localities in Japan. Moreover, by tracing the difference in form through parametric differences in the multiscale framework, we provide mechanistic insight as to how environmental differences may translate to a change in form. The methodology we present may readily be extended to more detailed modeling of this system, and the conceptual framework is amenable for multiscale analysis in other systems. [ABSTRACT FROM AUTHOR]

Freshwater river mouths may facilitate cross‐habitat resource use and bidirectional subsidization through (a) active cross‐habitat movement by consumers like fish and (b) water and material movement both downstream, from tributary to nearshore lake, and in the opposite direction due to backflow processes. Despite potential importance of freshwater river mouths, relative contributions of lentic and tributary energy sources to fishes along these ecotones remain understudied, in part because measuring cross‐habitat subsidization is not straightforward. We assessed cross‐habitat subsidization of three fish consumers round goby (Neogobius malanostomus), yellow perch (Perca flavescens), and alewife (Alosa psuedoharengus) in three river mouths of Lake Michigan, USA. Specifically, we (a) measured stable isotope ratios (δ13C, δ15N, δ2H, δ18O) in ambient water, bivalve shells, potential invertebrate prey, and fish soft tissue, and we assessed fish nutritional status based on essential fatty acid composition, and (b) estimated Bayesian ellipses and mixing models including either two (δ13C‐δ15N) or three (δ13C‐δ15N‐δ2H) isotope ratios. Results revealed evidence of bidirectional habitat subsidies for all fishes, but energy subsidies varied by species and across river mouths; likely related to differences in species‐specific behavior and hydrologic differences among river mouths. Relative to nearshore oligotrophic Lake Michigan, fish in productive tributary environments contained relatively low essential fatty acid content, suggesting a possible trade‐off between prey quantity and quality across habitats. This study advances our understanding of resource connectivity in lake ecosystems and the combined use of multiple stable isotopes (including mixing models) and fatty acids to document cross‐habitat subsidies along freshwater ecotones. [ABSTRACT FROM AUTHOR]

Objective: Using bivalves to indicate aquatic pollutants was favorable for discerning the negative effects of high levels of metal accumulation in tissue. We investigated the correlation between trace metal accumulation and the tissue oxidative response of two bivalves. Methods: The Asian green mussel Perna viridis and the blood cockle Tegillarca granosa were sampled along with seawater and sediments from three locations around Pattani Bay, Thailand. Accumulation of nine trace metals (cadmium, cobalt, copper, chromium, nickel, manganese, iron, zinc, and lead) in seawater, sediments, and tissue and the oxidative tissue response were evaluated. Metal bioaccumulation factor, biota–sediment accumulation factor, and histopathology were also indicated. Result: The present study found that P. viridis and T. granosa were macroconcentrators and bioaccumulative of cadmium, and their tissue accumulation of cadmium was strongly related to lipid peroxidation activation. Perna viridis exhibited a higher oxidative response than T. granosa, as indicated by malondialdehyde, catalase, and reduced glutathione levels. Conclusion: The present study indicated that P. viridis and T. granosa were macroconcentrators and bioaccumulative of cadmium, and their tissue accumulation of cadmium was strongly related to lipid peroxidation activation. Research has shown discernible negative effects of a high level of metal accumulation in tissue, and deformed and damaged tissues were present in the gills, digestive glands, intestines, and feet of P. viridis and T. granosa. Impact statementBivalves' structural and physiological alterations are associated with trace metal accumulation in their tissue. Tissue accumulation of cadmium has an outstanding impact on a bivalve's tissue stress and response, which influences the organisms' health, though bivalves have a high ability to accumulate and concentrate pollutants in their tissues. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) persistently pollute marine ecosystems even though their production has been discontinued decades ago. Deep-sea organisms have been shown to accumulate PCBs and other persistent organic compounds; however, the extent of contamination and its effects remain poorly understood. Here, we measured PCB concentrations in separated organs of non-feeding bivalve clams belonging to Phreagena, a taxon representative of deep-sea chemosynthetic ecosystems. The highest concentrations of PCBs were detected in the ovaries. We also examined surface sediments of the clam habitat and observed concentrations comparable to those in the sediments of the seas around Japan, including shallow waters. The results showed that PCBs from the environment penetrate Phreagena clams through the body surface and accumulate in the female reproductive system. This raises concerns about a potentially severe direct impact on the survival of vulnerable and highly endemic deep-sea chemosynthetic bivalves. [ABSTRACT FROM AUTHOR]

