Crassostrea Ariakensis Research Articles

Exploring the feasibility of multi-elements coupled with chemometrics for discriminating the geographical origins of oysters (Crassostrea ariakensis)

This study explored the efficacy of multi-elements combined with chemometrics to discriminate the geographical origins of oysters (Crassostrea ariakensi). We determined 52 elements in 166 samples from four regions along the southeast coast of China. Significant regional variations of 51 elements were revealed (P < 0.05), while the principal component analysis (PCA) provided no clear regional delineations. The training models (n = 117) established on linear discriminant analysis (LDA), partial least square discriminant analysis (PLS-DA), and random forest (RF) uniformly achieved 100% predictive accuracy. The cross-validation accuracies of the final models (n = 166) derived from LDA, PLS-DA, and RF were 100%, 100%, and 99.4%, respectively. Even with the models simplified to 8 elements (Zn, Al, K, Cd, Cu, Rb, B, and Ag), high predictive and cross-validation accuracies were maintained, underscoring the robustness and algorithm flexibility of elemental profiling for accurately identifying the geographical origins of oysters.

The Effect of Heat Stress on Sensory Properties of Fresh Oysters: A Comprehensive Study Using E-Nose, E-Tongue, Sensory Evaluation, HS-SPME-GC-MS, LC-MS, and Transcriptomics.

Heat stress has received growing concerns regarding the impact on seafood quality. However, the effects of heat stress on the sensory properties of seafood remain unknown. In this study, the sensory properties of fresh oyster (Crassostrea ariakensis) treated with chronic heat stress (30 °C) for 8 weeks were characterized using electronic nose, electronic tongue, sensory evaluation, HS-SPME-GC-MS, LC-MS and transcriptomics. Overall, chronic heat stress reduced the overall sensory properties of oysters. The metabolic network constructed. based on enrichment results of 423 differential metabolites and 166 differentially expressed genes, showed that the negative effects of chronic heat stress on the sensory properties of oysters were related to oxidative stress, protein degradation, lipid oxidation, and nucleotide metabolism. The results of the study provide valuable insights into the effects of heat stress on the sensory properties of oysters, which are important for ensuring a sustainable supply of high-quality seafood and maintaining food safety.

Morphological and Molecular Analysis Identified a Subspecies of Crassostrea ariakensis (Fujita, 1913) along the Coast of Asia.

Crassostrea ariakensis (Fujita, 1913) is one of the most important economic and ecological oysters that is naturally distributed along the coast of Asia, separated by the Yangtze River estuary. They are usually compared as different populations, while there is no consensus on whether C. ariakensis in northern and southern areas should be considered as two species or subspecies. Here, we analyzed morphological characteristics, COI, 16s rRNA, mitogenome sequences, and species delimitation analysis (ASAP and PTP) to resolve the intraspecific taxonomic status of the C. ariakensis. Phylogenetic and ASAP analysis highlight that C. ariakensis was divided into N-type and S-type. PTP was unable to differentiate between the two types of C. ariakensis. The divergence time of N-type and S-type C. ariakinsis is estimated to be 1.6 Mya, using the relaxed uncorrelated lognormal clock method. Additionally, significant morphological differences exist between the two groups in terms of the adductor muscle scar color. Despite these differences, the COI (0.6%) and 16S rRNA (0.6%) genetic distance differences between N-type and S-type C. ariakensis has not yet reached the interspecific level. These results suggest that N-type and S-type C. ariakensis should be treated as different subspecies and renamed as C. ariakensis ariakensis subsp. nov and C. ariakensis meridioyangtzensis subsp. nov.

Combined ATAC-seq, RNA-seq, and GWAS analysis reveals glycogen metabolism regulatory network in Jinjiang oyster ( Crassostrea ariakensis).

