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Aquaculture can provide foraging habitat for birds, but it can also result in intentional and accidental mortality. We examined an overlooked conflict between razor clam (Sinonovacula spp.) aquaculture and declining shorebirds in southeastern China's Fujian and Zhejiang provinces. We surveyed 6 out of 11 internationally important stopover sites for these shorebirds and monitored shorebird mortality in 2 sites (Xinghua Bay, Yueqing Bay) with razor clam aquaculture. We visited an additional 32 sites in these 2 provinces to determine if there was netting in other razor clam farms. Approximately 8–9 km2 of intertidal foraging habitat was covered by horizontal nets to prevent birds from feeding on young razor clams at Xinghua Bay and Yueqing Bay. We conservatively estimated that 13,676 (2.5th–97.5th percentile 8,330–21,285) individual shorebirds were entangled in the nets at the 2 monitored sites in April and May 2021, including 2 endangered and 7 near‐threatened species. Mortality of 5 species for which we had sufficient data accounted for 0.76% (black‐tailed godwit [Limosa limosa]) to 4.27% (terek sandpiper [Xenus cinereus]) of their total flyway populations. This level of mortality could strongly affect their populations. We found netting at 17 additional razor clam farms, indicating a widespread threat to shorebirds. Although razor clams are typically harvested in late March to early April, nets are left on the mudflats throughout the spring and summer, including when the bulk of shorebird migration takes place. Immediately removing these nets after the clam harvest could prevent most of the spring mortality of shorebirds, although this is unlikely to happen without government regulations or economic incentives. To better assess and mitigate the impacts of this conflict, future research should quantify shorebird mortality at other razor clam farms, including during winter, explore less harmful deterrence methods, and assess the socioeconomic factors driving the conflict. [ABSTRACT FROM AUTHOR]

The levels of essential (Cu, Cr, Co, Mn, Se, Zn) and non-essential (As, Be, Bi, Cd, Cs, Ga, Ni, Pb, Sr, Tl, U, V) trace elements were studied in razor clams (Solen marginatus) collected from the Tyrrhenian coast of Southern Italy at five selected sites along the Domitio littoral in the Campania region. The main objectives of this study were to assess the contamination status of these bivalve mollusks and to evaluate the risks to the environment and consumers due to metal contamination. The concentrations of 18 trace elements were determined after microwave-assisted mineralization and by inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of the toxic elements Pb and Cd were below the maximum levels established by Commission Regulation (EC) 1881/2006, while higher average concentrations of arsenic were found at each of the five sites studied. Regarding the other trace elements, contamination levels followed the order: Zn > Sr > Mn > Cu > Se > Cr > V > Ni > Co > Ga > Cs > Be > U > Bi > Tl. No significant differences among the sites were found with regard to any of the trace elements analyzed, and element levels in razor clams did not reflect sediment contamination. The results demonstrated the substantial food safety of the razor clams in this area with respect to heavy metals but revealed a potential health risk due to arsenic contamination in all the areas sampled. [ABSTRACT FROM AUTHOR]

Razor clams (Sinonovacula constricta) are one of the major polyculture species in mariculture ponds, along with swimming crabs (Portunus trituberculatus), in the coastal zones of China, and their effect on CO2 fluxes are poorly studied. CO2 fluxes from mariculture ponds with swimming crabs, kuruma shrimp (Marsupenaeus japonicus) (CS) and mariculture ponds with swimming crabs, kuruma shrimp and razor clams (with different clam densities from low to high, CSB1, CSB2, CSB3, respectively) were measured during the farming season. The CO2 fluxes of CS, CSB1, CSB2, and CSB3 were −25.37, −30.23, −28.81 and −12.18 mg m−2 h−1, respectively. All the ponds acted as CO2 sinks across the water-air interface. Our results showed that water pH was a good indicator of the CO2 flux, and a pH value of 8.24 was the critical value dividing the dataset into influxes or effluxes in the mariculture ponds. Net primary production was also significantly correlated with the CO2 flux and is considered a key driver regulating the CO2 flux. Our findings indicate that the low clam stocking density used in this study could enhance the CO2 sink across the water-air interface by promoting phytoplankton biomass and net primary production, whereas the CO2 sink may be weakened with an increase in clam density due to a decline in phytoplankton biomass and net primary production.

The levels of essential (Cu, Cr, Co, Mn, Se, Zn) and non-essential (As, Be, Bi, Cd, Cs, Ga, Ni, Pb, Sr, Tl, U, V) trace elements were studied in razor clams (Solen marginatus) collected from the Tyrrhenian coast of Southern Italy at five selected sites along the Domitio littoral in the Campania region. The main objectives of this study were to assess the contamination status of these bivalve mollusks and to evaluate the risks to the environment and consumers due to metal contamination. The concentrations of 18 trace elements were determined after microwave-assisted mineralization and by inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of the toxic elements Pb and Cd were below the maximum levels established by Commission Regulation (EC) 1881/2006, while higher average concentrations of arsenic were found at each of the five sites studied. Regarding the other trace elements, contamination levels followed the order: Zn > Sr > Mn > Cu > Se > Cr > V > Ni > Co > Ga > Cs > Be > U > Bi > Tl. No significant differences among the sites were found with regard to any of the trace elements analyzed, and element levels in razor clams did not reflect sediment contamination. The results demonstrated the substantial food safety of the razor clams in this area with respect to heavy metals but revealed a potential health risk due to arsenic contamination in all the areas sampled.

Metabolic activities such as breathing and digestion, resulting from natural functions of the body through oxidation, lead to the formation of free radicals that cause cancer, premature cardiac aging and some chronic diseases. Antioxidants are substances that remove free radicals and prevent cell damage. Seafood significantly contributes to the elimination of free radicals, especially owing to its high quality nutrient content. In this context, the objective of the study was to determine the radical antioxidant capacity and the total amount of carotenes in razor clams. The IC50 (mg g−1) value of the DPPH radical sweeping effect varied over the months (p < 0.05), showing the highest value in June, gradually decreasing from September and reaching the lowest level in February. The total amount of carotenoids also varied, with the highest value in September (p < 0.05). The total amount of chlorophyll ranged from 6.15 μg g−1 in August to 66.71 μg g−1 in December. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are anthropogenic contaminants found in coastal and marine environments worldwide. Pacific razor clams (Siliqua patula), important for local indigenous culture, economy, gastronomy and food security along the United States West Coast, are subjected to myriad environmental stressors including predation, storm events, disease, toxins, and MPs. This study aimed to determine MP burdens in Olympic Coast, Washington Pacific razor clams and estimate annual MP exposure of recreational razor clam harvester-consumers from eating this species. We quantified suspected MP burdens in Pacific razor clams collected from eight tribal, recreational, and commercial harvest areas on the Olympic Coast in April 2018. We administered questionnaires to 107 recreational razor clam harvesters during the same timeframe to determine consumption patterns, preparation styles, knowledge and concerns about MPs, and demographics. Razor clams containing suspected MPs, primarily microfibers, were found at all eight sites. Average suspected MP burden differed by sample type (whole = 6.75 ± 0.60, gut-tissue = 7.88 ± 0.71, non-gut tissue = 4.96 ± 0.56, and cleaned samples = 3.44 ± 0.25). FTIR analyses of a random subset of microfiber-type MPs in whole and cleaned clams indicated material types of polyethylene terephthalate, cellulose acetate, cellophane, polyester, nylon, and cellulose. The average number of razor clams consumed per meal by Olympic Coast recreational razor clam harvesters was 4.27 ± 0.27, which varied by gender and ethnicity, but not income or age. Harvesters ate 0–209 meals/year of razor clams (16.2% harvested but did not eat razor clams), and most respondents (88.3%) fully cleaned razor clams before consuming them. Annual suspected MP exposure for razor clam harvester-consumers was 60–3,070 for cleaned and 120–6,020 for whole clams. Our findings suggest Olympic Coast recreational razor clam harvester-consumers are exposed to low levels of MPs from eating razor clams. MP exposure can be reduced by roughly 50% if clams are cleaned before consumption. Our work serves as an important reference in the growing portfolio of Pacific Northwest microplastic research, to inform future MP attenuation recommendations and development of human health standards for this type of pollution.

