Chlamys Nobilis Research Articles

Srebp-1 bridges gonad development and lipid accumulation by regulating lipogenesis in noble scallop Chlamys nobilis

In bivalve, development of female gonad is accompanied with accumulating lipids which provided energy resource for non-feeding larvae development. As the major transcriptional regulators of lipid metabolism, Srebps play pivotal role in lipid homeostasis during oogenesis. However, little work was conducted on Srebps function in bivalves. The noble scallop Chlamys nobilis accumulated large amount of lipids in its gonad during oogenesis. Here, we identified a single Srebp gene (named Srebp-1) with a high similarity to human Srebp-1c. Disrupting Srebp-1 with Betulin (inhibiting the maturation of Srebp protein) repressed expression of lipogenic genes and de novo lipogenesis, and resulted in reduction of gonad index and lipid deposition, suggesting a crucial role of Srebp-1 for gonad development and lipid synthesis in female gonad. Additionally, scallops with Srebp-1 disruption released fewer eggs with a reduction in their lipid content and D-larvae formation, revealing an impair of fecundity caused by Srebp-1 disruption. Cold exposure stimulated lipid accumulation which required Srebp-1 to regulate de novo lipogenesis and lipid uptake, providing a crosstalk of Srebp-1 activity and environmental variation on lipid accumulation in noble scallop. Thus, our study identified Srebp-1 as a central regulator coordinating the lipid synthesis and accumulation with gonad development in noble scallop.

Effects of chronic cold stress on tissue structure, antioxidant response, and key gene expression in the warm-water bivalve Chlamys nobilis

As ectothermic invertebrates, mollusks are regarded as good environmental indicator species for determining the adverse effects of climate change on marine organisms. In the present study, the effects of cold stress on the tissue structure, antioxidant activity, and expression levels of genes were evaluated in the warm-water noble scallop Chlamys nobilis by simulating natural seawater cooled down during winter from 17 °C to 14 °C, 12 °C, 10 °C, and 9 °C. Firstly, the gill was severely damaged at 10 °C and 9 °C, indicating that it could be used as a visually indicative organ for monitoring cold stress. The methylenedioxyamphetamine (MDA) content significantly increased with the temperatures decreasing, meanwhile, the antioxidant enzyme activities superoxide dismutase (SOD) and catalase (CAT) showed a similar pattern, suggesting that the scallop made a positive response. More importantly, 6179 genes related to low temperatures were constructed in a module-gene clustering heat map including 10 modules. Furthermore, three gene modules about membrane lipid metabolism, amino acid metabolism, and molecular defense were identified. Finally, six key genes were verified, and HEATR1, HSP70B2, PI3K, and ATP6V1B were significantly upregulated, while WNT6 and SHMT were significantly downregulated under cold stress. This study provides a dynamic demonstration of the major gene pathways' response to various low-temperature stresses from a transcriptomic perspective. The findings shed light on how warm-water bivalves can tolerate cold stress and can help in breeding new strains of aquatic organisms with low-temperature resistance.

Functional, physicochemical, and rheological properties of the spray drying particles prepared from the noble scallop (Chlamys nobilis) mantle protein‐pectin hydrated mixtures

SummaryThe present study aimed to comparatively analyse the functional properties of the spray drying particles prepared from the noble scallop (Chlamys nobilis) mantle protein‐pectin hydrated mixtures. And the microstructural characteristics of the particles were assessed by Fourier transform infrared, scanning electronic microscopy, and SDS‐PAGE to detect critical changes. The results showed that the solubility of enzymatically extracted protein was significantly improved by spray drying after pectin hydration (AP‐LMP and AP‐HMP), from 76.77% (AP) to 97.87% (AP‐LMP) and 97.13% (AP‐HMP), respectively. And the spray drying water‐extracted protein (HP) after pectin hydration (HP‐LMP and HP ‐HMP) exhibited a greater emulsifying property, from 103.10 m2/g (HP) to 145.55 ± 0.92 m2/g (HP‐LMP) and 200.29 ± 1.16 m2/g (HP‐HMP). The spray drying after pectin hydration had successfully enhanced emulsifying and rheological properties when compared with AP and HP. The results of SDS‐PAGE showed more protein participated in the formation of macromolecule and FT‐IR spectra demonstrated the formation of protein‐pectin spray drying particles facilitated not only by electrostatic interactions but also by covalent binding via Maillard reaction, made a closely compatible protein structure verified by the improvement of fluorescence intensity. This work is expected to provide a theoretical basic data for the development and application of scallop mantle extracted proteins.

