Aplacophoran traits in the late Ordovician septemchitonid polyplacophorans.

A sample of phosphatized, originally calcareous, mollusk shells from the Katian age uppermost Mójcza Limestone at its type locality yielded a few hundred polyplacophoran plates. The chelodids are very rare among them. Three septemchitonid species dominate. They represent a gradation from underived steep roof-like plates to almost cylindrical ones, leaving only a narrow ventral slit for the foot. Apparently, this represents the first step toward the extremely derived 'segmented clam' Bauplan of the Silurian Carnicoleus, with plates completely closed at the venter except for the mouth and anal openings. To enable growth, the plates became thinner and more flexible (or perhaps resorbed) along the dorsum. The tendency toward reduction of the ventral gap of the plates in the early Paleozoic septemchitonid polyplacophorans implies their lack of ability to cling to the substrate with a muscular foot. In compensation, their plates changed toward a more efficient protective function, covering the animal body sides more and more completely. This may explain the origin of the ventral furrow of extant solenogasters hiding the rudimentary foot. An opposite route was chosen by the coeval Acaenoplax lineage, in which the plates did not contact each other, exposing much of the soft body on the dorsum. In both cases the animals appeared to be worm-like, perhaps representing different ways of evolution from the Paleozoic chitons to the extant aplacophorans.

Phosphorylated chitin from shrimp shell waste: A robust solution for cadmium remediation.

In this work, chitin (CT) was isolated from shrimp shell waste (SSW) and was then phosphorylated using diammonium hydrogen phosphate (DAP) as a phosphorylating agent in the presence of urea. The prepared samples were characterized using Scanning Electron Microscopy (SEM) and EDX-element mapping, Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA/DTG), conductometric titration, Degree of Substitution (DS) and contact angle measurements. The results of characterization techniques reveal the successful extraction and phosphorylation of chitin. The charge content of the phosphorylated chitin (P-CT) was 1.510 mmol·kg-1, the degree of substitution of phosphorus groups grafted on the CT surface achieved the value of 0.33. The adsorption mechanisms appeared to involve electrostatic attachment, specific adsorption (CdO or hydroxyl binding), and ion exchange. Regarding the adsorption of Cd2+, the effect of the adsorbent mass, initial concentration of Cd2+, contact time, pH, and temperature were studied in batch experiments, and optimum values for each parameter were identified. The experimental results revealed that P-CT enhanced the Cd2+ removal capacity by 17.5 %. The kinetic analyses favored the pseudo-second-order model over the pseudo-first-order model for describing the adsorption process accurately. Langmuir model aptly represented the adsorption isotherms, suggesting unimolecular layer adsorption with a maximum capacity of 62.71 mg·g-1 under optimal conditions of 30 °C, 120 min, pH 8, and a P-CT dose of 3 g·L-1. Regeneration experiments evidenced that P-CT can be used for 6 cycles without significant removal capacity loss. Consequently, P-CT presents an efficient and cost-effective potential biosorbent for Cd2+ removal in wastewater treatment applications.

Transcriptomic and Physiological Analysis Reveal Melanin Synthesis-Related Genes and Pathways in Pacific Oysters (Crassostrea gigas).

Shell color is one of the shell traits of molluscs, which has been regarded as an economic trait in some bivalves. Pacific oysters (Crassostrea gigas) are important aquaculture shellfish worldwide. In the past decade, several shell color strains of C. gigas were developed through selective breeding, which provides valuable materials for research on the inheritance pattern and regulation mechanisms of shell color. The inheritance patterns of different shell colors in C. gigas have been identified in certain research; however, the regulation mechanism of oyster pigmentation and shell color formation remains unclear. In this study, we performed transcriptomic and physiological analyses using black and white shell oysters to investigate the molecular mechanism of melanin synthesis in C. gigas. Several pigmentation-related pathways, such as cytochrome P450, melanogenesis, tyrosine metabolism, and the cAMP signaling pathway were found. The majority of differentially expressed genes and some signaling molecules from these pathways exhibited a higher level in the black shell oysters than in the white, especially after L-tyrosine feeding, suggesting that those differences may cause a variation of tyrosine metabolism and melanin synthesis. In addition, the in vitro assay using primary cells from mantle tissue showed that L-tyrosine incubation increased cAMP level, gene and protein expression, and melanin content. This study reveals the difference in tyrosine metabolism and melanin synthesis in black and white shell oysters and provides evidence for the potential regulatory mechanism of shell color in oysters.

