Scapharca Subcrenata Research Articles

Microbial community and interspecies interaction during grazing of ark shell bivalve (Scapharca subcrenata) in a full-scale bioremediation system of mariculture effluents

A novel biological approach using ark shell bivalves as potential species for remediation of effluents was studied to determine the microbial community interspecies interaction and nutrient cycling in a restoration system of mariculture effluents. A field study showed that Scapharca subcrenata was the main driver of the microbial community's interspecies-interaction (PERMANOVA, R = 0.0572, P = 0.005) in the treatment zone (TZ). Analysis of co-occurrence networks based on random matrix theory (RMT) indicated that the network's complexity parameters were enhanced in the TZ and disrupted in the control zone (CZ) due to eutrophic disturbances. Concurrently, the TZ was correlated with more profound network modifications (i.e., higher modularity, total nodes (n), cohesion, and proportion of positive links), suggesting that S. subcrenata influenced microbial interspecies interactions in the system. Similarly, the co-occurring networks of generalists Proteobacteria (OTU2037) at genus Anaerospora and Actinobacteria (OTU9660) at genus Candidatus aquiluna for anaerobic ammonia-oxidation (ANAMMOX) were highly significant in the TZ. The top-down and bottom-up forces of S. subcrenata influenced the removal efficiency of nitrogenous compounds by reducing 81.51% of nitrite (NO2−-N), 84.61% of total ammonium nitrogen (TAN) and 72.78% of nitrate (NO3−-N). Generally, the introduction of ark shell bivalve (S. subcrenata) to the system as a biofilter provides a very low-cost bioremediation technology that could be one of the best restorations and remediation tools for mariculture effluents.

Metabolic response of Scapharca subcrenata to heat stress using GC/MS-based metabolomics.

Marine mollusks are commonly subjected to heat stress. To evaluate the effects of heat stress on the physiological metabolism of the ark shell Scapharca subcrenata, clams were exposed to different high temperatures (24, 28 and 32 °C) for 72 h. The oxygen consumption and ammonia excretion rates were measured at 2, 12, 24, 48 and 72 h. The results indicated that the metabolic rates of the ark shell significantly increased with increasing heat stress, accompanied by mortalities in response to prolonged exposure. A metabolomics approach based on gas chromatography coupled with mass spectrometry was further applied to assess the changes of metabolites in the mantle of the ark shell at 32 °C. Moreover, multivariate and pathway analyses were conducted for the different metabolites. The results showed that the heat stress caused changes in energy metabolism, amino acid metabolism, osmotic regulation, carbohydrate metabolism and lipid metabolism through different metabolic pathways. These results are consistent with the significant changes of oxygen consumption rate and ammonia excretion rate. The present study contributes to the understanding of the impacts of heat stress on intertidal bivalves and elucidates the relationship between individual-level responses and underlying molecular metabolic dynamics.

The Effect of Bioturbation Activity of the Ark Clam Scapharca subcrenata on the Fluxes of Nutrient Exchange at the Sediment-Water Interface

Filter-feeding shellfish are common benthos and significantly affect the biogeochemical cycle in the shallow coastal ecosystems. Ark clam Scapharca subcrenata is one of the widely cultured bivalve species in many coastal areas owing to its tremendous economic value. However, there is little information regarding the effects of the bioturbation of S. subcrenata on the fluxes of nutrient exchange in the sediment-water interface (SWI). In this regard, S. subcrenata was sampled during October 2016 to determine the effects of its bioturbation activity on the nutrient exchange flux of the SWI. The results showed that the biological activity of S. subcrenata could increase the diffusion depth and the rate of the nutrients exchange in the sediments. The bioturbation of S. subcrenata could allow the nutrients to permeate into the surface sediments at 6–10 cm and increase the release rate of nutrients at the SWI. The releasing fluxes of DIN and PO 4 3− -P in the culture area were found to be around three times higher than that in the non-cultured region. The culture of S. subcrenata has been proved to be an important contributor to nutrient exchange across the SWI in the farming area of Haizhou Bay. Nutrients exchange in the SWI contributes a part of 86% DIN, 71% PO 4 3− -P and 18% SiO 3 2− -Si for the aquaculture farm.