Refrigerated treatment offers an effective avenue to delay spoilage process of aquatic products during storage, while none or less study has been reported for bivalve species. This work aims to investigate the variations in different storage freshness of frozen razor clam samples, by which an effective evaluation system based on frozen kinetics models was established. In this study, fresh razor clam samples were preserved at the temperature of 268, 258, and 248 K for 40 days, respectively. The spoilage process was determined by a series of freshness assays, including sensory score (SS), electric conduction (EC), total volatile basic nitrogen (TVB-N), K-value, and total colonies counts (TCC). On this basis, the variations in these indexes were fitted by zero-, first- and second- order kinetic models. Results showed that zero -order kinetic model was more suitable to fit each freshness trend. Accordingly, the shelf life of razor clam was predicted as 47∼54, 79∼84, and 121∼154 days when the samples were preserved at 268, 258, and 248 K, respectively. This study revealed the general trends of the frozen decay process of bivalve species, which is instructive to establish applicative models for the real distribution chain. [ABSTRACT FROM AUTHOR]

Razor clam (Sinonovaculaconstricta) is one of the most commercial clam species in China, which is in the Siliqua genus with narrow and slender shells. It has been reported that razor clams are rich in vitamins, amino acids and carbohydrates, and have high nutritional value. However, razor clam is easy to rot during storage, which seriously affects its sensory quality and consumer preferences. Particularly, its abundance of nutrients can lead to high reproduction of microorganisms, thus shortening its shelf life. Therefore, it is highly necessary to propose a novel and efficient sterilization method inhibiting microbial contamination for razor clam preservation. Currently, the anti-microbial photodynamic technology is considered as a novel non-thermal sterilization technology that not only can reduce the microbial growth in foods, but also can preserve their nutritional value, color, quality, and water content. Therefore, the purpose of this study was to investigate the influence of anti-microbial photodynamic technology on the preservation of razor clam. The treated conditions of the anti-microbial photodynamic sterilization for razor clam preservation were optimized by total number of bacterial colony with Box-Behnken experimental design. Meanwhile, sensory evaluation and physicochemical indexes were also evaluated on razor clam after storage at 4℃ for 8 days. The results demonstrated that curcumin-mediated could effectively inhibit the residual bacterial contamination in the razor clam and delay the growth of bacteria. The curcumin concentration, soaking time and LED exposure time were the key factors affecting the antibacterial efficiency of this photodynamic sterilization. The sterilization rate could reach 99.99%, when photodynamic sterilization using 26.6 μmol/L curcumin concentration with 24.8 min soaking time and 20.5 min LED exposure time. In addition, the appearance, color and other sensory characteristics of razor clam were maintained in good condition after anti-microbial photodynamic technology treatment storaged at 4 ℃ for 6 days. Compared with the control group, the physicochemical indexes water content, pH value, thiobarbituric acid and total volatile basic nitrogen values of razor clam were also in desirable range after the optimized anti-microbial photodynamic treatment. The water content of the anti-microbial photodynamic -treated samples was 73.79%, which is significantly higher than that of the control group 59.94%, indicating that treatment of razor clam with curcumin-mediated anti-microbial photodynamic technology might also maintain the water content. In addition, within 6 days of storage, the increase in pH value and decreases in thiobarbituric acid and total volatile basic nitrogen values of razor clam were observed. Moreover, anti-microbial photodynamic technology treatment could significantly delay these changes compared to the control group. In conclusion, this study suggested that the anti-microbial photodynamic technology had good bactericidal activity and could be used for the preservation of razor clam. [ABSTRACT FROM AUTHOR]

The Atlantic razor clam exhibits exceptional penetration performance in wet sands by periodically expanding and contracting its shell and foot during burrowing. Essentially, this periodic penetration movement can be simplified as a cyclic alternation of cylinder expansion and cone penetration, which are analogous to the geotechnical pressuremeter test and the cone penetration test. The dynamic penetration movement of the razor clam was simplified as four major connective steps—cylinder expansion, cone penetration, cylinder contraction, and cylinder retraction—and the kinematics was parameterized based on the biological data. Using a simplified and idealized synthetic dry sand sample, we attempted to model the clam-inspired penetration process using two common geomechanics tools, an analytical model based on cavity expansion theory and a numerical discrete element method (DEM), and to showcase the advantages and limitations of these two approaches in the dynamic penetration modeling. In the analytical model, the four consecutive steps were assumed to be independent. The penetration resistance and energy consumption for each step were therefore roughly estimated using cavity expansion theory; in parallel, the independent cylinder expansion and cone penetration process as well as the clam-inspired coupled dynamic penetration process were also modeled using the DEM method. When the results were compared, it was found that the adopted cavity expansion theory solutions can predict the independent cylinder expansion and cone penetration behaviors, given that the parameters were carefully chosen and calibrated. However, it cannot capture the interference effect in a coupled dynamic penetration process. Specifically, the analytical model overestimates the cone penetration resistance of the coupled dynamic penetration process; the cylindrical shaft expansion causes stress release around the cone, leading to a reduction in the tip resistance as the cone continues to penetrate. The analytical model also underestimates the expansion pressure in the dynamic penetration process, which is attributed to the change in stress and fabric state caused by the cyclic expansion/contraction movement. Moreover, the clam-inspired dynamic penetration was found to reduce the energetic cost on the penetration of cone and shaft for about 36% and still maintain a slightly lower energy consumption with additional cost on the cyclic shaft expansion, compared with the pure cone penetration strategy. With a better future understanding of the highly effective and efficient self-burrowing behavior of natural burrowers, it is envisioned to develop self-burrowing robots for a spectrum of geotechnical applications. [ABSTRACT FROM AUTHOR]