Synthesis and characterization of hydroxyapatite self-assembled nanocomposites on graphene oxide sheets from seashell waste: A green process for regenerative medicine.

Bone transplantation is the second most common transplantation surgery in the world. Therefore, there is an urgent need for artificial bone transplantation to repair bone defects. In bone tissue engineering, hydroxyapatite (HA) plays a major role in bone graft applications. This study deals with a facile method for synthesizing HA hexagonal nanorods from seashells by a solid-state hydrothermal transition process. The synthesized HA nanorods (∼2.29 nm) were reinforced with carbon nanotube and chitosan on graphene oxide sheets with polymeric support by in-situ synthetic approach. Among the synthesized nanocomposites viz., hydroxyapatite-graphene oxide (HA-GO), hydroxyapatite-graphene oxide-chitosan (HA-GO-CS), hydroxyapatite-graphene oxide-chitosan-carbon nanotube-polylactic acid (HA-GO-CS-CNT-PLA). Among them, the HA-GO-CS-CNT-PLA composite exhibits micro and macro porosity (∼200 to 600 µm), higher mechanical strength, (Hardness ∼90.5 ± 1.33 MPa; Tensile strength 25.62 MPa), and maximum cell viability in MG63 osteoblast-like cells (80%). The self-assembled hybrid-nanocomposite of HA-GO-CS-CNT-PLA is a promising material for bone filler application and could efficiently utilize seashell waste through the green process.

Chemical extraction of chitin from American lobster (Homarus americanus) shells optimized through response surface methodology.

Chitin extraction from the shells of American lobsters (Homarus americanus) was optimized through the use of response surface methodology (RSM). The demineralization step was optimized to minimize the ash content of shell samples and the deproteination step was optimized to minimize the protein content of the chitin product. At a laboratory scale, one set of optimized conditions for the demineralization step was 7.35 % w/w acetic acid at a 40 mL/g of powdered lobster shell ratio for 15 min; this lowered the ash content from 39.62 % to 0.41 ± 0.08 %. A set of optimized conditions for the deproteination step at a similar scale was 4 % w/w sodium hydroxide at a 43 mL/g demineralized shell ratio heated to 95 °C for 83 min. These conditions were indicated to entirely remove protein from the resultant chitin. Average yields under optimized conditions were 23.43 ± 1.75 % for demineralization and 30.33 ± 0.02 % for deproteination, though a demineralization reaction with larger biomass input had a higher yield at 40.31 %.

Proteomic analysis of shell matrix proteins from the chiton Acanthopleura loochooana.

Most molluscs have mineralized shells to protect themselves. Although the remarkable mechanical properties of shells have been well-studied, the origin of shells is still elusive. Chitons are unique in molluscs because they are shelly Aculifera which diverged from Conchifera (comprising all the shell-bearing classes of molluscs) in the early pre-Cambrian. We developed a method to extract shell proteins from chiton shell plates (removing embedded soft tissues) and then compared the shell proteome to that of Conchifera groups. Sixteen shell matrix proteins from Acanthopleura loochooana were identified by proteomics, in which Nacrein-like, Pif-like proteins, and protocadherin were found. Additional evidences from shell proteome in another species Chiton densiliratus and comparative sequence alignment in five chitons supported a conserved biomineralization toolkit in chitons. Our findings shed light on the evolution of mineralization in chitons and pose a hypothesis that ancestral molluscs have already evolved biomineralization toolkits, which may facilitate the formation of mineralized shells.

