Golden Scallops Research Articles

Nutrient comparisons among the noble scallops Chlamys nobilis with three different shell colours to provide advices for consumers to choose high-quality food

IntroductionIn aquatic animals, colors not only reflect their sensory qualities but also affect their nutritional components and market price. Noble scallop Chlamys nobilis is an importantly economical bivalve cultured in the south sea of China and renowned for its various shell colors.MethodsIn this study, the nutrient compositions were compared among golden, yellow, and brown shell colour noble scallops originating from the same population for breeding new varieties.ResultsAmong three colour scallops, there is no significant difference in the content of moisture, ash, and total protein content (TPC) but significant differences in total carotenoid content (TCC), total lipid content (TLC), and amino acids (AAs) (P < 0.05), with the TCC of the brown scallop being about 2 times lower. The yellow scallop contained the same nutrients as TCC, TLC, ∑PUFAs (including EPA and DHA), and n-3/n-6 as the golden scallop, and both were significantly higher than the brown scallop (P < 0.05), but they had significantly lower ∑SFAs than the latter (P < 0.05). The correlation between the nutrient indices and the shell color of scallops was 67.5%. There is a significantly positive correlation between TCC and ∑PUFAs (P < 0.05), while a significantly negative correlation exists between TCC and ∑SFAs (P < 0.05). More importantly, the yellow scallop had significantly higher EAAs and FAAs than the golden scallop (P < 0.05).DiscussionThis study showed that the yellow noble scallop not only enriched in carotenoids and PUFAs but also enriched in amino acids. Therefore, the yellow scallop is more benefit to human health, which can provide high-quality food for customers.

Functional Analysis of β-Carotene Oxygenase 2 (BCO2) Gene in Yesso Scallop (Patinopecten yessoensis).

Carotenoids are essential nutrients for humans and animals, and carotenoid coloration represents an important meat quality parameter for many farmed animals. Increasingly, studies have demonstrated that vertebrate carotenoid cleavage oxygenases (CCOs) are essential enzymes in carotenoid metabolism and are therefore potential candidate genes for improving carotenoid deposition. However, our understanding of carotenoid bioavailability and CCOs functions in invertebrates, particularly marine species, is currently quite limited. We previously identified that a CCO homolog, PyBCO-like 1, was the causal gene for carotenoid coloration in the 'Haida golden scallop', a variety of Yesso scallop (Patinopecten yessoensis) characterized by carotenoid enrichment. Here, we found that another CCO-encoding gene named PyBCO2 (β-carotene oxygenase 2) was widely expressed in P. yessoensis organs/tissues, with the highest expression in striated muscle. Inhibiting BCO2 expression in P. yessoensis through RNA interference led to increased carotenoid (pectenolone and pectenoxanthin) deposition in the striated muscle, and the color of the striated muscle changed from white to light orange. Our results indicate that PyBCO2 might be a candidate gene used for improving carotenoid content in normal Yesso scallops, and also in 'Haida golden scallops'.

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.

Identification of a key gene StAR-like-3 responsible for carotenoids accumulation in the noble scallop Chlamys nobilis

Carotenoids play important roles in living organisms. However, animals cannot synthesize carotenoids by themselves, and they must absorb and accumulate carotenoids from their diets in which some key genes are involved. In present study, a gene named StAR-like-3 was characterized in the noble scallop Chlamys nobilis, and its function was identified using golden scallops with higher carotenoids content and brown scallops with less carotenoids content by immunohistochemistry, carotenoid binding assay and RNAi. Results showed that the StAR-like-3 encodes a 54.7 kDa transmembrane protein (named as StAR3) of 481 amino acids containing a MENTAL domain and a START (Steroidogenic acute regulatory protein-related lipid transfer) domain, and its expression level in hemocytes and intestine of golden scallops were significantly higher than those of brown ones. Subsequently, the StAR3 protein was detected in the intestinal epithelial cells of golden scallops, and recombinant StAR3 could bind lutein conjugated to protein G and antibody to form a yellow complex, suggesting it is a carotenoid binding protein involving in carotenoids accumulation in golden scallops. Furthermore, total carotenoids content of hemolymph in golden scallops was significantly decreased when the expression of StAR-like-3 suppressed, suggesting this gene plays an important role in transport of carotenoids. Conclusion, the present results indicated that the StAR-like-3 is a key gene responsible for the carotenoids accumulation in the scallop.