Glycogen serves as the principal energy reserve for metabolic processes in aquatic shellfish and substantially contributes to the flavor and quality of oysters. The Jinjiang oyster ( Crassostrea ariakensis) is an economically and ecologically important species in China. In the present study, RNA sequencing (RNA-seq) and assay for transposase-accessible chromatin using sequencing (ATAC-seq) were performed to investigate gene expression and chromatin accessibility variations in oysters with different glycogen contents. Analysis identified 9 483 differentially expressed genes (DEGs) and 7 215 genes with significantly differential chromatin accessibility (DCAGs) were obtained, with an overlap of 2 600 genes between them. Notably, a significant proportion of these genes were enriched in pathways related to glycogen metabolism, including "Glycogen metabolic process" and "Starch and sucrose metabolism". In addition, genome-wide association study (GWAS) identified 526 single nucleotide polymorphism (SNP) loci associated with glycogen content. These loci corresponded to 241 genes, 63 of which were categorized as both DEGs and DCAGs. This study enriches basic research data and provides insights into the molecular mechanisms underlying the regulation of glycogen metabolism in C. ariakensis.

Aminotransferase Class I and II Gene Family in the Jinjiang Oyster (Crassostrea ariakensis): Genomewide Identification, Phylogenetic Analysis and Expression Profiles after Salinity Stress

Aminotransferases are enzymes found in living organisms that catalyze transfer reactions between amino acids and keto acids, crucial for amino acid metabolism and synthesis. Aminotransferase classes I and II play a vital role in regulating osmolarity, protecting cells, and improving metabolic homeostasis and cellular fitness. To investigate the characteristics of the aminotransferase class I and II gene family and their roles in osmotic pressure regulation in the Jinjiang oyster (Crassostrea ariakensis), the gene structure, chromosomal localization, and phylogeny were characterized and the genes’ expression in the gill under high-salt stress was analyzed. In this study, eighteen Aminotransferase class I and II genes, including SPTLCa and SPTLCb, SPTa and SPTb, ALAT2a and ALAT2b, KAT3a and KAT3b, and ASTa, ASTb and ASTc, were identified. The physicochemical properties of 11 family members were stable, with their instability factors less than 40. Subcellular localization prediction showed that aminotransferase classes I and II were localized in the cytoplasm or mitochondria. Chromosomal localization results showed that the 18 aminotransferase class I and II genes were located on eight chromosomes. All members of this gene family had the Aminotran_1_2 structural domain which is associated with osmotic pressure regulation by adjusting the conversion reaction between amino acids and keto acids. Most gene expressions showed an initial increase followed by a decrease from 0 h to 12 h when the oysters were challenged by acute stress using artificial seawater with a salinity of 40. However, the expression of CarAGT2 and CarKAT3b genes showed an increased trend with increasing stress time. This study systematically investigated the bioinformatics characteristics of the aminotransferase class I and II gene family in C. ariakensis and their role in osmotic pressure regulation, which provides scientific data for understanding the potential functions of these genes in physiological adaptation, thereby expanding the research on osmoregulation in bivalves.

Genome-wide mapping of regulatory variants for temperature- and salinity-adaptive genes reveals genetic basis of genotype-by-environment interaction in Crassostrea ariakensis

Regulatory variants in gene expression serve as bridges linking genetic variation and phenotypic plasticity. Environmental conditions typically influence the effects of regulatory variants on phenotypic plasticity; however, such genotype-by-environment interactions (G × E) are poorly understood. This study aimed to investigate the genetic basis of G × E in estuarine oyster (Crassostrea ariakensis), which is an important model animal for studying environmental adaption owing to its high plasticity and large intraspecific divergence. Genome-wide mapping of expression quantitative trait loci (eQTLs) for 23 environmental adaptive genes was performed for 256 estuarine oysters. We identified 1194 eQTL single nucleotide polymorphisms (eSNPs), including 433 cis-eSNPs in four genes and 722 trans-eSNPs in eight genes. The expression variation explanation of cis-eSNPs (9.95%) was significantly higher than that of trans-eSNPs (9.15%). We specifically showed cis- and trans-eSNPs with high linkage disequilibrium (LD) for Traf7, Slc6a5, Ggt, and Dap3. For example, we identified a cis-regulatory LD block containing 68 cis-eSNP and a trans-regulatory LD block, including 20 trans-eSNPs in Traf7. A high proportion (85%) of 40 vital eSNPs exhibited significant G × E effects. We identified crossing and nonparallel interactions of G × E, with the tag cis-eSNPs of Baat and Slc6a5 as representatives. Our results indicated that cis-eQTLs are highly conserved. This study provides insights into the understanding of adaptive evolutionary mechanisms and phenotypic response prediction to variable environments, as well as the genetic improvement for superior adaptive traits for genetic resource conservation and aquaculture.