Acanthocephalans are dioecious parasites that gain sexual maturity in the alimentary canal of their definitive hosts (gnathostome vertebrates). This initial survey by light and transmission electron microscopy was conducted on the functional organization of the ovarian balls and uterine bell in mature females and on Saefftigen's pouch and the copulatory bursa in males. We studied these structures via the example of Centrorhynchus globocaudatus (Palaeacanthocephala) in Falco tinnunculus and Buteo buteo, from the Province of Ferrara (Northern Italy). Our study confirms that the ovarian balls have surface microvilli and consist of a multinucleate supporting syncytium and a cellular region with oogonial syncytium, single germ cells, zygotes, and shelled eggs. Germ cells are embedded in the supporting syncytium. The ultrastructural features of these components and data on fertilization, shell formation, and release from the ovarian ball, alongside insights into the likely egg sorting function of the uterine bell, are provided. We also present light and electron microscopy observations of Saefftigen's pouch and a suggestion regarding its hydrostatic functioning in the eversion of the copulatory bursa. [ABSTRACT FROM AUTHOR]

Simple Summary: The innate immunity of marine bivalves is challenged upon exposure to heat stress, but there is limited knowledge of its molecular mechanism. In this study, genes in the TLR4-MyD88 signaling pathway were investigated in a new scallop strain: "Hongmo No. 1" (Bohai Red ♂ × A. irradians concentricus ♀). This is the first study reporting that acute heat stress obviously inhibited the TLR4-MyD88 signaling pathway of bivalves, even with LPS stimulation. The subsequent RNAi targeting TLR4 gene in the new scallop strain "Hongmo No. 1" indicated the key role of TLR4-MyD88 signal transduction in the immune response. Acute heat stress seemed to affect the response of downstream mediator molecules to the inhibition of HMTLR4. These results provide more information about bivalve immunity under heat stress, which is expected to improve heat tolerance to cope with more frequent and extreme heat wave events. The innate immunity of marine bivalves is challenged upon exposure to heat stress, especially with increases in the frequency and intensity of heat waves. TLR4 serves a classical pattern recognition receptor in recognizing pathogenic microorganisms and activating immune responses. In this study, three genes, HMTLR4, HMMyD88 and HMTRAF6, were characterized as homologs of genes in the TLR4-MyD88 signaling pathway in the selected scallop strain "Hongmo No. 1". According to RT-PCR, acute heat stress (32 °C) inhibited genes in the TLR4-MyD88 signaling pathway, and LPS stimulation-induced activation of TLR4-MyD88 signal transduction was also negatively affected at 32 °C. ELISA showed LPS-induced tumor necrosis factor alpha (TNF-α) or lysozyme (LZM) activity, but this was independent of temperature. RNA interference (RNAi) confirmed that HMTLR4 silencing suppressed the expression of its downstream gene, whether at 24 °C or at 32 °C. The level of TNF-α and the activity of LZM also decreased after injection with dsRNA, indicating a negative effect on the innate immunity of scallops. Additionally, acute heat stress affected the suppression of downstream gene expression when compared with that at 24 °C, which led us to the hypothesis that heat stress directly influences the downstream targets of HMTLR4. These results enrich the knowledge of scallop immunity under heat stress and can be beneficial for the genetic improvement of new scallop strains with higher thermotolerance. [ABSTRACT FROM AUTHOR]