Copper (Cu) is a common pollutant in estuaries and has received considerable attention worldwide. To gain an insight into the physiological mechanisms of waterborne Cu absorption, tissue distribution, storage, metabolism, and excretion in an estuarine razor clam Sinonovacula constricta , we developed a physiologically-based pharmacokinetic model based on prolonged Cu exposure with two exposure treatments. The tissues of S. constricta were divided into four parts: blood, digestive gland, gill, and other tissues. Our results showed that the waterborne Cu entered and exchanged with the gills and digestive gland, whereas digestive gland and other tissues were the main storage sites for Cu. Gills of S. constricta were able to maintain their Cu concentrations under both exposure treatments. Additionally, the gills exhibited a remarkable ability to remove Cu from water, with a transfer rate constant of 1.73 d−1 from the gills to water, while restricting its transfer from the blood with a transfer rate constant of 0.0131 d−1 from blood to gills. These results highlighted the crucial role of gills in regulating Cu levels in S. constricta as well as the detoxification and maintenance of metal homeostasis. Cu uptake rate constant in gill from waterborne was similar to that of digestive gland (0.294 vs. 0.364 L g−1 d−1), thus water entering the digestive tract was considered as another route of waterborne Cu absorption in bivalves. A significant amount of Cu in the blood was transferred to the digestive glands. These two factors explained the relatively higher Cu accumulation in the digestive glands than in other tissues in clams. The findings of this study enhanced our understanding of the homeostatic regulation and transportation mechanisms in marine bivalves. [Display omitted] • A PBPK model was developed to simulate Cu transfer in the clam S. constricta. • The gills played a pivotal role in maintaining and regulating Cu levels. • Gills regulated homeostasis by removing Cu to water and restricting Cu transfer from blood. • Water intake into digestive gland was a significant route for waterborne Cu uptake. • Elevated Cu concentration in digestive gland resulted from both water exposure and blood transfer. [ABSTRACT FROM AUTHOR]

Total lipids were extracted from razor clams Sinonovacula constricta and Solen gouldi, and the molecular species of glycerophospholipid (Gpl) including choline glycerophospholipid (ChoGpl), ethanolamine glycerophospholipid (EtnGpl), serine glycerophospholipid (SerGpl), inositol glycerophospholipid (InsGpl), lysoChoGpl, lysoEtnGpl, and lysoSerGpl were characterized using a direct‐infusion tandem mass spectrometric method for the first time. Meanwhile, the lipid class composition and phospholipid (PL) class composition as well as the fatty acid (FA) composition of total lipids, triacylglycerol (TAG), and PL were also investigated. About 238 and 235 molecular species were characterized, respectively, in Sinonovacula constricta and Solen gouldi. The majority of the dominant Gpl molecular species contained n‐3 long‐chain polyunsaturated fatty acids (n‐3 LC‐PUFA), especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Also, razor clam lipids contained a high‐proportioned PL (52.19–65.41% of total lipids) and PUFA (47.94–54.81 mol%). Furthermore, PL contained a higher proportion of PUFA (63.05–67.13 mol%), especially DHA (20.04–22.47 mol%) and EPA (16.27–21.46 mol%) than TAG (the corresponding values being 33.73–34.45, 11.95–12.27, and 8.13–0.8.99 mol%, respectively). Meanwhile, phosphatidylcholine (44.38–46.21 mol%) and phosphatidylethanolamine (38.84–39.95 mol%) were dominant among PL. In consideration of the high proportion of PUFA‐enriched Gpl, razor clam plays a great role in promoting human health. [ABSTRACT FROM AUTHOR]

Abstract Despite their ecological and economical relevance, a lack of data is still occurring about the distribution, abundance, bioaccumulation and risks for consumption of some edible bivalves. The present study has been carried out in the Venice Lagoon taking into account three bivalve species to investigate i) the possible relationship among the biological features-distribution, abundance and bioaccumulation patterns- of razor clams ( Solen marginatus Pulteney, 1799), Manila clams ( Ruditapes philippinarum Adams and Reeve, 1850) and lagoon cockles ( Cerastoderma glaucum Poiret, 1789) and the hydrological features, namely sediment physico-chemical characteristics and contamination; ii) their specific role as bioindicators of inorganic contamination; iii) the possible risks for human health associated with the consumption of these edible bivalves. Results showed that species distribution and abundance, especially for razor clams, was mainly influenced by environmental conditions and sediment granulometric composition, above metal(loid) contamination. The contamination patterns were different among species, as Manila clam generally showed higher bioaccumulation values for most of the metal(loid)s, whilst lagoon cockles preferentially accumulated Ni. Eventually, a serious concern exists for the human consumption, for all species and investigated sites regarding As. This study will raise attention on the effects of bioaccumulation of inorganic pollutants by edible bivalves and risks for consumers' safety, especially concerning razor clams and cockles, for which a critical lack of data on metal(loid) bioaccumulation occurs from the Northern Adriatic Sea. Graphical abstract Unlabelled Image Highlights • A lack of biological data is still occurring for some edible bivalves. • Razor clam, Manila clam and lagoon cockles have been studied in the Venice Lagoon. • Species occurrence was influenced mainly by sediment granulometry. • Manila clam bioaccumulated most metal(loid)s, lagoon cockles accumulated Ni. • A serious concern exists for the human consumption regarding As. [ABSTRACT FROM AUTHOR]

Galectins are soluble lectins that perform a pattern recognition function in invertebrate immunity and specifically recognise β-galactoside residues via conserved carbohydrate recognition domains. However, their function in bivalve molluscs has received little attention. Herein, a galectin (ScGal2) in razor clam ( Sinonovacula constricta ) consisting of a 507 bp open reading frame encoding a protein of 168 amino acids was identified and characterised. The protein includes a carbohydrate recognition domain (CRD), and several residues involved in dimerisation were found. ScGal2 mRNAs were mainly detected in hemolymph and liver, and expression was upregulated significantly following challenge with Vibrio anguillarum . Recombinant rScGal2 protein displayed strong agglutination activity toward Gram-negative bacteria, and flow cytometry revealed that ScGal2 strongly promoted phagocytosis in hemocytes. These results suggest that ScGal2 plays an indispensable role in innate immunity in razor clam, and likely participates in immune recognition and clearance processes. [ABSTRACT FROM AUTHOR]

Razor clam is a major cultivated shellfish of great economic importance and high nutritional value. Due to high corruptible potential, razor clam is generally preserved by controlled freezing-point storage (CFPS). Here, we applied isobaric tags for relative and absolute quantification (iTRAQ) labeling to investigate the biochemical mechanism of cold stress adaption in razor clam during CFPS. In total, 369 proteins were quantified, and 27 of them were identified as differentially expressed proteins during CFPS, mostly involved in energy metabolism process, DNA duplication and protein synthesis, and stress response, specifically, MAPK is the predominant pathway. Further qPCR results revealed H2A and S6K 2 alpha to be the critical post-transcriptionally regulated genes. Our results provided proteomics information with respect to the biochemical mechanism of cold stress adaption in razor clam, shed light on the further elongation of razor clams storage period, and help clarify the novel mechanisms of cold tolerance. [ABSTRACT FROM AUTHOR]