Identification of genes associated with carotenoids accumulation in scallop (Patinopecten yessoensis)

Carotenoids are key nutrients and common pigments for marine species, but the underlying mechanism of carotenoids bioavailability is unclear. In this study, genome-wide association study (GWAS) was performed for pectenolone and pectenoxanthin content in the adductor muscle of “Haida golden scallop”, a variety for Yesso scallop (Patinopecten yessoensis), which was characterized by orange adductor muscle enriched in carotenoids. The most significant SNP was the same for both pectenolone and pectenoxanthin, which was located upstream of two tandem Poly(ADP-ribose) polymerases (PARPs), PARP9/14/15-1 and PARP9/14/15-2. The expression levels of these two PARPs were significantly correlated with the concentrations of pectenoxanthin and pectenolone, respectively. Three other SNPs significantly associated with the concentrations of ketocarotenoid pectenolone were also detected, among which, two were located around another two PARPs (PARP9/14/15-3 and PARP9/14/15-4), and a significant correlation was found between PARP9/14/15-3 expression and pectenolone concentrations; one SNP was near the cluster of Cytochrome P450 2J6 (CYP2J6), a P450 subfamily which has been reported to catalyze ketocarotenoid production. Our data imply the involvement of PARP9/14/15s in carotenoids accumulation and CYP2J6s in pectenolone conversion in scallop.

Genomic differentiation and selection signatures of two elite varieties of Yesso scallop Mizuhopecten yessoensis

Yesso scallop, Mizuhopecten yessoensis, is one of the most important bivalve species in aquaculture industry. Two selective improved varieties (Haida golden scallop and Zhangzidaohong) have been developed by artificial selection in recent years and exhibit good performance on growth and production traits. However, there's still a lack of comprehensive studies to analyze the population differentiation, genomic linkage disequilibrium patterns, as well as the selection signatures of the two elite varieties of Yesso scallop. In the present study, we performed whole genome resequencing of three groups of Yesso scallop to characterize the genetic changes resulted from selective breeding. A total of 9,534,749 high quality single nucleotide polymorphisms (SNPs) were discovered. The two selective varieties exhibited lower genetic diversity and retained relatively large linkage disequilibrium (LD) blocks compared to the reference population. Despite obvious stratification of the population structure of Yesso scallop, medium degrees of genetic differentiation (Fst < 0.15) was detected among the new varieties and the reference population. We highlighted several genes including LPCAT1 and TRAF reveal signatures of artificial selection and these genes would be potentially important for specific characteristics and improved performance in growth and resistance to diseases. The data and findings generated in our project would provide useful additions to currently available genomic resources for scallops and facilitate further genetic improvement and molecular studies in M.yessoensis.

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.

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.

Tissue distribution and seasonal accumulation of carotenoids in Yesso scallop (Mizuhopecten yessoensis) with orange adductor muscle

Carotenoids are colored compounds with important physiological functions. The Haida golden scallop, which has an orange adductor muscle, is a carotenoid-enriched variety of scallop Mizuhopecten yessoensis, an important aquaculture shellfish. In this study, we investigated the tissue distribution of the carotenoids, pectenolone and pectenoxanthin, in both Haida golden scallop and normal Yesso scallop. Both carotenoids were detected in all the sampled tissues of the two scallops, except in the adductor muscle of normal scallop. There were significantly more carotenoids in Haida golden scallop than in normal scallop, in the tissues of the mantle, female gonad, kidney, and adductor muscle. Increased carotenoid concentrations were detected in Haida golden scallop adductor muscle during the spring spawning season, indicating the effects of reproduction on muscle carotenoids accumulation. This study was the first systematic investigation of carotenoid distribution in Yesso scallop tissues and will benefit future research on carotenoid accumulation and function in scallops.

Carotenoids content and lipid nutritional quality variation in tissues of male and female polymorphic (golden and brown) noble scallops Chlamys nobilis

The noble scallop Chlamys nobilis is one of the most important cultured shellfish in Southern China, known for its rich total carotenoids (TCC) and polyunsaturated fatty acids (PUFA). However, carotenoid and lipid nutritional quality of C. nobilis are greatly affected by many factors, including season, sex, and color of C. nobilis. Therefore, this study aims to assess the TCC and lipid nutritional quality of tissues of male and female, golden and brown scallops. The results of the this study revealed that golden scallops generally have much higher TCC, total lipid content (TLC) and PUFA than brown scallops, while female scallops generally have higher TCC, but lower TLC and PUFA than male scallops. In conclusion, golden scallops are more nutritious than brown scallops. Female golden scallops may be more attractive to consumers interested in high natural antioxidant (TCC), while male golden scallops may be more popular for consumers interested in high quality lipids (TLC and PUFA). These data will help consumers determine the best dietary choices based on their nutritional interests.