Tetrodotoxin Detection in Japanese Bivalves: Toxification Status of Scallops.

Tetrodotoxin (TTX), or pufferfish toxin, has been frequently detected in edible bivalves around the world during the last decade and is problematic in food hygiene and safety. It was reported recently that highly concentrated TTX was detected in the midgut gland of the akazara scallop Chlamys (Azumapecten) farreri subsp. akazara collected in coastal areas of the northern Japanese archipelago. The toxification of the bivalve was likely to involve the larvae of the flatworm, Planocera multitentaculata. However, the overall status of bivalve TTX toxification has not been elucidated. In this study, 14 species/subspecies of bivalves from various Japanese waters were subjected to LC-MS/MS analysis to reveal TTX toxification state, demonstrating that the Pectinidae, including C. farreri akazara, Chlamys farreri nipponensis, Chlamys (Mimachlamys) nobilis, and Mizuhopecten yessoensis, accumulated TTX in their midgut gland. Many individuals of C. farreri akazara and C. farreri nipponensis were found with high concentrations of TTX, while C. nobilis and M. yessoensis exhibited low concentrations. The extent of TTX accumulation in C. farreri akazara and C. farreri nipponensis varied widely by region and season. Curiously, no other bivalve species investigated in this study showed evidence of TTX. These results suggest that monitoring for TTX, like other shellfish toxins, is necessary to ensure that pectinid bivalves are a safe food resource.

Circulatory and Metabolic Physiology Disorder in Different Organs of the Subtropical Scallop Species Chlamys nobilis Under Thermal and Hypoxia Stress, Revealed by Doppler Ultrasonography Technique

Extremely high temperature and hypoxia are mounting problems affecting the world’s coastal waters under the global warming environment, with severe consequences for marine life. Scallop is one of the most fragile species to hypoxia stress for their high respiration rate and lack of self-protection ability such as long-time shell closing. Circulatory physiology rhythm is sensitive to environmental stress and is an important means for shellfish to quickly respond to environmental stress. Therefore, monitoring the circulatory physiology indexes of Chlamys nobilis under hypoxia and high temperature stress is helpful to quickly diagnose its stress state and reveal the response process of circulatory system to the stress. In this study, using real-time Doppler ultrasonography technique, we continuously monitored the circulatory physiological indexes [heart rate (HR), blood flow volume (FV), blood velocity (PS and ED), resistance index (RI) and S/D ratio) of the scallop organs (gill, mantle and adductor muscle) under hypoxia (mild 4 mg/L DO, moderate 3 mg/L DO and severe 2 mg/L DO)] and fluctuating high temperature stress (29-31°C). Important metabolic function indexes [adenosine triphosphate (ATP), pyruvate kinase (PK) and cytochrome C oxidase (COX)] of various tissues were measured simultaneously. The results show that scallops are very sensitive to the changes of temperature and dissolved oxygen. Both high temperature and hypoxia will increase the HR, and severe hypoxia will bring greater load to the heart of the scallop. Hypoxia stress mainly caused the changes of PS, and the RI and S/D of the gill gradually increased. At 2mg/L DO level, the total blood flow of the mantle and adductor muscle decreased, but the blood flow supply in the gill was stable. The scallop is very sensitive to the change of high temperature and can make adjustments immediately. High temperature increased blood flow in various organs and preferentially supplied to the gill. The RI and S/D of branchial vessels under high temperature were lower than those under hypoxia. The ATP content of the mantle was continuous accumulated under high temperature and was significantly higher than that of the gill and adductor muscle, indicating the specificity of tissue metabolism. The overall circulatory physiological indexes of the gill showed a more positive response to the stress environment than the mantle and adductor muscle. All the results proved that the gill has the best resistance to the hypoxia and high temperature stress. Our study revealed the circulatory physiology regulation mechanism of the noble scallop C. nobilis under environmental stress, and provide effective data and technique supports for the timely diagnose of stress condition of the species, so as to formulate necessary handling strategies for the scallop farm.

