Razor Clam Research Articles

Using empty shells to study a population of Pacific razor clams in Clam Beach, Humboldt County, California

Using empty shells to study a population of Pacific razor clams in Clam Beach, Humboldt County, California

Integrated physiological, transcriptomics and metabolomics analyses provide insights into thermal stress of razor clam, Sinonovacula constricta

Integrated physiological, transcriptomics and metabolomics analyses provide insights into thermal stress of razor clam, Sinonovacula constricta

Environmental effects on abundance and size of harvested bivalve populations in intertidal shellfish grounds

Clams, razor clams and cockle are intertidal bivalve species collected on foot in the shellfish grounds of the Rías Altas (NW Spain). Spatio-temporal distribution of these bivalves are typically at the expenses of the environmental conditions of the region; however, the responses to the abiotic conditions are poorly understood. Using data from 6 species (Ruditapes decussatus, Venerupis corrugata, Ruditapes philippinarum, Cerastoderam edule, Donax trunculus and Solen marginatus) sampled in 51 intertidal shellfish grounds during 2007 and 2008, we characterized the influence of the environment (temperature, salinity, nutrient salts, suspended organic matter, or sediment granulometry and composition) on the distribution and size of these species through a comparative statistical analysis. Shellfish grounds were grouped according to their sediment and water characteristics revealing a land-ocean gradient and the influence of the geological imprint that separates bivalve grounds from West to East. Statistical models showed that R. decussatus, V. corrugata and R. philippinarum together with C. edule were more abundant in sites combining a strong marine influence with organic-rich finer sediments. However, each of those species also had different environmental niches mostly related to their particular sediment affinities, the proximity to the river mouth, and their physiological tolerances to temperature and salinity. D. trunculus was only found in outer exposed shellfish grounds, while S. marginatus abundance increased in muddy sediments. River distance was a sound descriptor of individual shell length and length variability with contrasting effects on the different species. Furthermore, slopes of length-weight relationships were steeper in autumn than in spring, and this allometry tended to be more positive in sites located closer to the rivers’ mouth, which had a higher organic matter C/N ratio. Overall, harvested intertidal bivalves had identifiable environmental preferences that influence their spatial distribution in abundance, body size, and allometric growth.

Assessing the value of harmful algal bloom forecasts in the Pacific Northwest

Abstract Over the past three decades, fisheries and livelihoods on the coasts of Washington and Oregon have been severely impacted by the presence of harmful algal blooms (HABs) that produce domoic acid, a neurotoxin that accumulates in shellfish and endangers public health. Among others, recreational razor clams and commercial Dungeness crab fisheries along the Pacific Northwest (PNW) have been negatively affected, jeopardizing the economies of coastal communities that depend on tourist revenues and income generated through visits of harvesters in the region. The PNW HAB Bulletin, launched in 2008, publishes forecasts on incoming HAB events, which has enabled managers to increase toxin monitoring in high-risk locations and proceed with selected harvesting at safe beaches and delays or closures of fishing seasons, as required. In light of the value of the HAB Bulletin to local managers and communities and the occasional challenges of securing sufficient resources to ensure its continuation, this study attempts to assess the value of information (VOI) for the predictions provided by the Bulletin. Results of the study show that ongoing financial support of the Bulletin is economically justifiable. The value of HAB forecast is positively related to three primary factors: the frequency of HAB events, the precision of forecast, and the number of social and economic sectors benefiting from the forecast. The expected increase in HAB frequency and intensity due to climate change, coupled with advancements in forecasting accuracy through technological development, is anticipated to enhance the value of the forecast program.

Risk assessment of As, Cd, Cr, and Pb via the consumption of seafood in Haikou

In order to mitigate the risk of excessive heavy metal intake, a study was conducted to assess the levels of arsenic (As), cadmium (Cd), chromium (Cr), and lead (Pb) contamination in 23 edible seafood species obtained from markets in Haikou. The findings were analyzed to evaluate the potential health hazards posed to the local population through consumption. The metals were detected via inductively coupled plasma mass spectrometry (ICP-MS) for quantification. The non-carcinogenic and carcinogenic health risks in humans were assessed via target hazard quotient (THQ), combined target hazard quotient (CTHQ), and target cancer risk (TR). The results indicated that the rank order based on the median metal concentration was As > Cd > Cr > Pb. THQ and CTHQ showed that nine seafood species posed a non-carcinogenic risk regarding from As and Cd consumption separately, or the four targeted metals ingestion together. TR assessment indicated that the InAs in all the species presented a carcinogenic risk to coastal residents. The Cd content in bivalves, algae, and several crustacean (Mantis Shrimp, Orchid Crab, Red spot Swimming Crab) and fish species (Japanese Scad, Pacific Saury), and Cr levels in most bivalve species (Razor Clams, White Clams, Fan Shells, Oysters, Blood Clams) presented a carcinogenic risk. The As, Cd, Pb, and Cr levels of seafood in Haikou were assessed species presented a potential health risk. Necessitating stricter risk should be management and detection capability and monitoring will be improved.