The traditional walnut shelling methods, involving single‐stage or secondary processes, face challenges such as increased costs, uncertainties in shell positioning, and irregular crack expansion. To address these issues, this article introduces an innovative pneumatic impact‐twisting combined shelling method based on walnut fixed posture. The shelling mechanism design and orthogonal test were conducted, optimizing parameters like spring wire diameter (A), pressing head rotation angle (B), and cylinder locking air pressure (C) using evaluation criteria such as superior‐grade rate, intermediate‐grade rate, broken kernel rate, and shelling rate. Results indicate that the optimal shelling effect is achieved with a 3.5 mm steel spring wire diameter, a 100° downward pressing head rotation angle, and a 0.6 MPa cylinder locking air pressure on the pressure arm. The corresponding rates are as follows: superior‐grade rate 29.49%, intermediate‐grade rate 52.54%, broken kernel rate 10.14%, and shelling rate 91.04%. This study demonstrates that the pneumatic impact‐twisting combined walnut fixed posture shelling method improves post‐shelling quality, offering new design concepts for walnut shelling equipment. Practical Applications: This introduces an innovative method that combines impact with twisting, and a pneumatic impact‐twisting combined walnut fixed posture shell‐breaking test device has been developed. Mechanical analysis was conducted for each stage of shell‐breaking. The research indicates that the pneumatic impact‐twisting combined method can enhance the production quality of walnut kernels after shell‐breaking. The test results indicate an improvement in the yield of 1/2 and 1/4 kernels compared to existing shell‐breaking methods. The inventive design of this shell‐breaking module contributes to the walnut kernel quality in the shell‐breaking production line, offering new methods and concepts for the design and advancement of walnut shell‐breaking devices. [ABSTRACT FROM AUTHOR]

This paper studies the composition and properties of shells of bivalve mollusks (Crenomytilus grayanus, Callista brevisiphonata, and Mizuhopecten yessoensis) from coastal discharges with a view to the possibility of their use in photocatalytic water treatment systems. The clam shells are considered in terms of application in the form of a powder material as a precursor for creating photocatalysts, and also as a carrier of photocatalytic coatings. It was shown that the main phase composing the shell material was calcium carbonate in two crystallographic modifications—calcite and aragonite. The presence of inorganic impurities in all studied clam shells did not exceed one mass percent. The main share was made up of elements included in the composition of calcium carbonate, which confirmed the high bio-indifference of the materials under study. Depending on the physiological and environmental features of the structure of clam shells, different contents of the organic component in their composition were observed. The granulometric characteristics of crushed clam shells (average diameter, specific surface area, and distribution modality) were studied. It was shown that the maximum values of bending strength of 5 MPa and compressive strength of 2 MPa are characterized by Mizuhopecten yessoensis shells with the lowest porosity of 2.91%. The features of sorption and photosorption processes of both whole and crushed shells in relation to four organic dyes at different temperatures and degrees of illumination were studied. Based on crushed shells of Mizuhopecten Yessoensis and titanium dioxide, functional materials (CaxTiyOz) were obtained, and their morphology and photocatalytic properties were studied. An example of the practical use of clam shells as a carrier of a photocatalytic coating is given. [ABSTRACT FROM AUTHOR]

Diverse, abundant and well-preserved mollusk fauna are here reported for the first time from the eastern coast Makram area, where Upper Miocene (Tortonian) sediments of the Dar Pahn Unit crop out, representing shoreface tidal influenced deposits composed mainly of ligh-gray marls. Multiple articulated bivalves and completely preserved the gastropod and bivalve shells indicate little or no transport at all from the original habitat of the mollusk assemblage. A total of 313 specimens, from which 271 correspond to gastropods, were identified only at generic level, since the purpose of this contribution is to offer an introduction to this exceptionally well-preserved mollusk assemblage. Previous studies of the area include detailed nannoplankton biostratigraphy and the report of a balaenopterid cetacean. Future studies include the detailed identification of the specimens, along with sediment analysis in order to find protoconchs and offer an extended version of this introductory report. [ABSTRACT FROM AUTHOR]