Intraspecific hybridization as a mitigation strategy of ocean acidification in marine bivalve noble scallop Chlamys nobilis

The driving factors of climate change, especially ocean acidification (OA), have many detrimental impacts on marine bivalves. Hybridization is one of the important methods to improve environmental tolerance of animals and plants. In this study, we explored the feasibility of intraspecific hybridization as an OA mitigation strategy in noble scallop Chlamys nobilis (ecologically and economically important bivalve species). The results of this study revealed that exposure of C. nobilis to OA condition significantly reduced the hatching rate, survival rate, growth rate (shell height, shell length, shell width and shell weight), and total carotenoid content (TCC), as well as increased the deformity rate of C. nobilis larvae. Interestingly, under both ambient water and OA condition, the intraspecific hybridization of C. nobilis exhibited heterosis in terms of hatching rate, survival rate and growth rate (excepted for growth in shell length under OA). Transcriptome sequencing of C. nobilis (inbreed and hybrid under ambient and OA conditions) identified four main differentially expressed genes involved in signal transduction, biological process maintenances, nucleic acid binding and post-translational modification. In addition, the expression of these four genes in hybrid C. nobilis was significantly higher than that in inbreed C. nobilis. In conclusion, hybrid C. nobilis showed heterosis in growth rate and survival rate under both ambient water and acidified seawater condition, which may be the result of enhanced expression of genes related to signal transduction, DNA replication and post-translational modification.

Characterization of the CnMnSOD in response to lower temperature stress in noble scallop Chlamys nobilis with different carotenoids content

Manganese-superoxide dismutases (MnSODs) play vital roles in immune response and maintaining cellular physiology. In this study, a novel MnSOD (CnMnSOD) gene from noble scallop Chlamys nobilis was first cloned. The full-length cDNA sequence of CnMnSOD contains a 681 bp ORF with 226 amino acids and includes two highly conserved domains, a SOD Fe-N domain and a SOD Fe-C domain. Multiple sequence alignment and phylogenetic analysis showed CnMnSOD was highly conserved to other mollusks. Tissue expression analysis showed CnMnSOD had a significant difference between golden and brown scallops. The transcript level of CnMnSOD in blood, mantle and gill of golden and brown scallops was all significant up-regulated (p < 0.05) under lower temperature stress, and a more interesting finding was that golden scallops had a significantly higher expression levels in mantle and gill (p < 0.05) than those of brown scallops under lower temperature stress. Furthermore, analysis of variance showed the genetic and temperature stress all had significant effects on the expression level of CnMnSOD, and the interaction between them was also significant (p < 0.05). Collectively, these results indicated that CnMnSOD and carotenoids play important roles in the antioxidant system defence against the lower temperature stress, and the carotenoids in scallop may enhance the resistance by up-regulating genes related to innate immunity. These results will deepen our understanding to innate immune response of scallop under low-temperature stress.

Dietary exposure assessment of paralytic shellfish toxins through shellfish consumption in Shenzhen population, China.

Paralytic shellfish toxins (PSTs) produced by certain marine dinoflagellates accumulate in filter-feeding marine bivalves. We used LC-MS/MS to detect and quantify 13 PSTs in 188 shellfish samples of 14 species collected from Shenzhen city's Buji seafood wholesale market from March 2019 to February 2020. Twenty-six of 188 shellfish samples (13.8%) were PSTs detectable. Within 14 species, 10 out of 34 noble clam Chlamys nobilis samples contain detectable PSTs with the highest detection rate 29.4%. Seven out of 17 samples from Nan'ao island contained detectable PSTs with the highest detection rate 41.2% among 11 origins. Samples containing PSTs were concentrated in spring and winter, with the highest levels in March>December>January. Among PSTs detected, C1 was dominant. Acute dietary exposure assessment for Shenzhen residents were based on mean adult body weight, 99th percentile daily shellfish consumption of Shenzhen food consumption survey 2008 and maximum PSTs concentration for each shellfish species. The outcome for Chlamys nobilis was 2.4~3.7-fold higher than recommended ARfDs. Mean PSTs concentration, P99, and mean shellfish consumption were used to assess chronic dietary exposure. The results were lower than recommended ARfDs. In conclusion, residents in Shenzhen are at risk for acute PSTs poisoning, while relatively safe from chronic PSTs exposure.