The population biology of the stout razor clam Tagelus plebeius is poorly understood, despite the species' current wide distribution, and the potential use of its Holocene shell deposits to infer past environmental and ecological conditions. This study investigates distribution and growth pattern of T. plebeius in the south-western Atlantic Mar Chiquita Coastal lagoon (37°32′S 57°19′W), Argentina. The population includes the oldest individuals (up to 27 years) reported so far with shell length up to 77.9 mm. A von Bertalanffy model with L∞ = 67.60 mm (95% CI = 64.55; 70.64), k = 0.181 year−1 (CI = 0.142; 0.218), and t0 = −0.77 (CI = −1.46; −0.08) best described their individual growth for the whole population. The higher density, growth rate k, t0 and maximum age and lower L∞ were in the low intertidal rather than in the medium intertidal, but there were no differences in density and age between medium and high intertidal. Given the results and the current knowledge on the effects of different factors influencing this species, we conclude that the distribution pattern and shell growth observed in our study reflect a response to metabolic necessities in combination with a strong influence of biological interactions. [ABSTRACT FROM AUTHOR]

Peptidoglycan recognition proteins (PGRPs) are indispensable molecules in innate immunity due to their prominent function in sensing and eliminating invading microorganisms. In the present study, a short type PGRP from razor clam Solen grandis (SgPGRP-S1) was recombinantly expressed and purified to investigate its potential function in innate immunity. As a pattern recognition receptor, recombinant SgPGRP-S1 (rSgPGRP-S1) specifically bind Lys-type and Dap-type peptidoglycan in vitro , but not lipopolysaccharide or β-glucan. The peptidoglycan binding ability of rSgPGRP-S1 resulted in significant agglutination activity against Gram-negative Escherichia coli and Listonella anguillarum , as well as Gram-positive Micrococcus luteus . Furthermore, rSgPGRP-S1 was bactericidal, significantly suppressing the growth of both E. coli and Gram-positive Staphylococcus aureus . The protein also exhibited strong amidase activity and degraded bacterial peptidoglycan in the presence of Zn 2+ , suggesting amidase activity might contribute to SgPGRP-S1 antibacterial activity. These results indicate SgPGRP-S1 is multifunctional in innate immunity, mediating both immune recognition and bacteria elimination. [ABSTRACT FROM AUTHOR]

Abstract: The effects of high hydrostatic pressure (HHP) treatments (200, 300, and 400 MPa for 1, 3, 5 and 10 min) on the shelling efficacy (the rate of shelling, the rate of integrity and yield of razor clam meat) and the physicochemical (drip loss, water‐holding capacity, pH, conductivity, lipid oxidation, Ca2+‐ATPase activity, myofibrillar protein content), microbiological (total viable counts) and microstructural properties of fresh razor clam (Sinonovacula constricta) were investigated. HHP treatments significantly (P < 0.05) increased shelling efficiency, water‐holding capacity, pH, conductivity, and lipid oxidation, and HHP‐treated razor clam showed lower levels of microorganisms and drip loss than untreated razor clam. Levels of thiobarbituric acid reacting substances (TBA) in HHP‐treated razor clam were greatly increased (up to 0.93 ± 0.09 mg MDA/kg at 400 MPa for 10 min) which was caused by the formation of hydroperoxides during HHP treatment. All HHP treatments were found to have adverse effects on the activity of Ca2+‐ATPase and the content of myofibrillar protein (MP), which might be due to the substantial damage to the tertiary structure of proteins at high pressure. Moreover, scanning electron microscopy (SEM) revealed the compaction of the muscle fibers and a decrease in the extracellular space with increasing pressure and holding time. This phenomenon was mainly correlated with the compaction of muscle fibers and denaturation, aggregation, and gelation of muscle protein triggered by high pressure. In general, HHP could be applied as a safe and effective nonthermal technology to produce high‐quality shelled razor clam. Practical application: High hydrostatic pressure (HHP) is now well known as a nonthermal processing technology and becoming increasingly acknowledged. However, it has not been widely applied to shell seafood due to its uncertain influence on its quality and shelling property. This study could provide valuable information regarding the shelling efficacy, physicochemical properties, and microstructure of razor clam treated by HHP. And it demonstrated that HHP showed a positive impact on quality of razor clam treated by HHP. [ABSTRACT FROM AUTHOR]

Aquaculture ponds represent a biogeochemical hotspot of the global carbon cycle. However, accurate estimations of their carbon budgets are hindered by a limited understanding of the temporal variability of carbon fluxes across time scales. In this study, the eddy covariance (EC) approach was applied to quantify net ecosystem CO 2 exchange (NEE) over algae-shellfish aquaculture ponds (razor clam cultivation) in Zhangjiang Estuary of Southeast China from January 2020 to June 2022, aiming to assess the diurnal variability of NEE during various management periods. The EC-based NEE over the ponds showed strong diurnal variations with daytime sink and nighttime source, mainly controlled by photosynthetically active radiation and air temperature, respectively. The ponds acted as a net sink system during razor clam (daily mean flux of −0.42 μmol m−2 s−1) and shrimp-crab (−0.50 μmol m−2 s−1) farming periods with a stronger daytime sink than a nighttime source, while it was the opposite during the drainage period acting as a net source (0.40 μmol m−2 s−1). The strength of sink/source also differed between the early and late stages of the razor clam farming period, with much larger (∼ 16 times) net carbon uptake in the late stage as a result of the strong daytime sink and near-neutral nighttime flux. The diurnal variability of NEE over the ponds was overall larger than other aquatic ecosystems and tended to increase with air temperature. Previous estimates of daily NEE from discrete daytime-only samplings might have biased the actual carbon budgets if no diurnal correction was applied in the temporal aggregation. The confirmed strong temporal variability of NEE across time scales highlighted the importance and necessity of continuous and high-frequency flux measurements in assessing the carbon budgets of algae-shellfish aquaculture ponds. • Strong diurnal variability of CO 2 fluxes over algae-shellfish aquaculture ponds. • Daytime-only measurements cannot represent all-day average of flux intensity. • First multi-year eddy covariance flux measurements over algae-shellfish ponds. • Aquaculture ponds are a CO 2 sink during razor clam and shrimp-crab periods. [ABSTRACT FROM AUTHOR]