Given the limited understanding of benthic fauna along the Algerian coast, this study was conducted to explore the diversity of bivalve mollusks specifically on the Algerian west coast. The primary objectives of this study were to create a comprehensive but not exhaustive inventory of bivalve species in this region and to analyze the distribution of these species within the study areas and neighboring regions. The research involved the investigation of numerous sandy beaches across four sectors of the Algerian west coast: Tlemcen, Béni-Saf, Ain-Temouchent, and Oran. Between June 2019 and April 2020, a random collection of empty bivalve shells was carried out in the foreshore zones of 16 beaches within these sectors. This extensive collection of 10,076 shells resulted in the identification of 56 bivalve mollusk species, categorized into 22 families. Among these families, the most prominent were Cardiidae, Donacidae, Glycymerididae, and Veneridae, serving as the most representative families across all four sectors. Notably, the Glycymerididae family was the most abundant along the Oran coast, with nearly 2,000 individuals, although they were less prevalent on the beaches of the Béni Saf sector. In contrast, the Veneridae family was prevalent on the beaches of the Tlemcen, Béni Saf, and Aïn-Témouchent sectors. Within the Veneridae family, there was remarkable diversity, featuring 11 species, followed by the Cardiidae family with 6 species, and the Limidae and Pectinidae families with 5 species each. Finally, among the identified species, the most abundant ones included Acanthocardia tuberculata (Linnaeus, 1758), Chamelea gallina (Linnaeus, 1758), Glycymeris nummaria (Linnaeus, 1758), and Donax trunculus (Linnaeus, 1758), each belonging to the Cardiidae, Veneridae, Glycymerididae, and Donacidae families, respectively. [ABSTRACT FROM AUTHOR]

The development of larvae and the growth and feeding of juveniles of the veined rapa whelk Rapana venosa, an invader in the Black Sea, has been studied in experimental conditions. With a balanced diet consisting of six microalgal species and at a water temperature of 22−23°C, the planktonic life of this gastropod lasted 22 days. The metamorphosis finished when the individuals changed their feeding behavior for the predatory type on the 25th day after the larvae emerged from the egg capsules. Cases of cannibalism have been recorded among the young individuals. The size of juvenile individuals capable of perforating bivalve shells has been clarified. One to five holes of various shapes per mussel shell could be observed. Rapa whelks bored through the thin edge of a mussel shell most often with a hole projection onto the mantle edge and most rarely with a projection onto the anterior contractile muscles of the foot. The study of the perforated holes using scanning electron microscopy has shown that individuals with a size of 20−25 mm bore mussel shells with the radula and dissolve the walls with a secretion produced by the accessory boring organ (ABO). Correlations of the mass and size values (Wtot = 0.002H2.9377, R2 = 0.9769), feeding rate (P = 0.64H2.8769, R2 = 0.9699), and perforation diameters (d = 170.78e0.1029H, R2 = 0.9403) with the gastropod shell height have been established in mussel spat shells. [ABSTRACT FROM AUTHOR]

Background: Changshun green-shell laying hens are unique to the Guizhou Province, China, and have high egg quality but relatively low yield. Egg production traits are regulated by the hypothalamus-pituitary-ovary axis. However, the underlying mechanism remains unclear. Thus, we conducted RNA sequencing of hypothalamic and pituitary tissues from low- and high-yielding Changshun green-shell laying hens to identify critical pathways and candidate genes involved in controlling the egg production rate. Results: More than 39 million clean reads per sample were obtained, and more than 82% were mapped to the Gallus gallus genome. Further analysis identified 1,817 and 1,171 differentially expressed genes (DEGs) in the hypothalamus and pituitary, respectively. Nineteen DEGs were upregulated in both the hypothalamus and pituitary of high-yielding chickens. The functions of these DEGs were mainly associated with ion transport or signal transduction. Gene set enrichment analysis revealed that the pathways enriched in the hypothalamus were mainly associated with gonadotropin-releasing hormone (GnRH) secretion, neurotransmitter release, and circadian rhythms. The pathways enriched in the pituitary were mainly associated with GnRH secretion, energy metabolism, and signal transduction. Five and four DEGs in the hypothalamus and pituitary, respectively, were selected randomly for qRT-PCR analysis. The expression trends determined via qRT-PCR were consistent with the RNA-seq results. Conclusions: The current study identified 19 DEGs upregulated in both the hypothalamus and pituitary gland, which could provide an important reference for further studies on the molecular mechanisms underlying egg production in Changshun green-shell laying hens. In addition, enrichment analysis showed that GnRH secretion and signal transduction, especially neurotransmitter release, play crucial roles in the regulation of egg production. [ABSTRACT FROM AUTHOR]