Effects of single‐species microalgae diet on accumulation of lipid and carotenoid and expression of lipid‐related genes in Nan'ao Golden ScallopChlamys nobilis

Nan'ao Golden Scallop, Chlamys nobilis, is an important scallop species in aquaculture and is rich in lipids and carotenoid. Previous studies have shown that microalgae diet has a significant effect on the accumulation of total lipid content (TLC) and total carotenoid content (TCC) in bivalves. However, the effects of single-species microalgae diet on accumulation of TLC and TCC at molecular level are unclear. In this study, we used C. nobilis as a bivalve animal model to assess the effects of single-species microalgae diet (Tetraselmis subcordiformis, Dicrateria zhanjiangensis and Chaetoceros mulleri) on the accumulation of lipids and carotenoids, and the expression of stearoyl-CoA desaturase (SCD) and scavenger receptor class B-like-3 (SRB-like-3) genes in C. nobilis. The results of this study indicated that high lipid microalgae diet promoted the accumulation of TCC in C. nobilis tissues. The expression of SCD and SRB-like-3 genes was highly affected by the lipid composition of diet, in which high expression of SCD and SRB-like-3 genes was correlated with low C16:1n-9 and/or C18:1n-9t and/or C16:1/C16:0 and/or C18:1/C18:0. In intestine and adductor muscle, the expression of SCD gene was positively correlated with accumulation of TCC, TLC and fatty acid content, suggesting that SCD gene may indirectly promote the accumulation of TCC (lipid soluble) by promoting lipid accumulation. For SRB-like-3 gene, the high expression of SRB-like-3 was only correlated to the high TCC in intestine, suggesting that SRB-like-3 may be a candidate gene for carotenoid absorption in C. nobilis and has nothing to do with the transport or accumulation of carotenoid. The findings of this study are of great significance for further understanding how microalgae diet affects the accumulation of TCC and TLC, and the expression of lipid-related genes in bivalves.

A Significant Genetic Admixture in Farmed Populations of the Noble Scallop Chlamys nobilis Revealed by Microsatellite DNA Analysis in Southern China

The noble scallop, Chlamys nobilis, is an important bivalve mollusk with high commercial value and is usually farmed in the waters of southern China. To date, very little is known about the genetic diversity and population structure of C. nobilis. In this study, 10 microsatellite loci of four farmed C. nobilis populations were compared with one another and compared wild population in southern China. A total of 83 alleles were found. Surprisingly, the level of genetic diversity of the farmed C. nobilis populations was higher than that of the wild population. Although the population genetic of wild population was completely in the Hardy–Weinberg equilibrium, due to heterozygote deficiency, significant deviations from the Hardy–Weinberg equilibrium were found in all farmed populations, suggesting a genetic admixture caused by the mixing of seeds from various hatcheries. The Fst and AMOVA values showed significant genetic differences between wild and farmed populations. The Bayesian assignment also confirmed that genetic admixture was significant and widespread in artificial breeding of C. nobilis. Furthermore, the UPGMA tree topology and PCA demonstrated that the genetic diversity of wild population can be clearly distinguished from farmed populations. In a nutshell, the findings of this study not only fill the knowledge gaps in genetic diversity of wild and farmed C. nobilis populations, but also serve as a guide for maintaining the genetic diversity of C. nobilis in both farmed and wild populations.

Characterization of a novel catalase gene and its response to low temperature stress in noble scallop Chlamys nobilis with different total carotenoids content

Antioxidant system plays important roles in organisms under environmental stress by eliminating hydrogen peroxide. Catalase is an indispensable antioxidant protein that is essential for maintaining the redox balance of innate immune system. In this study, a novel catalase gene was first cloned from noble scallop Chlamys nobilis (named as CnCAT), and then its potential roles in respond to low temperature stress were investigated using golden (rich in carotenoids) and brown (less in carotenoids) C. nobilis. The CnCAT contains an ORF of 1569 bp encoding 522 amino acids. Phylogenetic tree analysis of CnCAT showed it had a higher identity with other molluscs. The distribution analysis indicated that the highest and the lowest expression level of CnCAT were found in gill and adductor respectively. Under low temperature stress, CnCAT expression level and CAT activity were significantly up-regulated, suggesting they play important roles in defence against the low temperature stress. In addition, the expression levels of CnCAT and CAT in golden scallops were significantly higher than those of brown scallops under low temperature stress, suggesting that the high carotenoid levels in the golden scallops may strengthen their toleration to low temperature stress. Collectively, these results indicated that CnCAT plays vital roles in the antioxidant system, and carotenoids in golden scallops may enhance their resistance to low temperature stress. These results will provide us a better understand to the immune response of scallops under low temperature stress.