Genome-wide analysis of TRAF gene family and its response to bacterial infection in noble scallop Chlamys nobilis with different carotenoids content

Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are multifunctional adaptor proteins in the immune system, which play significant roles in the regulation of Toll-like receptor and RIG-I-like receptor signaling pathway in animals. Although many TRAF genes have been identified in mollusks, the systematic identification of the TRAF gene family in noble scallop Chlamys nobilis has not been reported, and very little is known about its roles in scallop innate immunity. In this study, four TRAF genes (CnTRAF 2, CnTRAF3, CnTRAF4 and CnTRAF6) were identified and characterized from C. nobilis. Sequence and phylogenetic analysis revealed that CnTRAFs contain typical conserved domains closely related to TRAFs of other mollusks. The motifs analysis of C. nobilis CnTRAFs also showed that the conserved motifs were identical to other mollusks and vertebrates. The expression pattern of CnTRAF genes in tissues of brown and golden scallops (the carotenoid content of golden scallops is significantly higher than that of brown scallops) were not statistically significant, but in hemolymph of scallops challenged with bacteria, the expression of CnTRAF genes was significantly higher than that of control, suggesting that the CnTRAF genes play vital roles in the immunity of mollusks. Furthermore, at several time points after bacteria challenge, the expression level of CnTRAF genes in golden scallops were significantly higher than that of brown scallops, indicating that carotenoids may enhance CnTRAF genes expression and immunity. The systematic analysis of the roles of TRAFs in C. nobilis provides valuable information for the further researches of CnTRAF genes.

Carotenoids regulation in polymorphic noble scallops Chlamys nobilis under different light cycle

Light cycle is an important factor affecting the total carotenoid content (TCC) in tissues of noble scallops Chlamys nobilis, but its regulatory mechanism is still unclear. In this study, adult polymorphic C. nobilis (Nan'ao Golden Scallop and common brown scallop) were exposed to three different light cycles (24L/0D, 12L/12D and 0L/24D) for 10 days. The expression of carotenoid related genes (Scavenger Receptor class B (SRB) genes, β-carotene oxygenase (BCO) genes, and Retinoic acid receptors (RAR and RXR) genes) were determined by qRT-PCR. The results revealed that 24L/0D and 0L/24D treatments significantly increased the accumulation of TCC in adductor muscle of Nan'ao Golden Scallop and common brown scallop, respectively. The deposition of carotenoids in adductor muscle was induced by the up-regulation of SRB genes, of which was then up-regulation of BCO gene expression, followed by the up-regulation of RAR and/or RXR expression, and then further induced the expression of SRB and BCO genes. In hemolymph, the absorption mechanism of carotenoids may not involve SRB genes, or other carotenoid related genes may mask the role of SRB genes. The findings of this study provide important clues for further understanding the mechanism of TCC accumulation in polymorphic C. nobilis under different light cycle.

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.

Ecological stability of triticale samples in the conditions of the Khabarovsk territory

The new grain crop triticale is of great interest for cultivation in the soil and climatic conditions of the middle Amur Region; therefore, this study assessed the environmental stability of yield formation for a collection of triticale samples. The varieties with the maximum yields identified in the study were the following: AC Certa (Canada), Lana (Belarus), Dagvo (Russia), Golden Scallop (Russia), Ulyana (Belarus), Uzor (Belarus), Lotos (Belarus), Mykola (Ukraine), Victoria (Ukraine), Sandio (Switzerland), Wanad (Poland) and Yarik (Russia). The AC Certa (Canada) variety was characterised by high demands on growing conditions (St2 = 0.69, A = 30.03) and unstable yield (1.8-7.0 t/ha). The Victoria (Ukraine) variety was characterised by high ecological stability of yield (St2 = 0.99, A = 27.45) in various years (2.5-3.1 t/ha). Results indicated that the yield formation of the collection samples were strongly dependent on weather conditions (R=0.554). Lastly, a model of spring triticale yield formation dependent on weather factors was constructed using regression analysis. The most significant climatic factor was photosynthetically active radiation during the active vegetation period

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.