Histochemical Distribution of Three Types of Enzymes and Mucous Cells in the Gill, Mantle and Hepatopancreas of the Ark Shell Scapharca subcrenata

The present study was aimed at evaluating the histochemical distribution of alkaline phosphatase (ALP), nonspecific esterase (NSE), peroxidase (POD) and various types of mucous cells in the gill, mantle and hepatopancreas of the ark shell Scapharca subcrenata. The ALP activity was found in the epithelial cells (EP) of the gill filament and the mantle as well as in the basal lamina of the glandular duct in the hepatopancreas. The staining intensity of ALP in the mantle and hepatopancreas was stronger than that in the gill. The NSE activity was detected in the EP in the gill filament, mantle and hepatopancreas, with the hepatopancreas showing a stronger intensity than the gill. The POD activity was located in the EP of the mantle and glandular duct of the hepatopancreas as well as in the connective tissue of the gill. The mantle showed stronger staining intensity of POD than the hepatopancreas. The Alcian blue (pH 2.5) periodic acid Schiff (AB-PAS) histochemical results revealed four types of mucous cells in the gill, mantle and hepatopancreas. Type III cells (nPAS+AB+) and type IV cells (aPAS+AB+) were observed in the gill, mantle and hepatopancreas. Type I cells (PAS+AB–) were not detected in the hepatopancreas but were distributed ubiquitously throughout the gill filament and mantle. Type II cells (PAS–AB+) were not detected in the gill but were distributed ubiquitously in the digestive ducts of the hepatopancreas.

Assessment of heavy metal bioaccumulation in food web of the coastal waters of Jiangsu Province, China, based on stable isotope values (δ13C and δ15N).

The coastal waters in Jiangsu Province have always been an important fishery base since ancient time. In recent years, with the development of the industry in coastal cities, heavy metal pollution is becoming serious in Jiangsu Province. However, the bioaccumulation of heavy metals in the coastal food web is still unclear. In this study, we collected samples (including macroalgae, bivalves, cephalopods, gastropods, crustaceans and fish) through fishery resources survey in the coastal waters of Jiangsu in May 2017 and quantified the main ways of the material circulation and energy flows by constructing the food web using stable carbon and nitrogen isotopes. In addition, the bioaccumulation patterns of eight elements (seven heavy metals and 1 metalloid) through the food chains were investigated. The results showed that there were two energy pathways in this offshore ecosystem: the planktonic food-chain and the benthic food-chain, with Scapharca subcrenata and Phalium strigatum as the primary consumers, respectively. The benthic food-chain was the dominant food chain in energy recycling. The mean concentration of heavy metals from high to low in orga-nisms were Zn, Cu, As, Cd, Cr, Pb, Ni and Hg. The highest concentrations of elements were found in bivalves and the lowest ones in fish. The concentration of As in most species, the levels of Cd in bivalves and Oratosquilla oratoria, the Cr in Coilia mystus and the Zn, Cu, Cr in Ostrea denselamellosa exceeded the proposed health advisory levels. Regarding the bioaccumulation, a decrease in the concentration levels of Zn, Cd and Ni were observed along the planktonic food-chain and a significant positive correlation between Hg and trophic position were found across the benthic food-chain. Other elements had no significant change.

Purification and characterization of antioxidant peptides from enzymatically hydrolyzed ark shell ( Scapharca subcrenata )

Abstract Information of bioactive peptides derived from ark shell is seldom reported. In this study, ark shell was hydrolyzed by pepsin with enzyme to substrate (E/S) ratios of 1:100 and 1:500 for 1–4 h. Ark shell hydrolysates (ASHs) were subjected to evaluate their antioxidant activities by free radical scavenging and oxygen radical absorbance capacity (ORAC) assays. Antioxidant peptides (P) were purified and identified as MCLDSCLL (P1) and HPLDSLCL (P2). P1 and P2 showed potent antioxidant activities with IC50 value of 19.47 ± 0.35 and 74.36 ± 0.54 μM, and glutathione (GSH), as positive control, showed 19.31 ± 0.36 μM against DPPH radical. P1 and P2 exhibited 678.36 ± 5.33 μM trolox equivalent (TE)/mM P1 and 778.86 ± 9.64 μM TE/mM P2 against ABTS+ radical scavenging, and ORAC values of 333.91 ± 26.05 μM TE/mM P1 and 209.81 ± 21.74 μM TE/mM P2. P1 and P2 also showed strong reducing power. In addition, P2 strongly inhibited copper-catalyzed human LDL oxidation.