Characterization of a novel cathepsin D and its immunity response in noble scallop Chlamys nobilis with different total carotenoids content

Cathepsin D is a soluble lysosomal aspartic proteinase of the pepsin superfamily that plays a crucial role in immune response. In this study, a novel cathepsin D of noble scallop Chlamys nobilis (named as CnCD) was cloned and its immune response to three different immunostimulants, including polyinosinic polycytidylic acid, lipo-polysaccharide and Vibrio parahaemolyticus, was investigated in golden scallops and brown scallops of C. nobilis with different carotenoids content. The full-length cDNA of CnCD is 1844 bp, containing a 63-bp 5′ terminal untranslated region (5′-UTR), a 1212-bp ORF encoding 403 amino acids and a 569-bp 3′-UTR. The predicted protein sequence of CnCD is composed of a signal peptide, a propeptide domain and a mature domain, and has a conserved bilobal structure. Phylogenetic analysis showed the CnCD was clustered into invertebrate group, and especially close to mollusc. Tissue distribution analysis of CnCD showed it was widely distributed in all tested tissues with higher levels in intestine, haemocytes and hepatopancreas. After immunostimulants challenged, CnCD transcripts were significantly up-regulated compared with the control group, indicating the CnCD plays important roles in immune response. Furthermore, the expression levels of CnCD in golden scallops were significantly higher than that of brown ones at most time points, suggesting carotenoids in golden scallops are important in promoting the immune response against pathogens. These results suggested that CnCD plays important roles in the immune defence against pathogens and the carotenoids can enhance the immune ability by up-regulating immune-related genes in noble scallop.

Effects of the Maillard reaction on the epitopes and immunoreactivity of tropomyosin, a major allergen in Chlamys nobilis.

Scallop (Chlamys nobilis) causes an IgE-mediated food allergy; however, studies of the allergens in its musculus are not sufficiently comprehensive. In this context, the target protein was purified from scallops and confirmed to be the major allergen tropomyosin (TM) using proteomic technology and serological testing. Subsequently, seven potential IgE epitopes of TM were obtained using phage display technology with IgE enrichment from the serum of scallop-sensitized patients and identified via inhibition enzyme-linked immunosorbent assays. A method for the Maillard reaction of TM and xylose was established, and Maillard-reacted TM (MR-TM) showed significantly decreased immunobinding activity and CD63 and CD203c expression in basophils compared with TM. Furthermore, shotgun proteomics analysis showed that eleven specific amino acids (K12, R15, K28, K76, R125, R127, K128, R133, R140, K146, and K189) of the six IgE epitopes of TM were modified after the Maillard reaction. Overall, the immunoactivity of MR-TM was reduced, which provides a theoretical reference for the development of hypoallergenic foods.

Differential responses of a pi-class glutathione S-transferase (CnGSTp) expression and antioxidant status between golden and brown noble scallops under pathogenic stress

Glutathione S-transferases (GSTs) play important roles in immunity by protecting organisms against the damage of reactive oxygen species (ROS). In this study, a pi-class GST cDNA sequence was first cloned from noble scallop Chlamys nobilis (named CnGSTp). The full length cDNA of CnGSTp was 922 bp, encoding a cytosolic protein of 202 amino acids residues, with predicted molecular masses of 23.1 kDa. Then an acute Vibrio Parahaemolyticus challenge experiment was conducted by using the Golden and Brown noble scallops with different total carotenoids content (TCC), and CnGSTp expression level, TCC and ROS level was separately determined. The results showed that ROS and CnGSTp expression levels were significantly up-regulate under Vibrio Parahaemolyticus challenge than the control group (P < 0.05). The Golden scallops showed significantly higher CnGSTp expression level and lower ROS level in hemocytes than the Brown ones (P < 0.05). Moreover, there is a significantly positive correlation between TCC and ROS in the Golden scallops. The present results revealed that CnGSTp plays important roles in immune response and carotenoids play assistant roles in antioxidant defense system under pathogenic stress in the noble scallop.

