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The northern quahog (Mercenaria mercenaria) supports lucrative aquaculture industries in the USA. In the southeastern USA, aquacultured M. mercenaria faces increasing risks of summer die-offs from prolonged heat waves. We used a comparative transcriptomic approach to investigate the molecular responses of M. mercenaria and its southern congener, Mercenaria campechiensis, to controlled incremental heat stress over a 4-week period. Mercenaria were exposed to temperatures from 24 to 34 °C with 2.5 °C/week, after which, gill transcriptomes were de novo assembled and annotated. During the 4 weeks of chronic heat exposure, both species had the same survival rate (96%); M. mercenaria experienced body weight gain/loss depending on the originated hatcheries while M. campechiensis experienced an average net weight loss. The upregulated genes in both species included those in chaperone-mediated protein folding and regulation of cell death pathways, while the downregulated genes in both species involved in mRNA processing and splicing pathways. Compared to M. mercenaria, M. campechiensis appears to be more sensitive to prolonged heat stress as indicated by upregulating significantly more genes in coping with oxidative stress and in the protein degradation pathways, while downregulating some inhibitors of apoptosis. We discussed this finding within their ecological and evolutionary context. Our findings highlighted the potential vulnerability of the two quahogs, especially the southern quahog, to continued ocean warming.

The northern quahog Mercenaria mercenaria (commonly named hard clam) is an important aquaculture and fishery species along the Atlantic west coast. Environmental stresses, such as heat shock, fluctuating salinity, and harmful algal blooms are major challenges for clam aquaculture. In response to environmental stresses, hemocytes would change dynamically for defense and immunity. The goal of this study was to characterize basic immunological assays of hemocytes in the northern quahog by use of flow cytometry. The objectives were to: 1) develop a non-lethal method for hemolymph collection and dilution; 2) verify the capability of flow cytometry for hemocyte count and type identification through comparison with microscopic observation; 3) validate hemocyte viability assay based on plasma membrane integrity, and 4) develop hemocyte phagocytosis assay by use of fluorescein labeled microbeads. A non-lethal hemocyte collection method was developed using needle insertion through the ligament. Osmolality measurement of serum was the same as that of culture seawater. The pH measurement of serum (7.2) was significantly different from that of culture seawater (8.4). By microscopic observation, three types of hemocytes were identified with granulocytes, the dominant cell type (70 ± 16%), agranulocyte (14 ± 4%), and blast-like cell (16 ± 4%), and no differences were found from the measurements by flow cytometer on FSC/SSC plot (cell size/granularity). The viability of hemocytes based on plasma membrane integrity was 88 ± 6% ranging from 70 to 97% (n = 60, three populations), and viability protocol was further validated with the pre-set expected viability (p ≥ 0.424). Phagocytosis assay of hemocytes with fluorescence beads showed a mean capacity of 10 ± 5% (n = 60, three populations). Incubation time (up to 6 h) or bead concentrations (2:1 or 5:1 to hemocytes) did not affect the phagocytosis measurement. Overall, this study reported the basic characteristics of hemolymph (serum and hemocytes) of northern quahogs. It is expected that the assay methodologies will be applied to evaluation of hemocyte responses to environmental stresses for clam aquaculture.

Ongoing inputs, in the form of sediment deposition along with associated dissolved contaminants, have challenged the assessment of cap performance at contaminated sediment sites. To address this issue, thin 2–3 cm layer sand caps amended with activated carbon (AC) were investigated for the remediation of polychlorinated biphenyl (PCB) contaminated marine sediments using 90-day mesocosms. All treatments were challenged with (1) ongoing clean or marker-PCB-spiked sediment inputs and (2) bioturbation. Bioaccumulation in hard clams (filter feeding near the cap-water interface) was evaluated to best understand cap effectiveness, relative to sheepshead minnows (confined to the surface water) and sandworms (which burrowed through the caps). All caps (sand and AC amended sand) provided isolation of native bedded PCBs (i.e., PCBs sourced from the bed), reducing uptake in organisms. Total PCB bioaccumulation in clams indicated that AC addition to the cap provided no benefit with spiked influx, or some benefit (56% reduction) with clean influx. Spiked input PCBs, when added to the depositional input sediment, were consistently detected in clams and passive samplers, with and without AC in the cap. PCB uptake by passive samplers located in the caps did not reflect the performance of the remedy, as defined by clam bioaccumulation. However, PCB uptake by passive samplers in the overlying water reasonably represented clam bioaccumulation results.

