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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. [ABSTRACT FROM AUTHOR]

Peptides from oysters have several bioactive functions. In this study, we identified antioxidant peptides from oysters (Crassostrea rivularis) and investigated their structure–function relationship. We used an 8 kDa molecular‐weight (MW) cut‐off membrane and semiprep reversed‐phase liquid chromatography to collect five peptides (F1–F5) and identified the highest‐abundance ion‐peak sequences AWVDY (F1), MSFRFY(F2), EPLRY(F3), RKPPWPP(F4), and YAKRCFR(F5) having MWs of 652, 850, 676, 877, and 943 Da, respectively, using ultra‐performance liquid chromatography‐quadrupole/time‐of‐flight tandem mass spectrometry. These peptides exhibited high antioxidant activities, similar to butylated hydroxytoluene, reduced glutathione, and ascorbic acid. F5 demonstrated the highest scavenging activity for DPPH radicals (IC50 = 21.75 μg/ml), hydroxyl radicals (IC50 = 18.75 μg/ml), and superoxide radicals (IC50 = 11.00 μg/ml), while F3 demonstrated the highest reducing power. Furthermore, F5 significantly protected Caco‐2 cells from H2O2‐induced oxidative damage. These results suggest that the antioxidant peptide F5 is a promising food additive that protects against oxidative damage. [ABSTRACT FROM AUTHOR]

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 662.9 Mb with contig N50 length of 5.9 Mb 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 0.1 Ma. 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Bivalve habitat restoration is growing in geographic extent and scale globally. While addressing the wide‐scale loss of these biogenic habitats is still a key motivation behind restoration efforts, stakeholders and funders are increasingly drawn to shellfish restoration for the many ecosystem services these habitats provide.There is clear evidence for the provision of ecosystem services from species targeted for restoration in the USA, in particular Crassostrea virginica. Ecosystem services, however, remain largely unquantified or even undescribed for the majority of other species targeted for restoration.A structured review of the literature was undertaken and supplemented by expert knowledge to identify which ecosystem services are documented in the following other bivalve species targeted for restoration: Ostrea edulis, Ostrea angasi, Crassostrea rhizophorae, Perna canaliculus, Modiolus modiolus, Mytilus edulis, Mytilus platensis, Crassostrea gigas, Ostrea denselamellosa, Crassostrea ariakensis, and Crassostrea sikamea.Key knowledge gaps in quantifying ecosystem services and the ecosystem engineering properties of habitat‐building bivalves contributing to the provision of ecosystem services were identified. Ecosystem services with the potential to be widely applicable across bivalve habitat‐building species were identified.Though there is evidence that many of the ecosystem engineering properties that underpin the provision of ecosystem services are universal, the degree to which services are provided will vary between locations and species. Species‐specific, in situ, studies are needed in order to avoid the inappropriate transfer of the ecosystem service delivery between locations, and to further build support and understanding for these emerging targets of restoration. [ABSTRACT FROM AUTHOR]

Abstract: Crude polysaccharide was prepared from Crassostrea rivularis by 30% (w/v) potassium hydroxide solution at 90°C for 120 min. Three fractions (OG1, OG2, and OG3) were purified by DEAE‐52 cellulose and Sepharose 2B gel column chromatography. The chemical structures were determined using gas chromatography (GC), high‐performance gel permeation chromatography (HPGPC), Fourier‐transform infrared (FT‐IR) spectroscopy, and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The results indicated that OG1 was composed of rhamnose and little mannose (8.71%), the ratio of Rha: Gal: Xyl: Fuc in OG3 were 14:5.5:3:1. And their average molecular weights (Mw) were about 1.66 × 106 and 2.33 × 106 Da, respectively. OG2 was composed only of glucose (98.23%), which means it was glycogen. OG2 was consisted mainly of →4)‐ α‐D‐Glc‐(1→, with the branch chain every 6.5 glucose residues on average, which is →4,6)‐α‐D‐Glc‐(1→ and trace amount of α‐D‐Glc‐(1→ branched units. The Mw was 2.27 × 106 Da. It provides the bases for the bioactivity research. [ABSTRACT FROM AUTHOR]