Domoic acid (DA) is a neurotoxin that is naturally produced by phytoplankton and accumulates in seafood during harmful algal blooms. As the prevalence of DA increases in the marine environment, there is a critical need to identify seafood consumers at risk of DA poisoning. DA exposure was estimated in recreational razor clam ( Siliqua patula ) harvesters to determine if exposures above current regulatory guidelines occur and/or if harvesters are chronically exposed to low levels of DA. Human consumption rates of razor clams were determined by distributing 1523 surveys to recreational razor clam harvesters in spring 2015 and winter 2016, in Washington, USA. These consumption rate data were combined with DA measurements in razor clams, collected by a state monitoring program, to estimate human DA exposure. Approximately 7% of total acute exposures calculated (including the same individuals at different times) exceeded the current regulatory reference dose (0.075 mg DA·kg bodyweight − 1 ·d − 1 ) due to higher than previously reported consumption rates, lower bodyweights, and/or by consumption of clams at the upper range of legal DA levels (maximum 20 mg·kg − 1 wet weight for whole tissue). Three percent of survey respondents were potentially at risk of chronic DA exposure by consuming a minimum of 15 clams per month for at 12 consecutive months. These insights into DA consumption will provide an additional tool for razor clam fishery management. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate whether it is necessary to feed Solen marginatus (Pennánt, 1777) larvae externally and the evolution of fatty acids in the neutral and polar lipids during larval development in starved larvae and larvae fed on two different microalgal diets. Larvae were subjected to three different treatments: 1. 10 equivalent cells (Isochrysis galbana, Pavlova lutheri and Chaetoceros calcitrans) plus 20 equivalent cells of Tetraselmis suecica; 2. 80 equivalent cells of I. galbana and 3. starvation during eight days, and then individuals were re-fed on diet 1. The best results for growth were observed in larvae fed on diet 1. Starved larvae reached the best survival rate at day 8 (66%). However, three days after re-feeding all larvae died, suggesting that the “point of no return” was exceeded. In spite of the large size of S. marginatus eggs and the great amount of stored reserves, the larvae need to feed on microalgae to undergo metamorphosis. Non-methyle-interrupted dienoic fatty acids and their precursors 16:1n-7 and 18:1n-9 are of great importance in starved larvae. Saturated fatty acids, especially 16:0, fuel larval development. A certain degree of bioconversion of 18:2n-6 to 20:4n-6 was observed in S. marginatus larvae.

Sedentary filter-feeders such as the razor clam (Solen cylindraceus) are believed to indiscriminately exploit a carbon source derived from particulate organic matter (POM). POM demonstrates a high degree of spatial and temporal variability in composition, which may result in intraspecific dietary variation. This study aimed to investigate seasonal ontogenetic shifts in the feeding ecology of S. cylindraceus using dual stable isotopic (δ13C and δ15N) analyses in the oligotrophic temperate permanently open Kariega Estuary, South Africa. Mixing model results demonstrate that the different size classes of S. cylindraceus had a diet comprised mainly of POM. However, size grouping did have a significant effect on carbon and nitrogen signatures. Specifically, during winter, carbon isotopic signatures became more depleted with a decrease in size, while both winter and summer δ15N values became more nitrogen enriched with an increase in size. The observed trend in the ratios can likely be ascribed to the hydrodynamics of the system. Data from this study suggest that there may be some degree of variation among the different size cohorts, although this needs further investigation. [ABSTRACT FROM AUTHOR]

Three Tribal Nations in the Pacific Northwest United States comprise the members of the CoASTAL cohort. These populations may be at risk for neurobehavioral impairment, i.e., amnesic shellfish poisoning, from shellfish consumption resulting in repeated, low-level domoic acid (DA) exposure. Previous work with this cohort confirmed a high proportion of clam consumers with varying levels of potential exposure over time. Since clams are an episodically consumed food, traditional dietary records do not fully capture exposure. Frequency questionnaires can capture accumulated doses over time and this data can be used to examine dose–response relationships with periodic studies of memory and learning. However, frequency questionnaires cannot be used to assess consumption and memory response in real time. To address this shortcoming, a modified technology assisted dietary assessment (TADA) iPod application was developed to capture images of the clam meal, sourcing data, and associated memory functioning within 24 h and seven days after consumption. This methodology was piloted with razor clam meals consumed by members from the CoASTAL cohort. Preliminary findings suggest that the TADA iPod application is potentially useful in collecting real-time data with respect to razor clam consumption, as well as one day and seven day memory outcome data. This technology holds promise for addressing the challenges of other HAB related dietary exposure outcome studies. [ABSTRACT FROM AUTHOR]

Angiotensin I-converting enzyme (ACE) inhibitory activity of razor clam hydrolysates produced using five proteases, namely, pepsin, trypsin, alcalase, flavourzyme and proteases from Actinomucor elegans T3 was investigated. Flavourzyme hydrolysate showed the highest level of degree of hydrolysis (DH) (45.87%) followed by A. elegans T3 proteases hydrolysate (37.84%) and alcalase (30.55%). The A. elegans T3 proteases was observed to be more effective in generating small peptides with ACE-inhibitory activity. The 3 kDa membrane permeate of A. elegans T3 proteases hydrolysate showed the highest ACE-inhibitory activity with an IC50 of 0.79 mg/mL. After chromatographic separation by Sephadex G-15 gel filtration and reverse phase-high performance liquid chromatography, the potent fraction was subjected to MALDI/TOF-TOF MS/MS for identification. A novel ACE-inhibitory peptide (VQY) was identified exhibiting an IC50 of 9.8 μM. The inhibitory kinetics investigation by Lineweaver-Burk plots demonstrated that the peptide acts as a competitive ACE inhibitor. The razor clam hydrolysate obtained by A. elegans T3 proteases could serve as a source of functional peptides with ACE-inhibitory activity for physiological benefits. [ABSTRACT FROM AUTHOR]

Dredge fisheries for benthic bivalves are among the most destructive in Europe. Other options such as electrofishing may be more sustainable, although this fishing method is currently illegal under EU law. Electrofishing trials conducted under an EU derogation in the dover sole and Crangon fisheries, have been shown to increase selectivity and reduce the detrimental effect of fishing on the viability of non-target benthic species. Illegal electrofishing for razor clams Ensis spp., has been reported in Scottish waters since 2004. Whilst the effects of this electrofishing on non-target species and the environment where razor clams live are poorly understood, it could present a potentially lower impact method of harvesting razor clams than conventional dredge fisheries. This study uses both tank experiments and direct observation in the field to assess the vulnerability of a range of vertebrate and invertebrate non-target species to electrofishing. The field properties of the AC electrical stimulus commonly used in the fishery are also recorded for the first time. Both tank experiments and sea trials indicated that behavioural changes induced by the electric field were temporary, lasting for a maximum of 8 min (median = 3 min 37 s) across all species tested. Tank trials involving Ensis and three other non-target species were unable to reveal a significant difference in survival when comparing control against electrically fished individuals. Physical impacts of the fishing gear on the seabed were minimal, presenting a lower impact on the environment than current fishing methods. Our results confirm that electrofishing is a low impact method of harvesting Ensis spp., however due to its high catch efficiency the regulation of fishing effort may be required to ensure a sustainable fishery. [ABSTRACT FROM AUTHOR]

Ensis macha is a razor clam distributed throughout the coasts of southern Argentina and Chile. Even though it represents a valuable fishery resource, the exploitation of its Atlantic populations has begun only in recent years. This study provides the first estimates of growth rate, an interpretation of the reproductive cycle on the coast of the northern Argentine Patagonia and an analysis of the species morphometry. Growth was estimated by direct observation of growth rings on the valves by two observers. The reproductive cycle was interpreted by the analysis of temporal change of oocyte size frequency distributions. Parameter estimations for the von Bertalanffy equations respectively obtained by observers 1 and 2 were 154 and 153.7 mm for L?, 0.25 and 0.20 yr-1 for k, and -0.08 and -0.72 yr for t0. Two spawning peaks were detected: September-November 1999 and May-June 2000. However, mature females were found all year round. An abrupt change in the relationship between shell length and height was detected at 11.2 mm length.