A novel carotenoids-producing marine bacterium from noble scallop Chlamys nobilis and antioxidant activities of its carotenoid compositions

Marine bacteria produce many bioactive compounds, including carotenoids. However, the quality of bacterium carotenoids is relatively unknown. Therefore, in this study, a novel carotenoids-producing bacterium Brevundimonas scallop Zheng & Liu was isolated from Chlamys nobilis. The genome of the isolate was analyzed, carotenoid compounds were screened using HPLC-MS and the carotenoid production in B. scallop was monitored. The results revealed that the genome of B. scallop contained a carotenoid synthesis gene cluster, which involved in astaxanthin and hydroxy-astaxanthin biosynthesis. The 2,2′-dihydroxy-astaxanthin was the major carotenoid produced by B. scallop. The optimum culture condition for the highest carotenoids production (1303.62 ± 61.06 µg/g dry cells) for B. scallop was at temperature and salinity of 20 °C and 3% salt, respectively, in 10 g/L glucose as carbon source. The results showed the B. scallop is a new carotenoids resource in marine bivalve, which has an excellent antioxidative activity and potential industrial use.

Comparison of Gut Microbiota Between Golden and Brown Noble Scallop Chlamys nobilis and Its Association With Carotenoids.

Many marine bivalves are regarded as healthy foods due to their high carotenoid content. Only plants and microorganisms have natural carotenoids biosynthesis ability, hence, animals such as bivalves must obtain carotenoids from their diets. Due to the filter-feeding behavior of bivalves, they have high diversity of gut microbes. However, the relationship between gut microbes and carotenoids has not been explored in mollusks. In the present study, the interaction between gut microbes and carotenoids in two polymorphic noble scallop Chlamys nobilis, golden scallops (designated GG) and brown scallops (designated BW), were studied. The gut of GG and BW showed statistically different bacteria communities. Results from 16S rRNA gene sequencing and qPCR analysis revealed that the gut of GG had significantly higher relative abundance of carotenoids-producing bacteria Brevundimonas, compared with BW. Moreover, HPLC-MS analysis showed that isolate Brevundimonas could produce astaxanthin. The current findings are very useful as they could form the basis for future studies in determining the relationship between gut microbiota and carotenoids absorption in bivalves.

Differential responses to low salinity on gene expression, physiological and biochemical indexes between the golden and brown noble scallopsChlamys nobilis

Low salinity is one of important environmental factors which often led to mass mortality of the noble scallop Chlamys nobilis cultivated in the South coast of China. It is well known that enzymic system and non-enzymic system both play crucial roles in all living organisms against severe environments. To investigate how change about enzymic system and non-enzymic system in the stenohaline marine bivalve under low salinity stress, an acute challenge lasting 48 hr was conducted using golden and brown noble scallops in the present study. The serine proteinase inhibitor from the noble scallop (CnSPI) was first cloned and expressed in different tissues. After low salinity stress, the gene expression levels were determined in haemocytes and compared between golden and brown scallops. Meanwhile, total carotenoids content (TCC) in adductor, superoxide dismutase (SOD) enzymatic activity and methylenedioxyamphetamine (MDA) content in gill and haemocytes were also determined and compared between the two colours scallops. Results showed that the CnSPI gene expression levels were significantly decreased after low salinity stress, and the golden scallops had higher gene expression levels than brown scallops (p < .05) at most times. Moreover, after low salinity stress, TCC, SOD enzymatic activity and MDA content also fluctuated, and the golden scallops contained higher TCC and SOD, but lower MDA than the brown ones. The present results indicated that enzymic system and non-enzymic system were both changed under low salinity stress in the noble scallop and significantly different responses to the stress existed between golden and brown individuals. The SPI gene and carotenoids (CAR) both play a resistant role to low salinity stress in the noble scallop.