Shell characterization and effects on cavity volume of wild Jinjiang oyster Crassostrea ariakensis in different estuaries of China

Shell characterization and effects on cavity volume of wild Jinjiang oyster Crassostrea ariakensis in different estuaries of China

Accelerated energy metabolism plays an important role in Heterosis and maternal effect of hybrids bred from southern and northern Suminoe oysters (Crassostrea ariakensis)

Accelerated energy metabolism plays an important role in Heterosis and maternal effect of hybrids bred from southern and northern Suminoe oysters (Crassostrea ariakensis)

Identification and Characterization of GYS and GSK3β Provides Insights into the Regulation of Glycogen Synthesis in Jinjiang Oyster Crassostrea ariakensis

Glycogen, a stored form of glucose, is an important form of energy for aquatic shellfish, contributing to the flavor and quality of the oyster. The glycogen synthase (GYS) and glycogen synthase kinase 3β (GSK3β) are two major enzymes in the glycogenesis. However, the information of the two genes in the Jinjiang oyster Crassostrea ariakensis remains limited. In this study, we identified the genes of GYS and GSK3β and further explored their function in the glycogen synthesis of C. ariakensis. The GYS and GSK3β were distributed in all tested tissues, and high expression of GYS and glycogen content were detected in the gonad, labial palp, hepatopancreas, and mantle, while the high expression of GSK3β was observed in the gill and adductor muscle. The expression of GYS was positively correlated with the glycogen content, while GSK3β was negatively correlated. Additionally, knockdown of GSK3β using RNAi decreased the GYS expression, revealing the negative regulatory effect of GSK3β on GYS. These findings enrich the research data of GSK3β and GYS involved in glycogen synthesis, providing valuable information for further research on the function of GSK3β and GYS in the glycogen synthesis process of oyster.

Gonad development and recruitment pattern of the oysters Crassostrea ariakensis and Crassostrea sikamea in a subtropical bay in China

The extent of oyster stocks and their habitat loss experienced on the Chinese coasts suggests that oyster restoration will be necessary to rebuild direct fisheries and recover lost ecosystem services. Limited understanding of oyster biology and ecology is among the potential barriers to successful restoration along the Chinese coasts. At a natural oyster bed in Jiantiao Bay, Sanmen County, China, the study compared gonad development and spawn duration of the Sumonie oyster Crassostrea ariakensis and the Kumamoto oyster Crassostrea sikamea through histological sections from May 2020 to March 2021. Their temporal and vertical recruitment patterns were simultaneously observed along an increasing tidal elevation gradient (0.1 m, 0.6 m, 1.1 m, 1.6 m, 2.1 m). The gonad index did not differ between the oysters (P>0.05), with the maximum values in June–August, but C. sikamea had a longer spawning duration (May–December) than C. ariakensis (May–October). Crassostrea ariakensis recruited to only the lower 3 tidal zones (0.1 m, 0.6 m, 1.1 m), and its recruits varied linearly and significantly as an inverse function of tidal elevation. Significant 2nd degree polynomial fits best described the relationships for C. sikamea recruits and tidal elevation. The greatest recruits were commonly observed at the mid intertidal zones (0.6 m, 1.1 m and 1.6 m). An evident vertical settlement pattern emerged for C. sikamea at both 1-day and 3-day experiments; the greatest settlement rates occurred in the 1.6 m tidal zone, intermediate rates occurred in the 1.1 m and 0.6 m, the lowest rates occurred in the 0.1 m and 2.1 m. The study concluded that C. sikamea sustained longer spawning and recruitment durations than C. ariakensis, and a strong zonation pattern in recruitment emerged; C. sikamea achieved its maximum recruits in the mid-tidal zone, while the recruits of C. ariakensis linearly decreased with increasing tidal elevation.