Intertidal bivalves are constantly exposed to air due to daily and seasonal tidal cycles. The hard clam Mercenaria mercenaria is an economically important bivalve species and often subjected to air exposure for more than 10 days during long-distance transportation. Hard clam exhibits remarkable tolerance to air exposure. In this study, we performed RNA sequencing on hemocytes of M. mercenaria exposed to air for 0, 1, 5, 10, 20 and 30 days. The overall and dynamic molecular responses of hard clams to air exposure were revealed by different transcriptomic analysis strategies. As a result, most cytochrome P450 1A and 3A, and monocarboxylate transporter family members were up-regulated during air exposure. Additionally, the dominant molecular process in response to 5-d, 10-d, 20-d and 30-d air exposure was refolding of misfolded proteins in endoplasmic reticulum, lysosome-mediated degradation of phospholipids , protein metabolism and reorganization of cytoskeleton , and activation of anti-apoptotic process, respectively. Our results facilitated comprehensive understanding of the tolerance mechanisms of intertidal bivalves to air exposure.

Background P-selectin is a molecule participating in the inflammatory response through mediating cellular adhesion and essential for wound repair. However, studies regarding P-selectin in Bivalvia are rare. This study identified 90 P-selectin genes among nine bivalve genomes and classified them into 4 subfamilies according to phylogenetic analysis. Results Notable P-selectin gene expansion was observed in two Venerida species, Sinonovacula constricta and Mercenaria mercenaria. The synteny analysis revealed that P-selectin gene expansion was mostly caused by tandem duplication. In addition, the expression profiles of P-selectin genes in S. constricta showed that many P-selectins were specifically highly expressed in the gills, and the P-selectin expression patterns changed dramatically under low salt stress and ammonia nitrogen stress. Conclusions The massive expansion of P-selectins may facilitate the tolerance to environmental stresses. This study sheds light on the characterizations and expression profiles of P-selectin genes in Bivalvia and provides an integrated framework for further investigation of the role of P-selectins in the environmental tolerance of bivalves.

Lipases form an important group of relevant enzymes which have applications in various fields including; food, pharmaceutical, detergent, textile and cosmetic industries. Lipases can be produced from diverse sources including microorganisms. This study evaluated the potential of bacteria isolates from fresh-water clam Mercenaria Mercenaria to produce lipolytic enzymes. Ten samples of Clam (Mercenaria Mercenaria) were screened for the presence of lipase producing bacteria using classical culture methods. Eleven bacteria species were obtained, of which six (Actinomyces sp., E. coli, Bacillus sp., Pseudomonas sp., Clostridium sp. and Klebsiella sp.) produced lipases that had lipolytic activity in breaking down olive oil used in media supplementation. The best culture media and conditions for optimal production of lipases was studied and it was shown that supplementation of growth media with 2% dextrose at neutral pH gave the greatest yield of lipases when lipase producing isolates were grown in shake flasks. Measurement of biomass by culture and turbidimetric methods indicates that the highest cell mass was recorded by Pseudomonas sp at 7.8 x 105 CFU/ml, closely followed by Actinomyces sp. and Bacillus sp., at 6.2 x 105 CFU/ml and 5.3 x 105 respectively. The produced lipases were partially purified by precipitating with ammonium sulphate followed by dialysis. The total protein content of produced lipases was evaluated by the Lowry’s method, showing that estimated protein content followed the same trend as cell biomass with the highest recorded by Pseudomonas sp. at 1.53mg/ml, followed by Actinomyces sp. and Bacillus sp. at 1.47mg/ml and 1.32mg/ml respectively. The results obtained in this study shows that isolates obtained from freshwater clam can produce potent lipases which can be employed for industrial, food and other diverse uses