Salinity tolerance assessment of different families of the razor clam Sinonovacula constricta using physiological traits

Salinity tolerance is a complex multigenic trait influenced by genetic factors, environmental factors, and their interactions. However, there are few reports of salinity tolerance assessments using multiple indexes in aquaculture animals. Membership function (MF) analysis is a comprehensive, reliable and valid approach to evaluating resistance by considering multiple indexes. This study primarily aimed to evaluate the salt tolerance of the razor clam Sinonovacula constricta based on physiological traits. In this study, six families of S. constricta (1–1, 1–2, 19–1, 19–2, 17–1, and 14–2) were subjected to high salt stress (30 and 35 ppt). Eight physiological traits (enzyme activity) were employed to assess the high salt tolerance using MF analysis. The razor clams in family 19–2 were all dead at the end of the experiment. The mortality rate (MR) of family 17–1 was significantly lower than that of the other families (P < 0.05). The eight physiological traits showed a remarkable positive or negative correlation among them and did not exhibit specificity with salinity. The MF analysis indicated that family 17–1 displayed the highest resistance and family 19–2 showed weak resistance. The high-resistance families showed lower MR and higher enzyme activity compared with the low-resistance families. The degree of dispersion of enzyme activity at different time points was also a good indicator of the resistance based on the boxplots. Grey relational analysis (GRA) showed that most physiological traits reflected salinity tolerance, with a significant correlation observed with malondialdehyde content. Different families of razor clam showed different sensitivities to high salt levels, which is an important prerequisite for family selection. Additionally, we demonstrated the feasibility of using MF and GRA for evaluating high salt tolerance based on physiological traits. Thus, this study serves as a foundation for stress resistance assessment using physiological traits in aquaculture species.

Unravelling the neuroendocrine system of nocturnal spawning regulated by circadian clock in the razor clam, Sinonovacula constricta

The razor clam (Sinonovacula constricta), as one of important cultivated molluscs, holds high economic importance. Unlike other bivalve species, S. constricta exclusively spawns at night, so the endogenous regulatory mechanisms driving spawning were preliminarily investigated. To identify crucial genes/proteins that may be involved in regulating nocturnal spawning, ovarian transcriptomes and phosphoproteomes were analysed at four diurnal time points (00:00/ZT16, 06:00/ZT22, 12:00/ZT28, 18:00/ZT34) in S. constricta. Transcriptome analysis revealed 503 and 25 differentially expressed genes (DEGs) when comparing ZT16 vs ZT28 and ZT22 vs ZT34, respectively. DEGs associated with energy and substance metabolism, were predominantly overexpressed in ZT16. Notably, genes related to the circadian clock, the neuro-endocrine system, and reproduction, such as clock, timeless homolog (htim), estradiol 17-beta-dehydrogenase (hsd17b11), 5-hydroxytryptamine receptor (htr), and forkhead box protein O (foxo), exhibited significant changes between the light and dark cycles (P < 0.05). Phosphoproteome analysis identified 177 differentially phosphorylated proteins at ZT16 vs ZT28, which were mainly involved in energy and substance metabolism. The association analysis showed that reproduction related proteins including FoxO were heightened phosphorylation at ZT28. Based on our findings, the circadian clock (clock, htim, etc.), neuro-endocrine system (hsd17bs, htr, gpcr, etc.), and reproduction (foxo and rptor) genes and protein phosphorylation all exhibited circadian rhythm fluctuations, suggesting that they may all be involved in nocturnal spawning of razor clams. These findings establish a foundation for understanding the molecular mechanisms underlying spawning and offer valuable insights into the artificial breeding of molluscs.