Adaptive divergence and underlying mechanisms in response to salinity gradients between two Crassostrea oysters revealed by phenotypic and transcriptomic analyses.

Comparing the responses of closely related species to environmental changes is an efficient method to explore adaptive divergence, for a better understanding of the adaptive evolution of marine species under rapidly changing climates. Oysters are keystone species thrive in intertidal and estuarine areas where frequent environmental disturbance occurs including fluctuant salinity. The evolutionary divergence of two sister species of sympatric estuarine oysters, Crassostrea hongkongensis and Crassostrea ariakensis, in response to euryhaline habitats on phenotypes and gene expression, and the relative contribution of species effect, environment effect, and their interaction to the divergence were explored. After a 2-month outplanting at high- and low-salinity locations in the same estuary, the high growth rate, percent survival, and high tolerance indicated by physiological parameters suggested that the fitness of C.ariakensis was higher under high-salinity conditions and that of C.hongkongensis was higher under low-salinity conditions. Moreover, a transcriptomic analysis showed the two species exhibited differentiated transcriptional expression in high- and low-salinity habitats, largely caused by the species effect. Several of the important pathways enriched in divergent genes between species were also salinity-responsive pathways. Specifically, the pyruvate and taurine metabolism pathway and several solute carriers may contribute to the hyperosmotic adaptation of C.ariakensis, and some solute carriers may contribute to the hypoosmotic adaptation of C.hongkongensis. Our findings provide insights into the phenotypic and molecular mechanisms underlying salinity adaptation in marine mollusks, which will facilitate the assessment of the adaptive capacity of marine species in the context of climate change and will also provide practical information for marine resource conservation and aquaculture.

Chromosome‐level genome and population genomic analysis provide insights into the evolution and environmental adaptation of Jinjiang oysterCrassostrea ariakensis

The Jinjiang oyster Crassostrea ariakensis, naturally distributing in estuarine regions with low salinity, is an important economic and ecological species in China. However, studies on its genomics and population genetics remain lacking. Here, we assembled the chromosome-level genome of a female C.ariakensis and re-sequenced 261 individuals from five locations in China representing three typical habitats. The C.ariakensis genome was 662.9Mb with contig N50 length of 5.9Mb using PacBio HiFi-CCS long reads, and 99.83% sequences were anchored onto 10 pseudochromosomes using Hi-C data. A total of 26,354 protein-coding genes were predicted. We identified three significantly expanded gene families which are closely associated with osmotic pressure regulation, including CDO, SLC13 and SDR. Population structure analysis revealed that the C.ariakensis from five locations were clustered into three typical groups (northern, southern and Shanghai) (K=3) and their phylogenetic relationship was consistently correlated to their geographical distribution. Furtherly, the differentiation between northern and southern groups was clearly demonstrated by estimated population differentiation coefficient (FST =0.1154), and the PSMC distribution showed the two groups of effective population size separated at 0.1Ma. Meanwhile gene flow from southern to Shanghai was detected. Selective sweep analysis between northern and southern group detected genes associated with heat response and salinity adaptation. This study could provide valuable genomic resources and information for further research on the molecular evolution, genetic breeding, biological function and evolutionary adaptation of C.ariakensis.