Real-time quantitative isothermal detection of Ostreid herpesvirus-1 DNA in Scapharca subcrenata using recombinase polymerase amplification

Ostreid herpesvirus-1 (OsHV-1) is a well-known pathogen associated with high mortality rates in hatchery-reared larvae and juveniles of different bivalve species worldwide. Early, rapid and accurate diagnosis plays a fundamental role in disease prevention and control in aquaculture. Recombinase polymerase amplification (RPA) is a novel isothermal amplification method, which can amplify detectable amount of DNA at 37 °C–39 °C within 20 min. In the present study, two sets of specific primers and probes were designed for the real-time quantitative RPA (qRPA) detection of OsHV-1 DNA. The sensitivity and specificity of detection were evaluated by comparison with quantitative polymerase chain reaction (qPCR). The detection limit for qRPA assays was shown to be 5 copies DNA/reaction for the primer set ORF95, which was lower than the 100 copies required for the qPCR test. The optimal reaction temperature and time were 37 °C for 20 min, making this approach faster than qPCR. This is the first study to apply qPCR and qRPA methods to detect OsHV-1 in Scapharca subcrenata. The percentage of viral load sample detected by the two methods was 22% and the correlation of the two virus quantitative results was 0.8. Therefore, qRPA assays is sensitive, fast, and high-temperature independent relative to qPCR and is suitable for critical clinical diagnostics use and rapid field analysis in resource-limited settings.

남해안 강진만에서 생산되는 굴 (Crassostrea gigas), 바지락 (Ruditapes philippinarum), 및 새꼬막 (Scapharca subcrenata) 의 위생학적 평가

남해안 강진만에서 생산되는 굴 (Crassostrea gigas), 바지락 (Ruditapes philippinarum), 및 새꼬막 (Scapharca subcrenata) 의 위생학적 평가

Application of Ecological Restoration Project in Port Construction

Ecological restoration project in the domestic port construction is from research to the application stage. Tianjin Port by creating artificial beach as a habitat, supplemented by proliferation and release, making the East Bay demonstration area of the artificial coastline ecological rapid restoration. The biomass of the main and economic types increased by 103.1%, and the oyster-barnacle ecosystem was reconstructed in the rocky coastal zone around the breakwater. In the intertidal tidal flats of the breakwater, the ecosystems composed of Cyclina sinensis— Sinonovacula constricta—Mactra veneriformis—Scapharca subcrenata were reconstructed. In the artificial beach, reconstructed by the Ruditapes philippinarum—Mactra veneriformis—Scapharca subcrenata ecological system.

Elemental techniques for automated size sorting system considering problems and status of sorting process of ark shell (Scapharca subcrenata)

Elemental techniques for automated size sorting system considering problems and status of sorting process of ark shell (Scapharca subcrenata)

QPCR analysis of bivalve larvae feeding preferences when grazing on mixed microalgal diets.

Characterization of the feeding preferences of bivalve larvae would help improving the bivalve aquaculture and hatchery by providing appropriate microalgal diets. However, inaccurate and laborious identification and counting of microalgal species have challenged the selective feeding of bivalves. In the present study, we developed a highly specific and sensitive assay using quantitative polymerase chain reaction (qPCR) to assess the selective feeding of bivalve larvae based on species-specific primers targeting to microalgal 18S rDNA sequences. The assay exhibited good specificity. The detection limits of the qPCR assay were 769, 71, 781 and 21 18S rDNA copies for Chaetoceros calcitrans, Isochrysis galbana, Platymonas helgolandica and Nannochloropsis oculata, respectively. Using such assay, we found that C. calcitrans and I. galbana were preferentially ingested, whereas N. oculata was preferentially rejected in biodeposits of four bivalve species, Tegillarca gransa, Cyclina sinensis, Scapharca subcrenata and Sinonovacula constricta. Furthermore, our growth experiments revealed that C. calcitrans and I. galbana could significantly promote the shell growth, whereas feeding of N. oculata resulted in poorer growth of four bivalve species. These data indicated that qPCR might be useful in screening of efficient and reliable microalgal species for each bivalve species, leading to improved bivalve aquaculture and hatchery.

Comparative and evolutionary analysis of an adapter molecule MyD88 in invertebrate metazoans

The myeloid differentiation factor 88 (MyD88) is an essential adapter in Toll-like receptor (TLR) signalling pathways, with TLR the first pattern-recognition receptor (PRR) that was discovered in Drosophila. In the present study, a MyD88 gene was identified and characterized from a commercially important shellfish, Scapharca subcrenata, including a DEATH domain and TIR domain conserved within other molluscs. Furthermore, comparative genomic evidence revealed that MyD88 was of different lengths and contained quantitative exon and intron regions, which might be involved in specific mechanisms. To further explore the phylogenetic relationships of invertebrate metazoan MyD88, we applied MrBayes and PhyML software to construct phylogenetic trees using Bayesian and maximum likelihood approaches, respectively, which suggested that the MyD88 of Arthropoda was closely related to lower invertebrates, in contrast to morphological taxonomy. Finally, we investigated the evolutionary patterns and location of positive selection sites (PSSs) in the MyD88 gene from Arthropoda, Mollusca and Insecta using PAML software with the maximum likelihood method. The data showed that positive selection sites were detected in these groups, and partial sites were located in the TIR domain but were not found in the DEATH domain. To summarize, in this study, we report on the diversification of MyD88 in invertebrate metazoans, the specific evolutionary position of Arthropoda MyD88, and the positive selection pressures on MyD88 of Arthropoda, Mollusca and Insecta. These results are a valuable contribution to understand and clarify the evolutionary pattern of TLR/MyD88 signalling pathways in invertebrate and vertebrate taxa.