Radula and Shell Microstructure Variations are Congruent with a Molecular Estimate of Shallow-Water Japanese Chitons.

Variations of the radula and shell microstructures in 33 species of Japanese chiton were investigated along with molecular phylogenetic trees. The molecular phylogenetic trees indicated that Chitonida was composed of four clades, of which two clades formed Acanthochitonina and corresponded to Mopalioidea and Cryptoplacoidea, respectively, and the other clades formed Chitonina. In the radula, the shapes of the central and centro-lateral teeth and the petaloid process varied greatly among species or genera and were useful for the identification of particular species or genera. The presence of accessory and petaloid processes and the cusp shape were relatively conserved and useful for recognizing particular genera or even suborders. In the valves, four to six shell layers were found at the section, but the ventral mesostracum was not observed in Acanthochitonina. The shell microstructures in the ventral sublayer of the tegmentum varied at suborder, but those in the other layers were almost constant. The megalaesthete chamber type varied at superfamily and was helpful to identify particular families or superfamilies. The characteristics of the shell layers and shell microstructures appear to be a synapomorphy shared by the members of Acanthochitonina. The classification within Chitonina needs to be reexamined because the variations of the cusp shape and megalaesthete chamber type were relatively large and did not correspond to the current classification. Callochiton formed a sister group with Chitonida and would be equally closely related to Chitonina and Acanthochitonina because of possessing a mosaic of characteristics from both.

Exploring the relationship between environmental drivers and the manifestation of fibropapillomatosis in green turtles (Chelonia mydas) in eastern Brazil.

Fibropapillomatosis (FP) is a disease characterized by epithelial tumors that can impede life-sustaining activities of sea turtles, especially green turtles (Chelonia mydas). FP is caused by a herpesvirus, but environmental factors are also thought to play a role in triggering FP tumor growth. In this study, we evaluate the epidemiology of FP tumors in green turtles along the coast of Espírito Santo, Brazil, a region where juvenile green turtles are known to aggregate with high FP prevalence. A dataset comprising 2024 beach-cast green turtles recorded through daily beach surveys on 400 km of coastline from 2018 to 2021 (inclusive) was evaluated. FP tumors were recorded in 40.9% of the individuals in this dataset, and presence of FP tumors was predicted by individual variables (presence of marine leeches, stranding code, curved carapace length, body mass-size residual) and characteristics of the stranding site (distance to nearest metallurgical plant, mean sea surface salinity (SSS), annual range of sea surface temperature (SST)). Additionally, a second dataset comprising detailed information about the size and anatomical distribution of tumors in 271 green turtles with FP from the same region was evaluated. Hierarchical clustering analysis revealed these turtles could be classified in three groups according to the anatomical distribution of their tumors, and in turn the group to which each turtle was assigned could be predicted by the study period (2010-2014 vs. 2018-2022) and by characteristics of the stranding/capture site (green turtle stranding density, mean sea surface chlorophyll-a concentration, mean SSS, mean SST, annual range of SST). These results corroborate that individual and environmental factors play a significant role driving FP epidemiology. Furthermore, the results suggest that rather than behaving as a single entity, FP may be seen as a mosaic of distinct anatomical patterns that are not necessarily driven by the same environmental factors.

A sustainable one-pot method to transform seashell waste calcium carbonate to osteoinductive hydroxyapatite micro-nanoparticles.