Comparison of growth, survival and fertility of the southern and northern populations of Crassostrea ariakensis and their hybrids in southern China

Crassostrea ariakensis is widely distributed in the estuaries of China and has the advantages of wide salinity adaptation and strong resistance, but the artificial aquaculture of C. ariakensis is mainly concentrated in southern China. Long-term geographical isolation resulted in genetic variation between the northern and southern C. ariakensis populations. In this study, the reproductive isolation between two independent population of C. ariakensis was evaluated by hybridization. Results showed that the fertilization rate, cleavage rate and D Larval rate of interpopulation hybrids (NS- northern ♂ × southern ♀ and SN- southern ♂ × northern ♀) were significantly lower than those of intrapopulation inbreed groups (SS and NN). Moreover, southern maternal larvae (SS and NS) have significant survival advantages. The growth trend between the two sites was very different in early stage (from 90th to 210th day), but it was consistent in late stage (from 210th to 480th day), with a significant decreasing trend of SS > NS > SN > NN. The survival rates of SN and NS was significantly higher than that of NN, indicating that the high temperature tolerance and stress resistance of hybrids were improved. The positive maternal effect advantages (MEAs) at most time points of both sites demonstrated that parental origin, especially the maternal origin, had a significant effect on the survival and growth of progeny. Hybrid advantages (HAs) for growth of both sites were opposite, and positive HAs of survival accounted for most of both sites, indicating that environmental conditions and survival could significantly affect the growth, and interpopulation hybrids did not necessarily always show positive HAs. Moreover, the maternal origin would affect the shell shape and shell hardness, resulted in NS similar to SS and SN similar to NN, respectively. Additionally, all interpopulation hybrids could produce mature gametes. These results confirmed that there was no serious reproductive isolation between the two populations. The southern maternal groups, especially SS, had better growth and survival advantages, could be used as good new strains for large-scale breeding in southern China, and also provided basic data for the commercial promotion of C. ariakensis in southern China.

Genome of the estuarine oyster provides insights into climate impact and adaptive plasticity

Understanding the roles of genetic divergence and phenotypic plasticity in adaptation is central to evolutionary biology and important for assessing adaptive potential of species under climate change. Analysis of a chromosome-level assembly and resequencing of individuals across wide latitude distribution in the estuarine oyster (Crassostrea ariakensis) revealed unexpectedly low genomic diversity and population structures shaped by historical glaciation, geological events and oceanographic forces. Strong selection signals were detected in genes responding to temperature and salinity stress, especially of the expanded solute carrier families, highlighting the importance of gene expansion in environmental adaptation. Genes exhibiting high plasticity showed strong selection in upstream regulatory regions that modulate transcription, indicating selection favoring plasticity. Our findings suggest that genomic variation and population structure in marine bivalves are heavily influenced by climate history and physical forces, and gene expansion and selection may enhance phenotypic plasticity that is critical for the adaptation to rapidly changing environments.

Evaluation of advantages in the growth, survival and reproductive aspects of triploid hybrids derived from Crassostrea gigas tetraploids and C. ariakensis diploids in northern China

Crossbreeding and polyploid breeding are two important tools for the genetic improvement of oysters, and their cross-application is expected to provide new benefits to oyster breeding. To evaluate the aquaculture traits of allotriploids between Crassostrea gigas and Crassostrea ariakensis, two triploid hybrids (TAG (diploid C. ariakensis ♀ × tetraploid C. gigas ♂) and TGA (tetraploid C. gigas ♀ × diploid C. ariakensis ♂)) were established. Phenotypic traits including growth, survival and reproduction were analyzed in two diploid hybrids (AG (diploid C. ariakensis ♀ × diploid C. gigas ♂) and GA (diploid C. gigas ♂ × diploid C. ariakensis ♀)) as controls. The results showed that TAG presented triploid advantage in fertilization rates and hatching rates, up to 11.34% and 26.50% respectively, while TGA did not. The survival rate of TAG and the shell height of TGA exhibited triploid advantage throughout the larval stage and were significantly higher (P < 0.05) than those of AG and GA at day 25. During the grow-out stage, triploid advantages appeared in the shell height of TAG and TGA, but only TAG showed triploid advantages in the survival rate. The triploid rates of TAG and TGA began to decrease during the grow-out stage, and reached 96.11% ± 4.41% and 90.56% ± 3.47%, respectively, at day 350. It was also found that the reproduction of TAG and TGA on day 350 was poor, manifesting as a high proportion of individuals with no gametes or a low number of gametes. Overall, TAG always presents triploid advantages in terms of growth and survival throughout the grow-out stage and shows potential value as a new resource of oyster farming or genetic improvement.