The spread of oxygen deficiency in nearshore coastal habitats endangers benthic communities. To better understand the mechanisms leading to oxygen depletion and eventually hypoxia, predict the future development of affected ecosystems, and define suitable mitigation strategies requires detailed knowledge of the dissolved oxygen (DO) history. Suitable high-resolution DO archives covering coherent time intervals of decades to centuries include bivalve shells. Here, we explored if the microstructure, specifically disturbance lines, in shells of Arctica islandica from the Baltic Sea can be used as an alternative or complementary proxy to Mn/Cashell to track the frequency and severity of past low-DO events. Disturbance lines differ from periodic annual growth lines by the presence of fine complex crossed lamellae instead of irregular simple prisms. Aside from a qualitative assessment of microstructural changes, the morphology of individual biomineral units (BMUs) was quantitatively determined by artificial intelligence-assisted image analysis to derive models for DO reconstruction. As demonstrated, Mn-rich disturbance lines can provide a proxy for past deoxygenation events (i.e., DO < 45 µmol/L), but it currently remains unresolved if low DO leads to microstructurally distinct features that differ from those caused by other environmental stressors. At least in studied specimens from the Baltic Sea and Iceland, low temperature, salinity near the lower physiological tolerance, or food scarcity did not result in disturbance lines. With decreasing DO supply, disturbance lines seem to become more prominent, contain more Mn, and consist of increasingly smaller and more elongated BMUs with a larger perimeter-to-area ratio. Although the relationship between DO and BMU size or elongation was statistically significant, the explained variability (<1.5%) was too small and the error too large to reconstruct DO values. BMU parameters may reveal a closer relationship with DO if studied in three dimensions and if the DO content was determined at high resolution, directly at the position where the bivalves lived, something that future work should address. [ABSTRACT FROM AUTHOR]

Collagen is a triple-helical protein unique to the extracellular matrix, conferring rigidity and stability to tissues such as bone and tendon. For the [(PPG) 10 ] 3 collagen-mimetic peptide at room temperature, our molecular dynamics simulations show that these properties result in a remarkably ordered first hydration layer of water molecules hydrogen bonded to the backbone carbonyl (bb-CO) oxygen atoms. This originates from the following observations. The radius of gyration attests that the PPG triplets are organized along a straight line, so that all triplets (excepting the ends) are equivalent. The solvent-accessible surface area (SASA) for the bb-CO oxygens shows a repetitive regularity for every triplet. This leads to water occupancy of the bb-CO sites following a similar regularity. In the crystal-phase X-ray data, as well as in our 100 K simulations, we observe a 0-2-1 water occupancy in the P-P-G triplet. Surprisingly, a similar (0-1.7-1) regularity is maintained in the liquid phase, in spite of the sub-nsec water exchange rates, because the bb-CO sites rarely remain vacant. The manifested ordered first-shell water molecules are expected to produce a cylindrical electrostatic potential around the peptide, to be investigated in future work. [ABSTRACT FROM AUTHOR]

Simple Summary: The tests of the unicellular protozoan Nummulites distans (Cenozoic era, Paleogene period) were studied using X-ray diffraction. In addition, the images obtained using X-ray microtomography and scanning electron microscopy were analyzed. A high degree of the calcite crystal orientation ordering that the test consists of has been revealed. It is higher than that of calcite from the shells of the bivalve mollusk Placuna placenta, whose shell is formed by a special multicellular tissue. So, it is found that already unicellular organisms have strict control over the crystal arrangement. Unicellular protozoa form calcium carbonate tests. It is important to understand the features and mechanisms of its formation. This may shed light on the processes of shell formation in metazoans. One of the most important characteristics of the Protozoa carbonate test is the degree of crystal ordering that can be described by crystallographic texture. The crystallographic texture data of calcite in the foraminifera Nummulites distans (Deshayes) test from the Eocene deposits (Cenozoic, Paleogene) of the Crimea Peninsula are obtained using X-ray diffraction. A very strict orientation of the crystals is revealed. The calcite texture sharpness is several times greater than in the shells of the bivalve mollusk Placuna placenta (Linnaeus), measured by the same method. It also exceeds the crystallographic texture and sharpness of the same mineral in the shells of the bivalves of Mytilus galloprovincialis (Lamarck), studied by neutron diffraction. It is concluded that a high level of control during test formation is already characteristic of protozoa. Studying the processes involved in the formation of a very sharp crystallographic texture can become an important direction for creating nature-like materials with desired properties. [ABSTRACT FROM AUTHOR]