We have developed a straightforward, one-pot, low-temperature hydrothermal method to transform oyster shell waste particles (bCCP) from the species Crassostrea gigas (Mg-calcite, 5 wt% Mg) into hydroxyapatite (HA) micro/nanoparticles. The influence of the P reagents (H3PO4, KH2PO4, and K2HPO4), P/bCCP molar ratios (0.24, 0.6, and 0.96), digestion temperatures (25-200 °C), and digestion times (1 week-2 months) on the transformation process was thoroughly investigated. At 1 week, the minimum temperature to yield the full transformation significantly reduced from 160 °C to 120 °C when using K2HPO4 instead of KH2PO4 at a P/bCCP ratio of 0.6, and even to 80 °C at a P/bCCP ratio of 0.96. The transformation took place via a dissolution-reprecipitation mechanism driven by the favorable balance between HA precipitation and bCCP dissolution, due to the lower solubility product of HA than that of calcite at any of the tested temperatures. Both the bCCP and the derived HA particles were cytocompatible for MG-63 human osteosarcoma cells and m17.ASC murine mesenchymal stem cells, and additionally, they promoted the osteogenic differentiation of m17.ASC, especially the HA particles. Because of their physicochemical features and biological compatibility, both particles could be useful osteoinductive platforms for translational applications in bone tissue engineering.

Comparative physicochemical analysis of chitin quality of the two tagmata in the exoskeleton of the horseshoe crab Limulus polyphemus.

Recently, chitin biopolymer has received much attention as a wide variety of biomedical application for this and its derivatives have been reported, in fact, the study of non-conventional species as alternative sources of them compounds has taken particular interest. Here, we present a comparative physicochemical survey of the two tagmata in the exoskeleton of the horseshoe crab Limulus polyphemus: the prosoma and the opisthosoma, collected in Yucatán, Mexico. The characterization included CHNSO analysis, FTIR, TGA, DSC, XRD, and SEM. The CHNSO analysis revealed that C is present in the highest proportion (∼45 %) and that chemical composition did not show significant differences (P < 0.05) between the two tagmata. FTIR spectra of two tagmata presented a wide characteristic band of the chitin between 3600 and 3000 cm-1, confirming the presence of this biopolymer in the exoskeleton studied. TGA and DTGA profiles resulted very similar for both tagmata being the residual mass at 650 °C of around 30 % for both samples; these values were associated to the presence of minerals. SEM micrographs showed a porous matrix with infinite large number of irregularly shaped particles. Results show that both tagmata are made up of chitin, and they seem to have a high mineral content.

Shell Disease Syndrome Is Associated with Reduced and Shifted Epibacterial Diversity on the Carapace of the Crustacean Cancer pagurus.

Cancer pagurus is highly susceptible to shell disease syndrome. However, little is known about concomitant changes in the epibacterial community. We compared the bacterial communities of black spot affected and nonaffected areas of the carapace by amplicon sequencing of 16S rRNA genes and 16S rRNA. Within each spot, bacterial communities of affected areas were less diverse compared to communities from nonaffected areas. Communities of different affected spots were, however, more divergent from each other, compared to those of different nonaffected areas. This indicates a reduced and shifted microbial community composition caused by the black spot disease. Different communities found in black spots likely indicate different stages of the disease. In affected areas, Flavobacteriaceae rose to one of the most abundant and active families due to the increase of Aquimarina spp., suggesting a significant role in shell disease syndrome. We isolated 75 bacterial strains from diseased and healthy areas, which are primarily affiliated with Proteobacteria and Bacteroidetes, reflecting the dominant phyla detected by amplicon sequencing. The ability to degrade chitin was mainly found for Gammaproteobacteria and Aquimarina spp. within the Flavobacteriia, while the ability to use N-acetylglucosamine, the monomer of the polysaccharide chitin, was observed for most isolates, including many Alphaproteobacteria. One-third of the isolates, including most Aquimarina spp., showed antagonistic properties, indicating a high potential for interactions between the bacterial populations. The combination of bacterial community analysis and the physiological properties of the isolates provided insights into a functional complex epibacterial community on the carapace of C. pagurus. IMPORTANCE In recent years, shell disease syndrome has been detected for several ecologically and economically important crustacean species. Large proportions of populations are affected, e.g., >60% of the widely distributed species Cancer pagurus in different North Sea areas. Bacteria play a significant role in the development of different forms of shell disease, all characterized by microbial chitinolytic degradation of the outer shell. By comparing the bacterial communities of healthy and diseased areas of the shell of C. pagurus, we demonstrated that the disease causes a reduced bacterial diversity within affected areas, a phenomenon co-occurring also with many other diseases. Furthermore, the community composition dramatically changed with some taxa rising to high relative abundances and showing increased activity, indicating strong participation in shell disease. Characterization of bacterial isolates obtained from affected and nonaffected spots provided deeper insights into their physiological properties and thus the possible role within the microbiome.