Integrated application of multi-omics and biochemical analysis revealed the physiological response mechanism of ammonia nitrogen tolerance in the razor clam (Sinonovacula constricta)

Integrated application of multi-omics and biochemical analysis revealed the physiological response mechanism of ammonia nitrogen tolerance in the razor clam (Sinonovacula constricta)

Razor clam (Pinna bicolor) structural mimics as drivers of epibenthic biodiversity; a manipulative experiment

Shellfish ecosystems facilitate important ecological functions and communities, but overexploitation and mismanagement have contributed to their decline worldwide. Within recent decades, coastal management efforts have increasingly sought to understand and reinstate valuable ecological functions provided by habitat-forming bivalves including oysters, mussels and pinnids. However, many bivalve species are critically understudied, limiting restoration and ecological engineering opportunities. Pinnids, specifically, are an underappreciated bivalve group, with razor clams (Pinna bicolor) forming dense aggregations, and potentially supporting important ecological functions. This study, conducted in an urban Australian estuary, was a manipulative experiment that investigated whether artificial razor clam shells could facilitate beneficial ecological functions through the provision of structural habitat. Specifically, we investigated the influence of intertidal benthic structures, including the micro-habitat influences of surface structure associated with mortality status (open or closed shell), and the short-term response of the benthic and epifaunal communities. Within 12 weeks, the structural razor clam mimics rapidly changed the aboveground ecological community, relative to the bare habitat controls. Both open and closed artificial shells provided a settlement surface for epiphytic organisms and supported enhanced epifaunal biodiversity. Contrastingly, the artificial structures did not significantly alter sediment characteristics or infaunal macroinvertebrate composition in the surrounding benthos. These results provide important insights into the rapid ecological response to the installation of intertidal pinnid structures in dynamic estuarine ecosystems. Furthermore, we provide a case study for understanding the ecological functions of an understudied habitat-forming species, which could be used to inform future restoration and management efforts.

Feasibility study of underwater drilling robot based on razor clam

Razor acis lives in the low tidal area of the inner bay and thrives in the area with mild infiltration of fresh water. It uses its rhythmic contraction and foot burp and its unique anatomy to make holes. The extraordinary ability of razor clams to effectively penetrate the sediment has inspired innovation in the design of underwater drilling robots. Underwater drilling robots are currently widely used in the industrial world, such as underwater geological exploration, underwater shipwreck exploration, etc. However, the existing models of these robots mainly have a rigid structural design, which limits the flexibility of their drilling components, while their rough appearance also hinders their drilling efficiency. In response to these limitations, this paper proposes a robot with a soft, flexible body, and other enhanced functions designed to simulate a soft razor clam, replicate its peristaltic motion, minimize surface friction, and thus achieve superior drilling capability. This paper focuses on the development of software, segmented structure design, and studies designed to reduce surface friction and explore the mechanism of biomimetic motion.

Influencing mechanism of farming clams on the CO2 flux from aquaculture ponds: Insights from ecosystem carbon metabolism

Aquaculture ponds have garnered increasing attention for their potential roles in the global carbon cycle within the context of global warming. As a significant co-culture species in mariculture ponds, clams exert a notable impact on CO2 flux across the water-air interface. However, the mechanism underlying this influence is as yet unclear. This study measured the CO2 flux as well as the ecosystem carbon metabolism and environmental physiochemical parameters from four marine polyculture ponds, i.e., the pond containing swimming crabs and kuruma shrimp was referred to as CS, and the other three ponds containing three varying densities of razor clams additionally based on CS were noted as CSB1, CSB2, and CSB3 in order of increasing clam density. All the bi-species and tri-species polyculture ponds acted as atmospheric CO2 sinks during the farming season, with the peak in CSB1 and the lowest in CSB3. Net ecosystem production was a dominant regulator of CO2 uptake, and sediment respiration significantly increased CO2 production and then affected the CO2 flux, contributing 16.7–20.0 % to the ecosystem respiration (ER). Water pH could function as a potentially reliable CO2 flux predictor in the polyculture ponds, while Chl a was an internal driving factor. The polyculture of clams at low density may have exerted a “bottom-up” effect, accelerating nutrient cycling and thus stimulating the planktonic community, gross primary production (GPP), and ER, whereas a high stocking density of clams can have a “top-down” effect that would have the opposite ecological effects through increased predation pressure from clams. Although GPP and ER were simultaneously promoted or inhibited by clams at different stocking densities, the effect on GPP was always greater than that on ER, resulting in the CO2 sink function that the polyculture ponds performed through the water-air interface being strengthened at low clam densities and weakened at high clam densities. Given the good predictive ability of water pH on CO2 flux, monitoring and management of water pH could be an effective way to regulate the CO2 sink function of mariculture ponds.