Cathaica is a genus of bradybaenid land snails occurring in China and is widespread in Shandong Province. Here we re-describe three species, C. pyrrhozona , C. fasciola and C. leei , and describe two new species, Cathaica fohuiensis Zhang sp. nov. and Cathaica multicostata Zhang sp. nov.. Geometric morphometric analyses demonstrate that C. pyrrhozona , C. fasciola , C. leei and C. fohuiensis are conchologically similar. Based on differences in their genitalia and molecular data, we consider C. pyrrhozona and C. fasciola to be distinct species. This re-establishes C. pyrrhozona as the type species of Cathaica. Cathaica leei can be distinguished based on its plate spiral whorl and wide umbilicus. The new species C. fohuiensis , with a conical shell and expanded vaginal base, can be distinguished from other Cathaica species based on morphological criteria and is robustly supported in the phylogenetic tree. The other new species, C. multicostata , possesses a strongly ribbed discoid shell and exhibits mucous glands that cluster tightly with the vagina. It is robustly supported in the phylogenetic tree and is the sister taxon to the other Cathaica species. Based on morphological characters and our molecular tree, Pliocathaica , represented here by P. buvigneri , P. pulveratricula and P. gansuica , is not monophyletic. [ABSTRACT FROM AUTHOR]

Ingestion of microplastics (MP) by suspension‐feeding bivalves has been well‐documented. However, it is unclear whether exposure to MP could damage the stomach and digestive gland (gut) of these animals, causing ramifications for organism and ecosystem health. Here, we show no apparent effects of nylon microfiber (MF) ingestion on the gut microbiome or digestive tissues of the blue mussel, Mytilus edulis. We exposed mussels to two low concentrations (50 and 100 particles/L) of either nylon MF or Spartina spp. particles (dried, ground marsh grass), ca. 250–500 μm in length, or a no particle control laboratory treatment for 21 days. Results showed that nylon MF, when aged in coarsely filtered seawater, developed a different microbial community than Spartina spp. particles and seawater, however, even after exposure to this different community, mussel gut microbial communities resisted disturbance from nylon MF. The microbial communities of experimental mussels clustered together in ordination and were similar in taxonomic composition and measures of alpha diversity. Additionally, there was no evidence of damage to gut tissues after ingestion of nylon MF or Spartina spp. Post‐ingestive particle processing likely mediated a short gut retention time of these relatively large particles, contributing to the negligible treatment effects. [ABSTRACT FROM AUTHOR]

Priapulids are marine, benthic ecdysozoan worms that feed using a distinctive toothed pharynx. While only a handful of lineages have survived to the present day, the Cambrian priapulid stem group left behind a rich record of articulated body fossils and characteristic trace fossils in the form of burrows. Recently, the fossil record of isolated priapulid cuticular elements including pharyngeal teeth has gained increased attention as a means of revealing cryptic priapulid taxa otherwise unknown among macrofossils. In this study, we focus on the ecological implications of shape variation in the teeth of extant and extinct priapulids, which display substantial morphological differences between taxa and life stages. We define a landmarking scheme to capture shape variation in priapulid teeth and apply it to our dataset, which includes a breadth of tooth specimens from extant macrofaunal and meiofaunal lineages alongside numerous Cambrian priapulid teeth preserved as isolated small carbonaceous fossils. Through ordination of the principal components of shape, we explore the priapulid tooth morphospace and find evidence that its occupancy has expanded since Cambrian times, indicating a corresponding expansion of the group's ecological niche. We also employ our geometric morphometric approach to make linear discriminant analysis-based taxon assignments based on tooth morphology, which can be helpful for classifying enigmatic "tooth taxa" known solely from fossil teeth. Finally, we use discriminant analysis to study tooth shapes from a functional perspective, considering known ecologies to characterize the ecological functions of unclassified isolated teeth. [ABSTRACT FROM AUTHOR]