Turning Seashell Waste into Electrically Conductive Particles.

Biomaterials such as seashells are intriguing due to their remarkable properties, including their hierarchical structure from the nanometer to the micro- or even macroscopic scale. Transferring this nanostructure to generate nanostructured polymers can improve their electrical conductivity. Here, we present the synthesis of polypyrrole using waste seashell powder as a template to prepare a polypyrrole/CaCO3 composite material. Various synthesis parameters were optimized to produce a composite material with an electrical conductivity of 2.1 × 10-4 ± 3.2 × 10-5 S/cm. This work presents the transformation of waste seashells into sustainable, electronically conductive materials and their application as an antistatic agent in polymers. The requirements of an antistatic material were met for a safety shoe sole.

An acidic protein, Hf15, from Haliotis fulgens involved in biomineralization.

Biomineralization leads to the hardening of mineralized materials, such as the shell of Mollusk, to fulfill a wide range of functions, such as (but not limited to) skeletal support, protection of the soft tissues, navigation, etc. The study of the proteins responsible for this process, shell matrix proteins (SMPs), allows addressing questions related to structure-function relationship and to the mechanism of mineral formation, which is limited in gastropod species. In this study, a low molecular weight protein was isolated from the insoluble fraction after decalcification with acetic acid of the shell of Haliotis fulgens and, named Hf15. The unglycosylated protein has a theoretical molecular weight of 15 kDa, it possesses calcium and chiting binding properties. Hf15 can precipitate calcium carbonate in vitro in presence of different salts. Analysis by LC-MS of the five peptide sequences of Hf15 generated by trypsinization revealed that two peptides displayed homology to an uncharacterized protein 3-like from Haliotis rufescens, Haliotis asinia and H. sorenseni. The results obtained indicated that Hf15 is a novel SMP involved in shell mineralization in Haliotis fulgens.

Optimized Sensory Units Integrated in the Chiton Shell.

The first step for animals to interact with external environment is to sense. Unlike vertebrate animals with flexibility, it is challenging for ancient animals that are less flexible especially for mollusca with heavy shells. Chiton, as an example, has eight overlapping shells covering almost the whole body, is known to incorporate sensory units called aesthetes inside the shell. We used micro-computed tomography combined with quantitative image analysis to reveal the optimized shell geometry to resist force and the aesthetes' global distribution at the whole animal levels to facilitate sense from diverse directions both in the seawater and air. Additionally, shell proteomics combined with transcriptome reveals shell matrix proteins responsible for shell construction and potentially sensory function, highlighting unique cadherin-related proteins among mollusca. Together, this multi-level evidence of sensory units in the chiton shell may shed light on the formation of chiton shells and inspire the design of hard armor with sensory function.

Molecular cloning and functional characterization of KCNQ1 in shell biomineralisation of pearl oyster Pinctada fucata martensii.