Enzymes and non-enzymatic antioxidants responses to sequential cold stress in polymorphic noble scallop Chlamys nobilis with different total carotenoids content

Noble scallop, an economically important edible marine bivalve displays polymorphism in shells (golden and brown) and flesh colors (orange and white). Mass mortality of noble scallops usually occurs during the winter months. Interestingly, carotenoid-rich golden scallops demonstrated much higher survival rates than brown scallops in winter. In order to understand the response of polymorphic noble scallops to sequential cold stress, the present study aimed to investigate the enzyme and non-enzymatic antioxidant responses of golden and brown scallops under sequential cold stress. Parameters evaluated included total carotenoid content (TCC), fatty acid composition, total antioxidant capacity (TAC), methylenedioxyamphetamine (MDA) content, catalase (CAT) activity, and superoxide dismutase (SOD) enzyme activity. The results of the present study revealed that golden scallops have higher cold tolerance than brown scallops. Golden and brown scallops are well adapted to low water temperature of above 12 °C, but in areas where winter water temperatures are below 12 °C, golden scallops are more suitable for aquaculture than brown scallops. The findings of this study are crucial to understanding the physiological responses of polymorphic scallops to cold stress and identify suitable candidates for winter aquaculture.

Seasonal variation of total carotenoids content in the tissues of male and female golden noble scallops Chlamys nobilis

The noble scallop Chlamys nobilis is an economically important edible marine bivalve that has been cultivated in the Southern Sea of China since the 1980s. Noble scallops, particularly the golden scallops, are rich in carotenoids, are of interest for their potential beneficial uses in human healthcare, food processing and pharmaceuticals. However, very little is known about the seasonal variation of total carotenoids content (TCC) in the golden scallops. Therefore, present study was conducted to determine the seasonal variation of TCC in the tissues of male and female of golden scallops. The results of present study revealed that the TCC in adductor, mantle and gonads of golden scallops were ranged from 16.79 to 138.86 μg/ g, 92.86 to 312.98 μg/ g, and 71.5 to 750.0 μg/ g, respectively. Generally, the gonads of golden scallops contain the highest TCC, followed by the mantle and adductor. In comparison of male and female scallops, TCC in the same tissue (except for gonad) was not statistically significant. However, female gonads contain much higher TCC than male gonads. The temporal variation of the TCC in golden scallops showed the highest in March to April and the lowest in October. The findings of current study can be very useful for scallop farmers and industry to determine the best harvest time to obtain the highest quality of golden scallops with high TCC.

Effects of thermal stress on mortality and HSP90 expression levels in the noble scallops Chlamys nobilis with different total carotenoid content.

The noble scallop Chlamys nobilis is an economically important marine bivalve cultivated in the southern sea of China since the 1980s. Unfortunately, mass mortality of this scallop species often occurs in summer. The present study was conducted to investigate whether the expression of heat shock protein 90 (HSP90) and level of carotenoids could enhance high-temperature stress resistance in scallop. First, the HSP90 homolog of C. nobilis (designated CnHSP90) was identified and cloned. The complete cDNA sequence of CnHSP90 was 2631bp, including a 2181-bp open reading frame (ORF) encoding a 726 amino acid polypeptide with five HSP90 family signatures, and sharing high homology with members of the HSP90 family. CnHSP90 was ubiquitously expressed in all examined tissues including the intestine, kidney, adductor, mantle, gill, and gonad, with the highest in the gonad. Golden and brown scallops, which contain significantly different total carotenoid content (TCC), were subjected to acute thermal challenge, and the LTE50 (semi-lethal temperature at 36h heat shock) and LTI50 (semi-lethal time after heat shock) as well as the correlation between CnHSP90 gene expression and TCC were determined. The LTE50 of golden scallop (32.14°C) was higher than that of brown scallops (31.19°C), with longer LTI50 at all tested temperatures, indicating that golden scallops were more resistant to thermal stress than brown scallops. Similarly, the mRNA expression levels of CnHSP90 in gill of golden scallops were significantly higher (P < 0.05) than that of brown scallops at 6, 12, 24, and 36h, with a strong positive correlation between CnHSP90 expression level and TCC. This suggests that both carotenoids and HSP90 levels could improve thermal resistance in the noble scallops.

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.