In recent years, vitamin D3 has been revealed as an important regulator of reproductive processes in humans and livestock; however, its role in the female reproductive system of poultry is poorly known. The aim of this study was to examine vitamin D3 receptor (VDR and PDIA3) and metabolic enzyme (1α-hydroxylase and 24-hydroxylase) mRNA transcript and protein abundances, and protein localization within the hen ovary, oviductal shell gland, pituitary, liver, and kidney. We demonstrated, for the first time, the patterns of the relative mRNA and protein abundances of examined molecules in the ovary, dependent on follicle development and the layer of follicle wall, as well as in other examined organs. Immunohistochemically, PDIA3, 1α-hydroxylase, and 24-hydroxylase are localized in follicular theca and granulosa layers, luminal epithelium and tubular glands of the shell gland, pituitary, liver, and kidney. These results indicate that reproductive tissues have both receptors, VDR, primarily involved in genomic action, and PDIA3, probably participating in the rapid, non-genomic effect of vitamin D3. The finding of 1α-hydroxylase and 24-hydroxylase expression indicates that the reproductive system of chickens has the potential for vitamin D3 synthesis and inactivation, and may suggest that locally produced vitamin D3 can be considered as a significant factor in the orchestration of ovarian and shell gland function in hens. These results provide a new insight into the potential mechanisms of vitamin D3 action and metabolism in the chicken ovary and oviduct. [ABSTRACT FROM AUTHOR]

The hooded oyster, Saccostrea cucullata, is an economically important bivalve in Thailand with great potential for aquaculture production. Since its histological development remains unknown, we examined the organ development of field-collected S. cucullata associated with their shell size distributions from Libong Island, Thailand. The water quality parameters were not significantly different between the sampling areas except for the water temperature (p < 0.05). S. cucullata from the Stone Bridge (SB) site had smaller shell lengths and higher condition factors than those from Dugong Tourism by Drones (DT) except for the size of the organ. Histologically, the highest mean length of gill lamellae was 192.1±3.92 µm in 2.1-3 cm group. The thinnest of the mantle epithelium (73.78±3.08 µm in 4.1-5 cm group) of S. cucullata showed statistically significant difference between the sampled locations (Specific F value = 0.1783 and 0.8605 when p < 0.01 and p < 0.0001, respectively). The density of mucous-secreting cells (Msc) was more prominently distributed in the digestive gland than in other tissues. The 2.1-3 cm group or bigger had mature gonads with protandric characteristics, showing the rapid sexual differentiation in SB. Results obtained from this study improve the current knowledge of S. cucullata from natural environments, which potentially contributes to the establishment of its aquaculture. [ABSTRACT FROM AUTHOR]

Microplastic (MP) pollution is an emerging problem in many areas around the world and in coastal areas of Vietnam, requiring more studies dedicated to the accumulation of this pollutant in the food chain as well as its potential risk to human health. This study investigated MP levels in tissues of five common bivalve species collected from aquaculture areas along the coast of Vietnam. MPs were found in all bivalve samples, with average values of 10.84 ± 2.61 items/individual or 2.40 ± 1.34 items/g wet weight. Impacts of feeding habits of bivalves showed influences on MP abundance in the samples. Fibers were the dominant shape of MPs recorded, most of which accumulated in the gills and digestive glands of all bivalve samples, with the majority falling within the size range of 300—2000 µm. MPs found in all studied species had relatively similar chemical compositions, mainly composed of polypropylene (PP) and polyethylene (PE). In this study, a diverse diet consisting of different bivalve species and detailed data on the consumption rate of these species were used to assess the human health risk of MPs dedicated to the coastal communities of Vietnam. The results suggested a significant part of MP uptake by human could be via bivalve consumption, in which removing viscera and proper depuration should be applied prior to eating, thereby reducing the risk. [ABSTRACT FROM AUTHOR]