Differential expressions of HSP70 gene between golden and brown noble scallops Chlamys nobilis under heat stress and bacterial challenge

Heat shock proteins (HSPs) are a family of conserved proteins that enhance stress resistance and protect cells from external damage. In the present study, the full-length HSP70 cDNA from the noble scallop Chlamys nobilis (designated CnHSP70) was first cloned and characterized. Then, the expression of CnHSP70 in golden and brown scallops with different carotenoid content was evaluated under heat stress and Vibrio parahaemolyticus challenge. The complete CnHSP70 cDNA is 2621 bp, including a 1971 bp open reading frame (ORF) encoding a polypeptide of 656 amino acids with an estimated molecular weight of 71.55 kDa and an isoelectric point of 5.32. Based on amino acid sequence and phylogenetic analysis, the CnHSP70 gene was identified as a member of the cytoplasmic HSP70 family. The CnHSP70 was ubiquitously expressed in all examined tissues, including intestines, hemocytes, mantle, adductor and gills, with the highest expression in gills. After heat stress and V. parahaemolyticus injection, the expression levels of CnHSP70 in gills and hemocytes of golden and brown scallops were both significantly increased, indicating that the gene was involved in resistance or immune response. Moreover, under both conditions, similar expression profiles of CnHSP70 were observed between gills and hemocytes from the same color scallop, but different expression levels were detected in the same tissue from the different color scallop, which may be related to difference in their carotenoids content.

Sperm cryopreservation of the noble Scallop Chlamys nobilis by a programmable freezing method: Effect of cryoprotectant

A study on Chlamys nobilis sperm cryopreservation by a programmable freezing method was conducted under laboratory condition. Four cryoprotectant agents (dimethyl sulfoxide [DMSO], methanol [MET], propanediol[PG] and ethylene glycol [EG]) and four concentrations (5%, 10%, 20% and 30%) were evaluated for their ability to retain sperm motility, movement characteristics and fertility. Results showed that cryopreserved sperm total motility produced by DMSO and MET at 5%, 10% and 20% were higher than other cryoprotectant treatment groups (CPA groups), as well as rapid sperm percentage. The curvilinear (VCL) and straight line (VSL) velocity produced by DMSO at 5% significantly higher than other CPA groups (p < 0.05), while no significant differences were found for average path (VAP) velocity. The lateral head displacement (ALH) in all CPA groups was similar and without significant difference (p > 0.05), as well as the beat-cross frequency (BCF). A significant higher fertilization rate was produced in DMSO than that in MET at same concentration (p < 0.05), and no significant differences were found for differing concentrations of the same cryoprotectant (p > 0.05). Overall, 5%-20% DMSO was more suitable for Chlamys nobilis sperm programmable cryopreservation when the calcium-free Hanks’ balanced salt solution was used as the extender, and 10°C/min from 0°C to −80°C was used as freezing rate. The findings presented in this study will benefit conservation programs for Chlamys nobilis.

Identification of two ferritin genes and their expression profiles in response to bacterial challenge in noble scallop Chlamys nobilis with different carotenoids content

As a major intracellular iron storage protein, ferritin plays important roles in iron homeostasis and innate immunity. In this study, two novel ferritin subunits from noble scallop Chlamys nobilis (CnFer1 and CnFer2) were identified and analyzed. The open reading frame of CnFer1 and CnFer2 was 522 and 519bp long, encoding 173 and 172 amino acids, respectively. Both ferritins contained a putative iron-binding region signature (IBRS). Analysis of putative conserved domains showed the two CnFer genes contained three key domains of ferritin subunits, a ferroxidase diiron center (E25, Y32, E59, E60, H63, E105, and Q139), an iron ion channel (H116, D129, E132) and a ferrihydrite nucleation center (D58, E59, and E62) that present in M type subunits. A putative iron response element (IRE) was observed at both CnFer genes in the 5’ UTR. Phylogenetic analysis result suggested that the two genes are cytoplasmic ferritins and have the closest evolution relationship with ferritins from Mizuhopecten yessoensis. The two ferritin genes were wildly expressed in examined tissues and the highest level was found in gill. After V. parahaemolyticus challenged, both CnFer genes were significantly up-regulated suggesting that they are important proteins involved in host immune defense. Moreover, under bacterial challenge, the expression levels of both two genes in Golden scallops (rich in carotenoids) were significantly higher than that in Brown scallops (less in carotenoids) which suggesting that carotenoids enhance the immunity in scallops to defense against the bacterial stress.