Knowledge of the biology of economically important marine resources is essential in fisheries management. However, the methodologies developed by scientists are usually not applicable for assessing small-scale fisheries (SSFs), as they are too complicated and/or too costly. Classic methodologies taken from industrial fisheries are usually very data demanding and need of highly specialized personnel in modelling and stock assessment; both things are usually not present in most of the small-scale fisheries. In Galicia, shellfishing (that could be considered as SSFs) is an important economic and social activity that is co-managed between the Autonomous Administration (Xunta de Galicia) and 63 fishers’ guilds (called “cofradías de Pescadores”). Most guilds count with a Technical Assistant in Shellfisheries Management (TA), that serves as liaison between fishers, managers and scientists and is in charge of designing, implementing and supervising management plans (Macho et al., 2013). However, these experts count with scarce time and limited resources, being necessary simple assessment and management procedures. The present work aims to provide easy tools to monitor the species biology in order to incorporate it in the daily fishery management. We took as a model the sword razor clam (Ensis magnus (Schumacher, 1817), syn. E. arcuatus (Jeffreys, 1865)) because despite being the most important commercial species of Solenidae in Europe and one of the most important shellfisheries in Galicia (370 t in 2013) (http://pescadegalicia.com. accessed 4 January 2013), little is known about its biology. Furthermore, the fishers and the TAs from Galicia have observed some problems that could be related to the biology of the species. The most important one is that harvested razor clams break by the foot in a high proportion during winter, which could lead to a loss of up to 30-40% of the catch since these individuals have to be discarded. In the light of these problems, the specific objectives of this work were 1) to carry out mesoscale studies (~10 km) of the reproductive biology in order to adapt the possible variability to the management strategy (rotation scheme and reproductive close season), 2) to estimate the size at first maturity, 3) to construct a simple tool to easily monitor the gonad development stage of the resource, 4) to determine the cause of the foot breakage in order to reduce it as much as possible, 5) to study the spatial variability in recruitment for evaluate whether should be established seasonal closures for fishing in areas/periods where recruitment is more intense, 6) to ascertain which method was the most efficient in estimating the age of this species (counting external shell rings by eye vs acetate peels of the internal shell microstructure) and to test the possibility of using external rings as an easy management tool and 6) to evaluate the growth variability throughout the ria. To achieve the presented objectives, different samplings were conducted between 2008 and 2011 in three fishing beds of the Ría de Pontevedra (Galicia, NW Spain) (Brensa, Bueu and Ons located at the inner, middle and outer part of the ria) by scuba-diving at depths between 5 and 15 m. Thus, 20 samples of E. magnus were collected fortnightly/monthly during two years in order to study reproduction using the four following methodologies: gonad coverage (established by visually determining the percentage of coverage of the gonad), gonad smear (a new scale was created describing the follicles), gonadal condition index (GCI: gonad fresh weight/dry shell weight) and histology. The proportion of broken clams was recorded by the divers. Besides, 113 sites separated 50 m between them and distributed throughout the main beds of the ria were sampled by scuba diving in the shallower points and using a box corer in the deeper ones. The collected sand was sieved and processed by binocular microscope to calculate the recruit (size < 2cm) density at each site. Finally, 110 samples were collected in each bed to estimate the age. The reproductive cycle was characterized by a resting stage during summer and early autumn, initiation of gametogenesis in autumn and a period of successive spawning interspersed with gonad recovery during winter and spring (Fig. 1). However, differences in the reproductive cycle were detected between study sites. Thus, a 15-day to one month delay in advanced stages of gametogenesis and maturation was observed between the inner and the outermost fishing beds of the ria, as well as an extended spawning period in the outermost bed. In view of these results, the razor clam fishery in the Ría de Pontevedra has adapted the rotation scheme to the reproductive cycle, moving the harvesting from the inner to the outer bed during the maturation period and from the outer to the inner bed at the end of the spawning period. Size at first maturity was determined in 79 mm, lower than the commercial size established for the species (100 mm). A simple tool to monitor the razor clam gonad development stage was created based on a correspondence table which linked the easiest and fastest reproductive study methods (gonad coverage and gonad smear) to the most accurate but more time consuming methods (GCI and histology). Gonad coverage was confirmed as a good descriptor of the reproductive cycle of the sword razor clam because it changed considerably along the sexual development, following exactly the same evolution as the GCI used. Moreover, the gonad smear could be used to identify the maturation period, complementing the gonad coverage method. Using these methods, the reproductive stage of the razor clams could be monitored by TAs. Besides, a relationship between gonadal development and the proportion of broken razor clams was observed as most broken razor clams appeared during maturity, postspawning and gonad recovery (Fig. 1). This information could be incorporated in the daily management of the fishery since the Galician harvesting plans allows adaptive management according to stock characteristics, such as the reproductive state, at any time (Fig. 2). Monitoring the gonad development stage could prevent the highest razor clam breakage and contribute to reduce as much as possible the discards. Although the razor clam recruits were not easily found due to the burrowing behaviour and the final recruitment density was too low (average of 120 recruits per m2) to explain the razor clam production (34 adults per m2), the recruitment was higher (390 recruits per m2) at the shallowest points of the innermost bed of Brensa. The acetate peel technique proved to be the most suitable method for growth estimate and equivalence between methods is not possible (Hernández Otero et al. 2014). Following the acetate peel method, the growth of E. magnus is faster during the first three years of life, declines at about four–six years old and almost ceases in subsequent years, with the organisms entering into an asymptotic phase around the age of eight-nine years (Fig. 3). The mean population length is attained at four-five years. As observed by the fishers, growth differences were found between beds with the slower growth observed in the middle area (L∞ = 140.4, k = 0.40) followed by the innermost one (L∞ = 151.91, k = 0.40) and the outermost one (L∞ = 172.7, k = 0.33) reaching commercial size in 2.8, 2.3 and 1.7 years respectively. Some of the findings of the present study are being applied since 2011 in the razor clam fishery of the Ría de Pontevedra leading to a more efficient and sustainable exploitation and contributing to its certification as a sustainable fishery by the Marine Stewardship Council (MSC). Fig. 1 Temporal distribution of gametogenic stages of E. magnus and variation in the proportion of broken clams (black) at Brensa throughout the study period. Histological stages: (0) sexual resting, (1) start of gametogenesis, (2) advanced gametogenesis, (3) maturity, (4A) postspawning, (4B) gonad recovery and (5) exhaustion. Foot breakage degree: (0) No broken razor clams, (1) less than 20% of broken razor clams, (2) 20 to 40% of broken razor clams, (3) 40 to 60% of broken razor clams, (4) 60% to 80% of broken razor clams and (5) more than 80% of broken razor clams. Fig. 2. Management procedure proposed. Dark grey polygons indicate the stakeholders involved in shellfishing. Light grey polygons and white boxes show the recommended management actions. Fig. 3 von Bertalanffy growth curves fitted for E. magnus using growth marks revealed in the acetate peels.