Design and component simulation study of a hydraulic razor clam seedling dispensing device

Razor clams are a type of economically farmed shellfish widely cultivated in China's coastal areas. Currently, seedling dispersion is still done manually, which requires high labor intensity and incurs high costs. To address this issue, this paper designs a hydraulic razor clam seedling dispensing device and conducts simulation studies using Fluent software to investigate the effects of flow rate ratio q, area ratio m, and the diffusion angle of the diffusion tube on the pressure ratio h and efficiency . With the goal of optimizing seedling dispersion efficiency, the optimal parameters for the jet pump were determined. Under the conditions of a flow rate ratio of 0.03, an area ratio of 2, and a diffusion angle of 8, the simulated seedling dispersion efficiency was found to be 9.60%. A test bench was set up, and bench tests were conducted. The results showed that the actual measured efficiency of the device was 10.40%, with a deviation between the simulated and actual values of 8.33%. The simulation model established in this paper is essentially consistent with actual conditions, providing a reference for the design and improvement of hydraulic seedling dispensing devices.

Proline metabolism and its osmotic regulatory role in enhancing hypersalinity tolerance of the razor clam (Sinonovacula constricta)

Proline serves as an important osmolyte in maintaining osmotic pressure and stabilizing cellular structure in aquatic organisms, and is essential for adaptation to salinity stress. This study focuses on the razor clam (Sinonovacula constricta), and investigated the metabolism and synthesis of proline in response to changing salinity. The proline content in gill tissues of razor clams significantly increased over time and with different levels of salinity exposure. The key genes involved in proline metabolism, including (Aminotransferase (ScOAT), Δ1-pyrroline-5-carboxylic acid synthase (ScP5CS), and proline dehydrogenase (ScProDH) were investigated, as well as enzyme activities associated with these genes in razor clams. The expression and activity of P5CS increased significantly under hypersalinity conditions, whereas that of OAT enzyme activity decreased. This suggested that the glutamate pathway had an important role in the proline synthesis during hypersalinity. ProDH activity was negatively correlated with salinity and regulated by the proline content, indicating a significant role of ProDH in proline accumulation under hypersalinity conditions. ScP5CS was heterologously expressed in yeast Saccharomyces cerevisiae, followed by exogenous proline supplementation studies. Recombinant S. cerevisiae incubated with ScP5CS exhibited elevated levels of proline, with the growth performance of recombinant strain surpassing that of the control group after salinity stress. In addition, razor clams exposed to exogenous proline under high salinity conditions showed expedite osmotic regulation, whereby the hemolymph pressure reached equilibrium more quickly. Together, these results indicated that the proline content increased under high salinity, which could improve the tolerance of razor clams to hypersalinity, offering novel perspectives into molecular mechanism of salinity adaptation in shellfish.

Room-temperature fabrication of fluorinated covalent organic polymer @ Attapulgite composite for in-syringe membrane solid-phase extraction and analysis of domoic acid in aquatic products

A novel fluorinated covalent organic polymer @ attapulgite composite (F-COP@ATP) was prepared at room temperature for in-syringe membrane solid-phase extraction (SM-SPE) of domoic acid (DA) in aquatic products. Natural ore ATP has the advantages of low cost, good mechanical strength and abundant hydroxyl group on its surface, and in-situ modified F-COP layer can provide abundant adsorption sites. F-COP@ATP combining the advantages of F-COP and ATP, becomes an ideal adsorbent for DA extracting. Moreover, a high-throughput sample preparation strategy was carried out by using the F-COP@ATP membrane as syringe filter and assembling syringes with a ten-channel injection pump. In addition, the experimental factors were optimized, such as pH of extract, amount of adsorbent, velocity of extraction and desorption, type and volume of desorption solvent. The DA analytical method was established by SM-SPE-HPLC/tandem mass spectrometry. The method had a wide linear range with low limit of detection (0.344 ng/kg) and low limit of quantification (1.14 ng/kg). F-COP@ATP membrane can be reused more than five times. The method realized the analysis of DA in scallop and razor clam samples, which shows its application prospect in practical analysis. This study provided an efficient, low-energy and mild idea for preparing other reusable natural mineral ATP-based composite materials for separation and enrichment, which reduces the experimental cost and is closer to environmental protection and green chemistry to a certain extent.