KCNQ1, a voltage-gated potassium ion channel, plays an important role in various physiological processes, including osteoblast differentiation in higher animals. However, its function in lower invertebrates such as marine shellfish remains poorly understood. Pearl oysters, such as P. fucata martensii, are ideal for studying biomineralisation. In this study, a full-length cDNA of KCNQ1 from P. fucata martensii (PfKCNQ1) was obtained, and its function in shell formation was investigated. The full-length 3945 bp cDNA of PfKCNQ1 included an open reading frame (ORF) of 1944 bp encoding a polypeptide of 647 amino acids. Multiple sequence alignment revealed high homology with KCNQ1 from other species, with six transmembrane domains (S1 - S6) and a pore (P) region. Expression pattern analysis showed that PfKCNQ1 was expressed in all tested tissues, with highest expression in mantle and heart, and shell notching induced PfKCNQ1 expression. Silencing PfKCNQ1 expression inhibited PfKCNQ1 expression and downregulated four biomineralisation-related genes (Shematrin, Pif80, N16 and MSI60). Disordered crystals or "hollows" were visible in the shell ultrastructure by scanning electron microscopy following PfKCNQ1 knockdown. The results suggested that PfKCNQ1 may participate in or regulate biomineralisation and shell formation in pearl oyster.

Structural characterization and regulation of the mechanical properties of the carapace cuticle in tri-spine horseshoe crab (Tachypleus tridentatus).

Horseshoe crab (order Xiphosura) has a large and thick carapace that has evolved as a protective tool to defend against predators and resist impacts from surf-zone turbulence. The naturally occurring spatial variation in the mechanical properties of the carapace cuticle need to be investigated to understand their regulatory mechanism and the underlying design strategies. In this work, we used a combination of high-resolution optical microscopy, scanning electron microscopy, (SEM) and energy-dispersive X-ray spectroscopy (EDS) to evaluate the multiscale microstructure and elemental composition of the cuticle of tri-spine horseshoe crab (Tachypleus tridentatus). The moduli, ultimate strengths, and failure strains of the three individual layers and the entire cuticle were systematically characterized in both the dry and hydrated states. The failure behaviors and energy absorption of the cuticle involved stress stiffening, toughness mechanism and environmental adaptation were analyzed qualitatively and quantitatively and then correlated with the morphological features in different cuticle regions. The mechanical properties are primarily influenced by the endocuticle thickness ratio; a higher thickness ratio corresponds to more stacking of the vertical lamellae, leading to a lower modulus, weaker strength, and greater elongation of the endocuticle. Radial energy is absorbed primarily by the endocuticle, with the energy absorbed in the radial direction being nearly twice that absorbed in the circumferential direction. This is attributed to the larger failure strain and relatively small decrease in the stress plateau in the radial direction. The findings provide a deeper understanding of how nature modulates the cuticle's mechanical properties and inspiration for developing high-performance synthetic composites.

Application of Nano-Hydroxyapatite Derived from Oyster Shell in Fabricating Superhydrophobic Sponge for Efficient Oil/Water Separation.

The exploration of nonhazardous nanoparticles to fabricate a template-driven superhydrophobic surface is of great ecological importance for oil/water separation in practice. In this work, nano-hydroxyapatite (nano-HAp) with good biocompatibility was easily developed from discarded oyster shells and well incorporated with polydimethylsiloxane (PDMS) to create a superhydrophobic surface on a polyurethane (PU) sponge using a facile solution-immersion method. The obtained nano-HAp coated PU (nano-HAp/PU) sponge exhibited both excellent oil/water selectivity with water contact angles of over 150° and higher absorption capacity for various organic solvents and oils than the original PU sponge, which can be assigned to the nano-HAp coating surface with rough microstructures. Moreover, the superhydrophobic nano-HAp/PU sponge was found to be mechanically stable with no obvious decrease of oil recovery capacity from water in 10 cycles. This work presented that the oyster shell could be a promising alternative to superhydrophobic coatings, which was not only beneficial to oil-containing wastewater treatment, but also favorable for sustainable aquaculture.

The novel matrix protein hic7 of hyriopsis cumingii participates in the formation of the shell and pearl.