The population genetic structure of the razor clam Sinonovacula constricta was investigated between populations collected from China, Korea and Vietnam using cytochrome oxidase subunit 1 (COI) mtDNA and internal transcribed spacer 2 (ITS2) rDNA markers. A total of 622 bp of COI and 495 bp of ITS2 were sequenced. Highly significant Fst values and low rates of migration were observed from populations between Vietnam and China, (Fst = 0.7578, P < 0.001, Nm = 0.05 for COI; Fst = 0.91389, P < 0.001, Nm = 0.07 for ITS2) and Korea (Fst = 0.79783, P < 0.001, Nm = 0.07 for COI; Fst = 0.74143, P < 0.001, Nm = 0.03 for ITS2). However, lower Fst values and higher gene flow were detected between populations from China and Korea (Fst = 0.25733, P < 0.001, Nm = 0.73) based on COI analysis. The similar pattern was also captured by ITS2 rDNA marker. In addition, Neighbor-joining phylogenetic tree analysis of the two markers resulted in one cluster consisting of haplotypes from Vietnam, and a second group comprising haplotypes from China and Korea. This research revealed a closer genetic relationship between clam population from China and Korea but less similarity to population from Vietnam. [ABSTRACT FROM AUTHOR]

Few studies have been conducted on the temporal dynamics of both amino acid (AA) and fatty acid (FA) profiles in marine bivalves. We investigated the seasonal variation of these compounds in the pod razor clam Ensis siliqua in relation to food availability, salinity, water temperature and reproductive cycle. AA content varied between 46.94 and 54.67 % dry weight (DW), and the AAs found in greater quantity were glutamic acid, glycine and aspartic acid. FA content varied between 34.02 and 87.94 mg g DW and the FAs found in greater quantity were 16:0 and 22:6 n-3. Seasonal trends were observed for AAs and FAs. FAs increased with gametogenesis and decreased with spawning while AA content increased throughout spawning. The effect of increasing temperature and high food availability during the spawning season masked the loss of AAs resulting from gamete release. Still, a comparatively greater increase in the contents of glutamic acid and leucine with spawning indicate their possible involvement in a post-spawning gonad recovery mechanism. A post-spawning decrease in 14:0, 16:0, 16:1 n-7, 18:1 n-7 and 18:1 n-9 is indicative of the importance of these FAs in bivalve eggs. An increase in 18:3 n-3, 18:4 n-3, 20:1 n-9 and 20:2 n-6 during gametogenesis suggests their involvement in oocyte maturation. The FA 22:4 n-6, while increasing with spawning, appears to play a role in post-spawning gonad recovery. Salinity did not have an effect on the AA composition. None of the environmental parameters measured had an effect on FA composition. [ABSTRACT FROM AUTHOR]

Abstract: Mesoscale differences in the reproductive cycle of the commercial sword razor clam Ensis magnus (Schumacher, 1817) were studied in six shellfish beds in the Ría de Pontevedra (NW Spain) between March 2008 and July 2010. The GCI accurately described the reproductive cycle as indicated by the histological analysis. Both methods showed that the reproductive cycle was similar at different sites and was characterized by a resting stage during summer and early autumn, initiation of gametogenesis in autumn and a period of successive spawning interspersed with gonad recovery during winter and spring. However, a 15-day to one month delay in advanced stages of gametogenesis and maturation was observed between the inner and the outermost site of the ria, as well as an extended spawning period in the outermost area. Lower bottom seawater temperatures at the outermost sites appeared to delay maturation and to prolong the spawning periods, whereas salinity fluctuations at the innermost sites appeared to reduce the length of the cycle. This study provides the first estimation of the size at which E. magnus reaches sexual maturity in the Iberian Peninsula, determined in 79mm, and it is also the first work in determining the mesoscale variation in gonadal development of any species of the superfamily Solenoidea. The results highlight the importance of carrying out mesoscale studies of the reproductive biology in coastal fisheries resources. Some of the findings of the present study have already been applied in the rotation scheme of the fishery harvesting plan. [Copyright &y& Elsevier]

Hatchery culture of the razor clam, Solen marginatus (Pulteney), has recently been developed in Galicia ( NW Spain). However, recurrent episodes of mortalities of larval and post-larval cultures have been recorded during the course of various studies. The disease signs were similar to those described for other bivalve species in outbreaks caused by bacteria of the genus Vibrio. In this article, we present the results of microbiological monitoring of two batches of razor clams with different survival rates. All fermentative isolates were identified as members of the Splendidus clade within the genus Vibrio. Some of these isolates, identified as Vibrio splendidus-like, were clearly associated with the batch suffering mortalities, indicating their possible role as pathogens. Similar strains were found in the broodstock, suggesting vertical transmission of these bacteria. This is the first study of the microbiota associated with hatchery culture of S. marginatus, and the results will provide useful information for the optimization of a protocol for hatchery culture of this bivalve species. [ABSTRACT FROM AUTHOR]

This article reports on the changes in gross biochemical and fatty acid composition of the razor clam Ensis arcuatus larvae throughout development. Protein was the largest component of dried larval tissues. The energy required for embryogenesis in E. arcuatus oocytes was obtained from stored proteins and carbohydrates, while total lipids increased significantly. Lipids and carbohydrates have an important role as energy contributors from day 1 to day 8. During larval development the strategy was to indistinctly store energy reserves (protein, lipid and carbohydrate) to surpass metamorphosis. During embryonic development there was a gain in fatty acids of neutral and polar lipids. A depletion of fatty acids in neutral lipids was observed from day 1 to day 8 in E. arcuatus larvae, mainly due to the decrease in 16:0 and EPA. NMID fatty acids were present in amounts similar to those of some PUFAs in polar lipids, especially 22:2 NMID. [ABSTRACT FROM AUTHOR]

Abstract: Laboratory experiments were carried out with Ensis directus to estimate clearance rate and growth rate as a function of the amount of food and presence of silt. Two food levels were tested: low food availability (6.5μg chla/l) and high food availability (16.5μg chla/l) at four silt concentrations (0, 50, 150 and 300mg/l). Clearance rates of E. directus varied between 0.7 and 5.9l/h/g DW. At a silt concentration of 300mg/l clearance rates were significantly lower (16–56%) than rates at 150mg/l, 50mg/l and 0mg/l silt. This indicates that only the highest silt concentration induced a reduction in clearance rate. The tested food levels did not influence the clearance rate of E. directus. Maximum growth rate of E. directus was 0.24mm increase in shell length and 2% increase in wet weight per day. Long-term (10weeks) exposure to silt concentrations of 300mg/l showed significantly higher growth than the 150mg/l treatment. This indicates that exposure to a high silt concentration did not induce a reduction in growth, but stimulated growth. Long-term (10weeks) exposure to a food level of 6.5μg chla per litre reduced the shell growth of E. directus with 40% compared to growth at 16.5μg chla per litre. The laboratory experiments suggest that E. directus is more sensitive to a reduction in algal concentration than to an increase in silt concentration. [Copyright &y& Elsevier]