The growth of Vibrio parahaemolyticus (V. parahaemolyticus) in oysters during postharvest storage increases the possibility of its infection in humans. In this work, to investigate the growth or survival profiles in different media, pathogenic V. parahaemolyticus in APW, Jinjiang oyster (JO, Crassostrea rivularis) slurry, and live JO were studied under different temperatures. All the strain populations were counted through our double-layer agar plate (DLAP) method. In APW, the pathogenic V. parahaemolyticus showed continuous growth under 15, 25, and 35°C, while a decline in behavior was displayed under 5°C. The similar survival trend of pathogenic V. parahaemolyticus in JO slurry and live JO was observed under 5, 25, and 35°C, except the delayed growth or decline profile compared to APW. Under 15°C, they displayed decline and growth profile in JO slurry and live JO, respectively. These results indicate the different sensitivity of pathogenic V. parahaemolyticus in these matrices to temperature variation. Furthermore, nonpathogenic V. parahaemolyticus displayed little difference in survival profiles when inoculated in live JO under corresponding temperatures. The results indicate that inhibition or promotion effect could be regulated under different storage temperature for both pathogenic and nonpathogenic strains. Besides, the DLAP method showed the obvious quickness and efficiency during the bacteria count. [ABSTRACT FROM AUTHOR]

Triploid oyster induction has been very successful. However, during field culture, a certain proportion of triploids apparently loses one set of chromosomes, 'reverting' to diploid-triploid mosaics. The revertants will lose their aquaculture advantages due to the recovery of reproductive ability. Mitotic chromosomes were observed in mosaics of Crassostrea gigas and Crassostrea Ariakensis to elucidate the cytogenetic mechanism of reversion. Most individuals showed a modal number of 30 in triploid cells and varying numbers of chromosomes in other cells. From all 15 mosaics of C. gigas and 16 mosaics of C. ariakensis individuals, high proportions of aneuploid cells with various numbers of chromosomes were observed. Most of the aneuploid cells were hypotriploid cells with 26-29 chromosomes. Notably, in 10 out of 15 C. gigas and 9 out of 16 C. ariakensis, some cells consisted of 20-26 well-spread chromosomes and 3-10 chromosome 'clumps'. Individuals with more chromosome clumps tended to have higher percentages of hypotriploid cells. The correlation between these two categories of cells was significant ( P<0.05) in C. gigas and highly significant ( P<0.01) in C. ariakensis. Thus, we conclude that some chromosomes are eliminated during mitotic divisions because they clump together and are thus unable to undergo normal segregation. [ABSTRACT FROM AUTHOR]

Reversion from triploids to diploids or heteroploid mosaics may make the revertants recover reproductive ability and lose their aquacultural advantages. Meiotic chromosomes in triploids and mosaics of Crassostrea gigas and Crassostrea ariakensis were studied. Pachytene spermatocytes showed incomplete trivalent formation, varying 64-72% in C. gigas and 62-69% in C. ariakensis. At metaphase I, trivalents, bivalents and univalents occurred in various combinations. Trivalents occurred in all spermatocytes, ranged 6-10 per spermatocyte and averaged 8.53-8.97 in C. gigas and 8.49-8.95 in C. ariakensis. Univalents and bivalents appeared in 59.2-72.1% of the spermatocytes in C. gigas, and ranged 0.77-1.39 and 1.01-1.51 per spermatocyte respectively. In C. ariakensis, they occurred in 57.5-81% of the spermatocytes, and ranged 0.9-1.32 and 1.03-1.35 respectively. The most common trivalent was formed by a bivalent with the third chromosome attaching to its side to form 'long-tail-cross' or 't' or 'frying-pan'-shaped configurations that constituted 65.7% and 59.9% of the trivalents in C. gigas and C. ariakensis respectively. Other kinds of trivalent associations included tandem chains (14.7%, 16.5%), closed circles or triangles (5.3%, 9.8%), convergent 'T' or 'Y' (5.8%, 7.4%) and unclassified configurations (8.5%, 6.4%). Diploid spermatocytes were not observed from mosaics, although they showed considerable proportions of 'diploid' cells in their gills. [ABSTRACT FROM AUTHOR]

Discusses the presence of rickettsia associated with lesions in the Crassostrea ariakensis that were sampled from Kaozhou Bay in Huidong, China. Histological examination results; Results of the light examination of affected tissue sections; Results of the electron microscopical examination of the digestive gland and mantle tissues; Description of lesions.

Clones from four partial genomic libraries of the Asian oyster Crassostrea ariakensis were screened to reveal 64 microsatellite-containing sequences. Polymerase chain reaction primers were designed for 34 of these loci. Reactions were optimized for 11 primer pairs and markers were evaluated in eight family crosses and one wild population from northern China. Zero to three null alleles per locus were identified in family crosses, and two of the 11 loci showed allele frequency deviations from Hardy–Weinberg equilibrium in the wild population. These markers have proven useful for genetic studies of C. ariakensis. [ABSTRACT FROM AUTHOR]