Effects of high hydrostatic pressure (HHP) and storage temperature on bacterial counts, color change, fatty acids and non-volatile taste active compounds of oysters (Crassostrea ariakensis)

The effects of HHP and storage temperature on bacterial counts, color, fatty acids and flavor compounds of oysters Crassostrea ariakensis were investigated. Counts of Vibrio vulnificus and Vibrio parahaemolyticus decreased to undetectable levels in ≥ 400 MPa-treated oysters. Storage at −20 °C significantly restrained microbial growth compared to 4 °C (P < 0.05). L* values of HHP-treated oysters significantly increased compared to raw oysters (P < 0.05). Storage slightly affected the color according to total color difference (ΔE*) values. Fatty acid profiles and betaine contents in 400 and 600 MPa-treated oysters at 0 and 15 d were almost the same as raw samples. Contents of total free amino acids (FAAs), Na+ and Ca2+ were significantly higher in 400 and 600 MPa-treated oysters than those in raw oysters at 0 d (P < 0.05), while the opposite results were observed in 5′-adenosine monophosphate (AMP), 5′-guanosine monophosphate (GMP), citric acid, succinic acid, K+ and PO43− (P < 0.05). At 400 and 600 MPa, FAAs significantly decreased after 15-d storage at 4 °C and −20 °C (P < 0.05), while no significant changes were observed in nucleotides, organic acids and inorganic ions.

Comparative study on the growth, survival, gonad development and trait segregation of F2 hybrids and their grandparent species (Crassostrea ariakensis and C. hongkongensis)

In previous studies, we showed that F1 hybrids of Crassostrea ariakensis and C. hongkongensis had faster growth and higher survival rates than the parent species. Further intraspecific crossing of F1 hybrids allowed us to further understand the law of trait segregation and indicated a potential direction for breeding of a new strain with high salinity tolerance and fast growth. In this study, we systematically analyzed the growth, survival, fertility and trait segregation of F2 hybrids and their grandparent species (C. ariakensis and C. hongkongensis) at two sites. Our results confirmed that there were no significant differences in fertilization, cleavage, D larval and survival rates among the three groups of larvae, but the shell heights of F2 hybrids and C. ariakensis were significantly higher than those of C. hongkongensis on the 12th and 16th days. At the high salinity site (Zhulin Pond), the shell heights and survival rates of the F2 hybrids were significantly higher than those of C. hongkongensis from the 90th to the 360th day. However, at the low salinity site (Dafeng River), the F2 hybrids consistently had higher shell heights than C. ariakensis, but there was no significant difference in the survival rates among the three groups. F2 hybrids were classified into three types based on size and number of holes on the gill water tubes, and only F2-A (like C. ariakensis) and F2-H/A (intermediate form) were confirmed to survive at the high salinity site. Moreover, three number of ITS-2 gene fragment were identified in the F2 hybrids, and only A (like C. ariakensis) and HA (like F1 hybrids) existed at the high salinity site. Paraffin sections of gonad tissue confirmed that all three types of F2 hybrids were fertile and could produce mature gametes. In summary, through this comprehensive comparative analysis, we confirmed that F2-A and F2-H/A hybrids had clear advantages in terms of high salinity tolerance and fast growth over their grandparent species, and had potential to be used as the foundations of a new strain.

Intertidal zonation and recruitment of oysters in the upstream of Jiantiao Bay, Sanmen County, Zhejiang Province