Bioaccumulation of heavy metals and health risk assessment in three benthic bivalves along the coast of Laizhou Bay, China

This study investigated the tissue- and species-specific bioaccumulation of heavy metals (Cr, Cu, Hg, Zn, As, Cd, and Pb) in three benthic bivalves (the ark shell, Scapharca subcrenata; the surf clam, Mactra veneriformis; and the Manila clam, Ruditapes philippinarum) collected from the coast of Laizhou Bay in the Bohai Sea. The results demonstrated that the visceral masses of the bivalves tended to accumulate heavy metals more efficiently than their muscles. The capacities of the bivalves to bioaccumulate metals followed a similar order: Cd>Hg>Zn=As>Cu>Cr=Pb. The conditions of metal contamination in the bivalves tended to be worse along the eastern coast than in other regions. Overall, the Manila clam was more severely contaminated by heavy metals than the surf clam and ark shell. Judging by the hazard quotients (HQ) of the metals in the muscles of the bivalves, the greatest hazard risk to human health comes primarily from As.

Development and characterization of 37 SNP markers in the ark shell Scapharca subcrenata using RAD sequencing and high resolution melting analysis

The ark shell Scapharca subcrenata, an important fishery resource in Asian countries, has been suffering from severe population decline in recent years. To facilitate genetic conservation studies, novel single nucleotide polymorphisms (SNPs) markers were developed using next generation sequencing for this species, which yielded a total of 781,860 putative SNPs. To validate these markers, 96 SNP genotyping assays were designed to characterize polymorphisms using high resolution melting (HRM) analysis in 32 individuals from a wild population. As a result, 37 SNPs showed polymorphisms with MAF ranging from 0.0313 to 0.4844. The observed heterozygosity ranged from 0 to 0.8333, while the expected heterozygosity varied from 0.0605 to 0.4995. After the Bonferroni correction, 5 of the 37 loci showed significant departure from Hardy–Weinberg equilibrium. These novel SNP markers will be useful for future investigation of population structure and conservation genetics of the ark shell S. subcrenata.

Habitat suitability of Scapharca subcrenata (Lischke) in the shallow water of the Xiaoheishan Island

The habitat suitability index (HSI) model was used to identify potential sites for sustainable restoration of ark shell, Scapharca subcrenata (Lischke), in the shallow water of Xiaoheishan Island, using a geographic information system framework. The seven input variables of the HSI model were sediment composition, water temperature, salinity, dissolved oxygen, water depth, pH, and ammonia. A non-linear suitability function for each variable factor was used to transform the value into a normalized quality index ranging from 0 (nonsuitability) to 1 (best suitability). In present study, the analysis of habitat suitability was conducted for four seasons respectively. The majority of the study area has a high HSI value (>0.6) year round, which implies a strong suitability for restoration, with the optimal habitat located on the eastern side of the island. Correspondence analysis indicated that water temperature was the main factor causing seasonal variation, while sediment composition and water depth were the two major reasons for the differences in sites. The results of this work could provide support for restoration decision making through identification of potential sites for sustainable establishment of S. subcrenata.

전남 여자만 해수 및 새꼬막(Scapharca subcrenata)의 세균학적 위생 평가

전남 여자만 해수 및 새꼬막(Scapharca subcrenata)의 세균학적 위생 평가

Ultrastructural Studies on Oocyte Development and Vitellogenesis associated with Follicle Cells in Female Scapharca subcrenata (Pelecypoda: Arcidae) in Western Korea.