This study investigated razor clam Ensis arcuatus culture from larval rearing to commercial size to assess it's aquaculture potential. Broodstock was spawned several times in hatchery facilities to demonstrate that larval availability is not a constraint for hatchery production. Larval culture lasted 20 days, showing an average survival of 14.35%. The razor clam seed reached a size of 28.5 mm at 4 months. Seed culture is feasible; however, it is constrained by the fact that razor clams need to be buried. Higher survival was observed when culturing razor clam seed with a substrate (82-83%), irrespective of the substrate grain size, while containers held without a substrate showed a significantly lower survival (56.5%). We showed that it is possible to rear E. arcuatus juveniles in bottles, with survival as high as 94-95% being achieved. The length increase of the hatchery-produced E. arcuatus over 600 days was described by the equation Ln L=4.5+(−141.17/ t), where L is length in mm and t is time in days. On-growing showed adequate survival rates and it took 2-3 years to reach commercial size. [ABSTRACT FROM AUTHOR]

The genetic variation and differentiation of the razor clam Sinonovacula constricta distributed along the coast of China were studied through amplified fragment length polymorphism (AFLP) analysis. Six primer combinations generated 193 fragments. The He values varied from 0.322 to 0.463 and the percentage of polymorphic loci ranged from 74.1% to 98.4%, which indicates a high level of genetic diversity. Cluster analysis by Nei’s pairwise distance grouped all specimens by geographical origins. AMOVA consistently showed that genetic variation among populations was 8.71%, and most of the variation came from the genetic variation within populations (91.29%). Genetic differentiation among the six populations was moderate; pairwise FST ranged from 0.0282 to 0.1480, which indicated that S. constricta populations along the coast of China are genetically connected. Among all the six populations, the Beihai population is the mostly differentiated from the others, suggesting that Hainan Island and Leizhou Peninsula act as barriers to gene flow. All populations abide isolation by distance model as indicated by Mantel test, except for ZS (Zhoushan) and YQ (Yueqing) populations. Information obtained in this study will provide guidelines for conservation and fishery management of this species in the future. [ABSTRACT FROM AUTHOR]

Abstract: Symbionts and abnormal conditions of razor clam Ensis arcuatus were surveyed in three commercially important natural beds of Galician estuaries (NW Spain). Samples of 15–20 E. arcuatus were collected every 2months from January 2003 until July 2004 and processed for histological examination. Prokaryote-like colonies, renal coccidians, gregarines, Trichodina sp. ciliates, haplosporidian-like plasmodia, turbelaria, trematode metacercariae, cestode-like larvae and basophilic inclusion bodies were observed in razor clam tissues without causing host damage. Bucephalid digenean sporocysts and germinoma were seen in some samples causing moderate or severe damage to the host depending on the intensity of infection and both could be a cause for concern if prevalence reached epizootic levels in Galician E. arcuatus populations. None of the parasites detected is OIE notifiable and, in general, the commercially exploited beds studied seem to be devoid of serious pathogens. [Copyright &y& Elsevier]

Abstract: A specific multiplex polymerase chain reaction (PCR) was applied to differentiate samples of razor clams Ensis arcuatus, Ensis siliqua, Ensis directus, and Ensis macha. Universal primers were used for the amplification of internal transcribed spacer 1 (ITS-1) in each species. The alignment of the obtained sequences was the basis for the specific design of species-specific reverse primers (ITSArSil-R, ITSDir-R, and ITSMa-R) located in the ITS-1 region. A multiplex PCR using each specific primer together with a common forward primer allowed identification of razor clam species by means of the different sizes of the species-specific amplicons separated in an agarose gel electrophoresis. This work provides a simple, reliable and rapid protocol for the accurate identification of Ensis species. The present methodology can be very useful for traceability of the species and to reinforce labelling regulations. [Copyright &y& Elsevier]

For a study of 5S ribosomal genes (rDNA) in the razor clam Ensis macha, the 5S rDNA region was amplified and sequenced. Two variants, so-called type I or short repeat (~430 bp) and type II or long repeat (~735 bp), appeared to be the main components of the 5S rDNA of this species. Their spacers differed markedly, both in length and nucleotide composition. The organization of the two variants was investigated by amplifying the genomic DNA with primers based on the sequence of the type I and type II spacers. PCR amplification products with primers EMLbF and EMSbR showed that the long and short repeats are associated within the same tandem array, suggesting an intermixed arrangement of both spacers. Nevertheless, amplifications carried out with inverse primers EMSinvF/R and EMLinvF/R revealed that some short and long repeats are contiguous in the same tandem array. This is the first report of the coexistence of two variable spacers in the same tandem array in bivalve mollusks. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize new microsatellite loci in the razor clam Ensis arcuatus (Bivalvia: Pharidae) and examine the temporal genetic variability of a natural bed in Cies Islands (Galicia, north-western Spain) exploited by apnoea divers and affected by the ‘Prestige’ oil tanker spill in November 2002. In this work, we characterized four polymorphic microsatellites using an alternative approach that relies on the amplification and sequencing of ISSR markers. Observed heterozygosities ranged from 0.1053–0.6800 and number of alleles from 4–19. Linkage equilibrium was observed in all loci and two of them showed significant deviations from Hardy–Weinberg equilibrium. Estimators of FST between samples were low (<0.05) and not different from zero with a confidence level of 5%. We did not detect a clear decreasing tendency in genetic diversity although we found a significant change in allelic frequencies among samples (P = 0.0024) after the ‘Prestige’ oil spill. We propose that both phenomena could be related to a high variance in genetic success and/or a movement of adults or larvae from different source populations. [ABSTRACT FROM PUBLISHER]

The association of DNA with histones results in a nucleoprotein complex called chromatin that consists of repetitive nucleosomal subunits. Nucleosomes are joined together in the chromatin fiber by short stretches of linker DNA that interact with a wide diversity of linker H1 histones involved in chromatin compaction and dynamics. Although the long-term evolution of the H1 family has been the subject of different studies during the last 5 years, the lack of molecular data on replication-independent (RI) H1 variants from protostomes has been hampering attempts to complete the evolutionary picture of this histone family in eukaryotes, especially as it pertains to the functional specialization they impart to the chromatin structure in members of this bilaterian lineage. In an attempt to fill this gap, the present work characterizes the histone gene complement from the razor clam Solen marginatus. Molecular evolutionary analyses reveal that the H1 gene from this organism represents one of the few protostome RI H1 genes known to date, a notion which is further supported by its location within the monophyletic group encompassing the RI H1 variants in the overall phylogeny of eukaryotic H1 proteins. Although the detailed characterization of the nucleotide substitution patterns in RI H1 variants agrees with the model of birth-and-death evolution under strong purifying selection, maximum-likelihood approaches unveil the presence of adaptive selection during at least part of the evolutionary differentiation between protostomes and deuterostomes. The presence of increased levels of specialization in RI H1 proteins from deuterostomes as well as the significant differences observed in electrostatic properties between protostome and deuterostome RI H1s represent novel and important preliminary results for future studies of the functional differentiation of this histone H1 lineage across bilaterians. [ABSTRACT FROM AUTHOR]