This study aims to explore the intertidal zonation pattern of oysters and examine the effect of breeding site and spat collector on oyster recruitment in the upstream of Jiantiao Bay, which is essential to understand the biology, ecology and resource conservation of oysters. The quantitative field observations identified Kumamoto oyster <italic>Crassostrea sikamea</italic>, Sumonie oyster <italic>C</italic>. <italic>ariakensis</italic> and Hongkong oyster <italic>C</italic>. <italic>hongkongensis</italic> by using the morphological and molecular methods. <italic>C</italic>. <italic>hongkongensis</italic> was first recorded on the coast of Zhejiang Province. <italic>Crasssostrea sikamea</italic> was present at all five tidal zones (1.4 m, 2.2 m, 3.0 m, 3.8m, 4.6 m above the standard level in Jiantao Bay hydraulic station), and its densities gradually declined along a decreasing tidal elevation gradient. The densities of <italic>C</italic>. <italic>sikamea</italic> were the highest at the 4.6 m tidal zone and were significantly greater than those at the 1.4 m and 2.2 m tidal zones (<italic>P</italic><0.05). <italic>Crassostrea ariakensis</italic> and <italic>C</italic>. <italic>hongkongensis</italic> were only present at the deepest two tidal zones (1.4 m and 2.2 m). Results from the oyster recruitment experiments indicated that both recruitment site and spat collector significantly affected the densities and shell height of oyster spat. There were high oyster recruitment in the Jiantiao Bay. The study conlcuded that concrete tiles were better spat collector than plastic ring. In general, the upstream site (S1) should be recommended as the suitable breeding ground for <italic>C</italic>. <italic>sikamea</italic>.

Effects of salinity on early activities of artificial hybridization between Crassostrea ariakensis and c . gigas

The hybridization experiments have been made between Crassostrea ariakensis and C. gigas several times. However, it is difficult to obtain a large number of hybrid offspring, which becomes the bottleneck of subsequent cross-breeding. To explore whether the production of hybrid larvae is affected by salinity, we investigated the effects of salinity (16, 20, 24, 28 and 32 psu) on the early activities of artificial hybridization between C. ariakensis and C. gigas at 23–24°C. In this study, the results showed that during artificial insemination, the appropriate salinity of high-quality gametes in C. ariakensis and C. gigas was 20–32 psu and 24–32 psu respectively. Besides, the fertilization rate of AG (C. ariakensis♀ × C. gigas♂) and GA (C. gigas♀ × C. ariakensis♂) at 24–28 psu was significantly (p < .05) higher than that at 16–20 psu. For incubation, the optimal salinity of embryo incubation was 28 psu, under which all embryos of AG and GA can develop rapidly to the D-larvae and yielded a high hatching rate. During larval rearing, the larval shell height and survival rate of AG were of no significant difference (p > .05) at all salinities, and the optimum salinity for larval growth and survival of GA was 24–28 psu. These findings can contribute to the increase in the hybrid progeny yield, which can serve as the new resource for genetic improvement of oyster germplasm.

Bioaccessibility-corrected health risk of heavy metal exposure via shellfish consumption in coastal region of China.

A systematic investigation into bioaccessible heavy metals in shellfish Crassostrea ariakensis, Chlamys farreri, and Sinonovacula constricta from coastal cities Shenzhen, Zhoushan, Qingdao, and Dandong was carried out to assess the potential health risk to residents in coastal regions in China. The bioaccessible fractions of heavy metals were (μg‧g-1): Zn (0.63-15.01), Cu (0.10-12.91), Cd (0.01-0.64), As (0.11-0.33), Cr (0.07-0.12), Pb (0.01-0.03). The bioaccessibilities of heavy metals were Cr 61.86%, inorganic As (iAs) 60.44%, Pb 55.74%, Cu 46.83%, Zn 28.16%, and Cd 24.99%. As for child and adult, the bioaccessibility-corrected estimated daily intakes were acceptable and the non-carcinogenic risks posed by heavy metals were not obvious. The carcinogenic risks posed by bioaccessible heavy metals at the fifth percentile were 10-fold higher than the acceptable level (10-4), with iAs and Cd to be the major contributors, regardless of child or adult. The probabilistic estimation showed the low risk of shellfish consumption, which was verified by higher values of maximum allowable consumption rate and monthly meals at the 95 percentile; while some control of consumption rate and monthly meals was necessary for reducing heavy metal exposure of most shellfish samples, except for the safe consumption of S.constricta for both child and adult in Qingdao and Shenzhen, China.