Ultrastructural studies on oocyte development and vitellogenesis in oocytes, and the functions of follicle cells during oogenesis and oocyte degeneration were investigated to clarifyb the reproductive mechanism on vitellogenesis of Scapharca subcrenata using electron microscope observations. In this study, vitellogenesis during oogenesis in the oocytes occured by way of autosynthesis and heterosynthesis. Of two processes of vitellogenesis during oogenesis, the process of endogenous autosynthesis involved the combined activity of the Golgi complex, mitochondria and rough endoplasmic reticulum. However, the process of exogenous heterosynthesis involved endocytotic incorporation of extraovarian precursors at the basal region of the oolema of the early vitellogenic oocytes before the formation of the vitelline coat. In this study, follicle cells, which attached to the previtellogenic and vitellogenic oocytes, were easily found. In particular, the follicle cells were involved in the development of previtellogenic oocytes by the supply of nutrients, and vitellogenesis in the early and late vitellogenic oocytes by endocytosis of yolk precursors. Based on observations of follicle cells attached to degenerating oocytes after spawning, follicles of this species are involved in lysosomal induction of oocyte degeneration for the resorption phagosomes (phagolysosomes) in the cytoplasm for nutrient storage, as seen in other bivalves. In this study, the functions of follicle cells can accumulate reserves of lipid granules and glycogen particles for vitellogenesis from degenerating oocytes after spawning.

Effect of Acute Temperature Change on Antioxidant Enzyme Activities and Lipid Peroxidation in the Ark ShellScapharca subcrenata(Lischke, 1869)

The present study investigated whether an acute temperature change affected hemolymph antioxidant enzyme activities and lipid peroxidation in ark shell Scapharca subcrenata transferred from 22°C to 17°C, 27°C, and 32°C for 72 h and then transferred back quickly to 22°C for a 6-h recovery period. Superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities and malondialdehyde (MDA) contents [in cell-free hemolymph (CFH) and hemocyte lysate (HL)] were chosen as biomarkers of acute temperature stress. The results demonstrated that CFH and HL SOD activities decreased significantly (P < 0.05) after ark shells were exposed to 32°C for 72 h and returned to normal temperature. Glutathione peroxidase activity in CFH of ark shells exposed to 32°C increased significantly (P < 0.01) at 12 h, but then decreased significantly (P < 0.01) at the end of the recovery period. Malondialdehyde contents in the CFHandHL of stressed ark shells, regardless of temperature (17°C, 27°C, or 32°C), were lowest at 1 h of the recovery period, and recovered completely by the end of the experiment. In contrast, no difference was observed in CFH or HLMDA contents between the 17°C and 27°C groups. In conclusion, S. subcrenata had high tolerance to an acute decrease and increase in seawater temperature, but oxidative stress in ark shell hemolymph increased significantly with temperature and time, such as 32°C and greater than 72 h.

P-glycoprotein and its inducible expression in three bivalve species after exposure to Prorocentrum lima

P-glycoprotein (P-gp or ABCB1) belongs to the family of ATP-binding cassette (ABC) transporters responsible for multixenobiotic resistance (MXR) in aquatic organisms. To provide more information of P-gp in shellfish, in this study, complete cDNA of P-gp in three bivalve species including Ruditapes philippinarum, Scapharca subcrenata and Tegillarca granosa were cloned and its expressions in gill, digestive gland, adductor muscle and mantle of the three bivalves were detected after exposure to Prorocentrum lima, a toxogenic dinoflagellate. The complete sequences of R. philippinarum, S. subcrenata and T. granosa P-gp showed high homology with MDR/P-gp/ABCB proteins from other species, having a typical sequence organization as full transporters from the ABCB family. Phylogenetic analyses revealed that the amino acid sequences of P-gp from S. subcrenata and T. granosa had a closest relationship, forming an independent branch, then grouping into the other branch with Mytilus californianus, Mytilus galloprovincialis and Crassostrea gigas. However, P-gp sequences from R. philippinarum were more similar to the homologs from the more distantly related Aplysia californica than to homologs from S. subcrenata and T. granosa, suggesting that bivalves P-gp might have different paralogs. P-glycoprotein expressed in all detected tissues but there were large differences between them. After exposure to P. lima, the expression of P-gp changed in the four tissues in varying degrees within the same species and between different species, but the changes in mRNA and protein level were not always synchronous.

Microplastics in commercial bivalves from China

We investigated microplastic pollution in 9 commercial bivalves from a fishery market in China. Multiple types of microplastics, including fibers, fragments and pellets, occurred in the tissue of all bivalves. The number of total microplastics varied from 2.1 to 10.5 items/g and from 4.3 to 57.2 items/individual for bivalves. Scapharca subcrenata contained on average 10.5 items/g and exhibited the highest levels of microplastics by weight. Fibers were the most common microplastics and consisted of more than half of the total microplastics in each of the 8 species. In Alectryonella plicatula, pellets accounted for 60% of the total microplastics. The most common size class was less than 250 μm and accounted for 33–84% of the total microplastics calculated by species. Our results suggest that microplastic pollution was widespread and exhibited a relatively high level in commercial bivalves from China. More intensive investigations on microplastics should be conducted in seafood.