Molecular identification of Sinonovacula constricta, Sinonovacula rivularis and their interspecific hybrids using microsatellite markers

The razor clam Sinonovacula constricta, is one of the most commercially important cultured bivalves in China and Southeast Asia, while S. rivularis is its closer relatives discovered more than a decade ago. In order to obtain offspring with faster growth rate and stronger salt tolerance of S. constricta and S. rivularis, interspecific hybrids were produced, and the hybridity of the interspecific hybrids was confirmed by microsatellite markers. Microsatellite markers exhibit a high potential for transfer through cross-amplification in related species, and the transferability of 48 pairs of microsatellite marker primers from S. constricta were assessed in S. rivularis. Here, 24 universal microsatellite markers were successfully amplified in S. rivularis, of which 18 were polymorphic with the allele number from 2 to 5. The genetic diversity of two razor clams evaluated by 18 polymorphic microsatellite markers indicated that two species were both above the middle level, with a relatively higher genetic diversity, while S. constricta showed higher genetic diversity than S. rivularis according to the genetic parameters of Na, Ho, He and PIC. Furthermore, a total of two species-specific microsatellite markers were screened, which could be used for quick genetic identification of S. constricta, S. rivularis and their hybrids. The results suggest the induced interspecific hybrids are true hybrids between S. constricta and S. rivularis, which provide a basis for breeding, subsequent protection, and germplasm resources utilization of the razor clams.

Identification and functional analysis of Toll-like receptor 2 from razor clam Sinonovacula constricta

Toll-like receptor 2 (TLR2) is a member of TLR family that plays important roles in the innate immune system, such as pathogen recognition and inflammation regulation. In this study, the TLR2 homologue was cloned from razor clam Sinonovacula constricta (denoted as ScTLR2) and its immune function was explored. The full-length cDNA of ScTLR2 comprised 2890 nucleotides with a 5′-UTR of 218 bp, an open reading frame of 2169 bp encoding 722 amino acids and a 3′-UTR of 503 bp. The deduced amino acid of ScTLR2 showed similar structure to TLR2 homologue with a conserved signal peptide, four LRR domains, one LRR-TYP domain, one LRR-CT domain, one transmembrane domain and a conserved TIR domain. ScTLR2 mRNA was detected in all examined tissues with the highest expression in the gill. After Vibrio parahaemolyticus challenge, the mRNA expression of ScTLR2 was significantly induced both in gill and haemocytes. The recombinant ScTLR2-LRR protein could bind all tested PAMPs including LPS, PGN and MAN. Bacterial agglutination assay showed that rScTLR2 could agglutinate the six tested bacteria with a calcium dependent manner. More importantly, ScTLR2 silencing by siRNA transfection could significantly depress the mRNA expression of Myd88, NF-κB, Tollip, IRF1, and IRF8. The survival rate of S. constricta was markedly decreased after V. parahaemolyticus challenge under this condition. Our current study demonstrated that ScTLR2 served as a pattern recognition receptor to induce immune response against invasive pathogen.

Effects of medium- and long-term high-salinity environments on free amino acid content and related genes of Sinonovacula constricta

IntroductionThe razor clam, Sinonvacula constricta, one of the important mariculture bivalves in China, has unique flavor and wide salinity adaptability. The unique flavor mainly depends on the content of free amino acids and other umami substances in vivo. However, the flavor divergence of razor clam caused by the variable salinity breeding environment, while the mechanisms remain unclear.MethodsHere, the razor clams were cultured in high salinity (30 ppt) and normal salinity (20 ppt) for eight weeks, and the effects of salinity on free amino acids and related genes expression in S. constricta were investigated by transcriptomics and metabolomics method.ResultsThe results showed the free amino acid content under high salinity environment was significantly higher than normal salinity environment through the duration of the experiment (P &amp;lt; 0.05). The combination of transcriptomic and metabolomic data also indicated that high salinity environment resulted in enhanced metabolism of free amino acids. Furthermore, eight genes such as RALDH2, ACOX1, ALDH-E2 were potentially important for enhancing free amino acids metabolism under high salinity environment.DiscussionThis study preliminarily explained the regulation processes of high salinity environment on the metabolism of free amino acids in razor clams, providing a reference for the flavor regulation mechanism.