Shell matrix proteins have important roles in the biomineralization of shells. In this study, we isolated and identified a novel shell matrix protein gene, hic7, from the mussel Hyriopsis cumingii. The cDNA of hic7 was 459 bp long, including a 240-bp open reading frame. It encoded a 79 amino acid-long protein, with amino acids 1-19 constituting the signal peptide. The resulting hic7 is rich in cysteine (16.5%). After removing the signal peptide, the molecular weight was 8.85 kDa and the theoretical isoelectric point was 6.34, indicating that hic7 is a weakly acidic shell matrix protein. Hic7 is mainly expressed in the mantle tissue of H. cumingii. In situ hybridization showed hic7 signals at the edge and dorsal region of the mantle outer fold, indicating that it is related to the formation of the prismatic and nacreous layer of the shell. RNA interference indicated that when hic7 was inhibited by 80%, the crystal morphology of the prism and nacre layers of the shell were irregular and disordered. In addition, the expression of hic7 during the early development of the pearl sac indicated that it has an important role in the transformation of calcium carbonate crystals from a disordered to an orderly deposition pattern. These results suggest that matrix protein hic7 take part in constructing the framework of crystal nucleation and regulating the calcium carbonate crystal morphology of the nacreous and prismatic layers of shells and pearls.

Novel globular C1q domain-containing protein (PmC1qDC-1) participates in shell formation and responses to pathogen-associated molecular patterns stimulation in Pinctada fucata martensii.

The C1q protein, which contains the globular C1q (gC1q) domain, is involved in the innate immune response, and is found abundantly in the shell, and it participates in the shell formation. In this study, a novel gC1q domain-containing gene was identified from Pinctada fucata martensii (P. f. martensii) and designated as PmC1qDC-1. The full-length sequence of PmC1qDC-1 was 902 bp with a 534 bp open reading frame (ORF), encoding a polypeptide of 177 amino acids. Quantitative real-time PCR (qRT-PCR) result showed that PmC1qDC-1 was widely expressed in all tested tissues, including shell formation-associated tissue and immune-related tissue. PmC1qDC-1 expression was significantly high in the blastula and gastrula and especially among the juvenile stage, which is the most important stage of dissoconch shell formation. PmC1qDC-1 expression was located in the outer epithelial cells of mantle pallial and mantle edge and irregular crystal tablets were observed in the nacre upon knockdown of PmC1qDC-1 expression at mantle pallial. Moreover, the recombined protein PmC1qDC-1 increased the rate of calcium carbonate precipitation. Besides, PmC1qDC-1 expression was significantly up-regulated in the mantle pallial at 6 h and was significantly up-regulated in the mantle edge at 12 h and 24 h after shell notching. The expression level of PmC1qDC-1 in mantle edge was significantly up-regulated at 48 h after LPS stimulation and was significantly up-regulated at 12 h, 24 h and 48 h after poly I:C stimulation. Moreover, PmC1qDC-1 expression was significantly up-regulated in hemocytes at 6 h after lipopolysaccharide (LPS) and poly I:C challenge. These findings suggest that PmC1qDC-1 plays a crucial role both in the shell formation and the innate immune response in pearl oysters, providing new clues for understanding the shell formation and defense mechanism in mollusk.

Advances in the preparation and assessment of the biological activities of chitosan oligosaccharides with different structural characteristics.

Chitosan oligosaccharides (COSs) are widely used biopolymers that have been studied in relation to a variety of abnormal biological activities in the food and biomedical fields. Since different COS preparation technologies produce COS compounds with different structural characteristics, it has not yet been possible to determine whether one or more chito-oligomers are primarily responsible for the bioactivity of COSs. The inherent biocompatibility, mucosal adhesion and nontoxic nature of COSs are well documented, as is the fact that they are readily absorbed from the intestinal tract, but their structure-activity relationship requires further investigation. This review summarizes the methods used for COS preparation, and the research findings with regard to the antioxidant, anti-inflammatory, anti-obesity, bacteriostatic and antitumour activity of COSs with different structural characteristics. The correlation between the molecular structure and bioactivities of COSs is described, and new insights into their structure-activity relationship are provided.