Effects of dredging wastewater input history and aquaculture type on greenhouse gas fluxes from mangrove sediments along the shorelines of the Jiulong River Estuary, China

Dredging wastewater (DW) from aquaculture ponds is a major disturbance factor in mangrove management, and its effects on the greenhouse gas (GHG) fluxes from mangrove sediment remain controversial. In this study, we investigated GHG (N2O, CH4, and CO2) fluxes from mangrove sediment at typical aquaculture pond–mangrove sites that were stimulated by DW discharged for different input histories and from different farm types. The GHG fluxes exhibited differing cumulative effects with increasing periods of DW input. The N2O and CH4 fluxes from mangrove sediment that received DW inputs for 17 y increased by ∼10 and ∼1.5 times, respectively, whereas the CO2 flux from mangrove sediment that received DW inputs for 11 y increased by ∼1 time. The effect of DW from shrimp ponds on the N2O flux was significantly larger than those of DW from fish/crab ponds and razor clam ponds. Moreover, the total global warming potentials (GWPs) at the field sites with DW inputs increased by 29–129% of which the CO2 flux was the main contributor to the GWP (85–96%). N2O as a proportion of CO2-equivalent flux increased from 2% to 12%, indicating that N2O was an important contributor to the increase in GWP. Overall, DW increased the GHG fluxes from mangrove sediments, indicating that the contribution of mangroves to climate warming was enhanced under DW input. It also implies that the carbon sequestration potential of mangrove sediments may be threatened to some extent. Therefore, future assessments of the carbon sequestration capacity of mangroves at regional or global scales should consider this phenomenon.

Ammonia-induced oxidative stress triggered apoptosis in the razor clam (Sinonovacula constricta).

As one of the most significant contaminants and stressors in aquaculture systems, ammonia adversely jeopardizes the health of aquatic animals. Ammonia exposure affects the development, metabolism, and survival of shellfish. However, the responses of the innate immune and antioxidant systems and apoptosis in shellfish under ammonia stress have rarely been reported. In this study, razor clams (Sinonovacula constricta) were exposed to different concentrations of non-ion ammonia (0.25mg/L, 2.5mg/L) for 72h and then placed in ammonia-free seawater for 72h for recovery. The immune responses induced by ammonia stress on razor clams were investigated by antioxidant enzyme activities and degree of apoptosis in digestive gland and gill tissues at different time points. The results showed that exposure to a high concentration of ammonia greatly disrupted the antioxidant system of the razor clam by exacerbating the accumulation of reactive oxygen species ( , H2O2) and disordering the activities of antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase), and the level of activity remained at a significantly high level after recovering for 72h (P < 0.05). In addition, there were significant differences (P < 0.05) in the expression of key genes (Caspase 7, Cyt-c, Bcl-2, and Bax) in the mitochondrial apoptotic pathway in the digestive glands and gills of razor clams as a result of ammonia stress and were unable to return to normal levels after 72h of recovery. TUNEL staining indicated that apoptosis was more pronounced in gills, showing a dose and time-dependent pattern. As to the results, ammonia exposure leads to the activation of innate immunity in razor clams, disrupts the antioxidant system, and activates the mitochondrial pathway of apoptosis. This is important for comprehending the mechanism underlying the aquatic toxicity resulting from ammonia in shellfish.

NADK-mediated proline synthesis enhances high-salinity tolerance in the razor clam

Euryhaline organisms can accumulate organic osmolytes to maintain osmotic balance between their internal and external environments. Proline is a pivotal organic small molecule and plays an important role in osmoregulation that enables marine shellfish to tolerate high-salinity conditions. During high-salinity challenge, NAD kinase (NADK) is involved in de novo synthesis of NADP(H) in living organisms, which serves as a reducing agent for the biosynthetic reactions. However, the role of shellfish NADK in proline biosynthesis remains elusive. In this study, we show the modulation of NADK on proline synthesis in the razor clam (Sinonovacula constricta) in response to osmotic stress. Under acute hypersaline conditions, gill tissues exhibited a significant increase in the expression of ScNADK. To elucidate the role of ScNADK in proline biosynthesis, we performed dsRNA interference in the expression of ScNADK in gill tissues to assess proline content and the expression levels of key enzyme genes involved in proline biosynthesis. The results indicate that the knock-down of ScNADK led to a significant decrease in proline content (P<0.01), as well as the expression levels of two proline synthetase genes P5CS and P5CR involved in the glutamate pathway. Razor clams preferred to use ornithine as substrate for proline synthesis when the glutamate pathway is blocked. Exogenous administration of proline greatly improved cell viability and mitigated cell apoptosis in gills. In conclusion, our results demonstrate the important role of ScNADK in augmenting proline production under high-salinity stress, by which the razor clam is able to accommodate salinity variations in the ecological niche.