Severe losses in aquacultured and wild hard clam (Mercenaria mercenaria) stocks have been previously reported in the northeastern United States due to a protistan parasite called QPX (Quahog Parasite Unknown). Previous work demonstrated that clam resistance to QPX is under genetic control. This study identifies single nucleotide polymorphism (SNP) associated with clam survivorship from two geographically segregated populations, both deployed in an enzootic site. The analysis contrasted samples collected before and after undergoing QPX-related mortalities and relied on a robust draft clam genome assembly. ~200 genes displayed significant variant enrichment at each sampling point in both populations, including 18 genes shared between both populations. Markers from both populations were identified in genes related to apoptosis pathways, protein-protein interaction, receptors, and signaling. This research begins to identify genetic markers associated with clam resistance to QPX disease, leading the way for the development of resistant clam stocks through marker-assisted selection.

The aim of the present investigation is to develop mechanochemically synthesized nano-crystalline hydroxyapatite (nHAp) bioceramics using clam seashells and phosphoric acid by varying the CaO:H3PO4...

With marine diseases on the rise and increased reliance on molecular tools for disease surveillance, validated pathogen detection capabilities are important for effective management, mitigation, and response to disease outbreaks. At the same time, in an era of continual evolution and advancement of molecular tools for pathogen detection, it is critical to regularly reassess previously established assays to incorporate improvements of common practices and procedures, such as the minimum information for publication of quantitative real-time PCR experiments (MIQE) guidelines. Here, we reassessed, re-optimized, and improved the quantitative PCR (qPCR) assay routinely used for Quahog Parasite Unknown (QPX) disease monitoring. We made 19 significant changes to the qPCR assay, including improvements to PCR amplification efficiency, DNA extraction efficiency, inhibition testing, incorporation of linearized standards for absolute quantification, an inter-plate calibration technique, and improved conversion from copy number to number of cells. These changes made the assay a more effective and efficient tool for disease monitoring and pathogen detection, with an improved linear relationship with histopathology compared to the previous version of the assay. To support the wide adoption of validated qPCR assays for marine pathogens, we provide a simple workflow that can be applied to the development of new assays, re-optimization of old or suboptimal assays, or assay validation after changes to the protocol and a MIQE-compliant checklist that should accompany any published qPCR diagnostic assay to increase experimental transparency and reproducibility amongst laboratories.

Background The hard clam Mercenaria mercenaria is a major marine resource along the Atlantic coasts of North America and has been introduced to other continents for resource restoration or aquaculture activities. Significant mortality events have been reported in the species throughout its native range as a result of diseases (microbial infections, leukemia) and acute environmental stress. In this context, the characterization of the hard clam genome can provide highly needed resources to enable basic (e.g., oncogenesis and cancer transmission, adaptation biology) and applied (clam stock enhancement, genomic selection) sciences. Results Using a combination of long and short-read sequencing technologies, a 1.86 Gb chromosome-level assembly of the clam genome was generated. The assembly was scaffolded into 19 chromosomes, with an N50 of 83 Mb. Genome annotation yielded 34,728 predicted protein-coding genes, markedly more than the few other members of the Venerida sequenced so far, with coding regions representing only 2% of the assembly. Indeed, more than half of the genome is composed of repeated elements, including transposable elements. Major chromosome rearrangements were detected between this assembly and another recent assembly derived from a genetically segregated clam stock. Comparative analysis of the clam genome allowed the identification of a marked diversification in immune-related proteins, particularly extensive tandem duplications and expansions in tumor necrosis factors (TNFs) and C1q domain-containing proteins, some of which were previously shown to play a role in clam interactions with infectious microbes. The study also generated a comparative repertoire highlighting the diversity and, in some instances, the specificity of LTR-retrotransposons elements, particularly Steamer elements in bivalves. Conclusions The diversity of immune molecules in M. mercenaria may allow this species to cope with varying and complex microbial and environmental landscapes. The repertoire of transposable elements identified in this study, particularly Steamer elements, should be a prime target for the investigation of cancer cell development and transmission among bivalve mollusks.

Aims: This research was aimed at assessing the nutritional properties and heavy metal compositions of African giant land snails (Archachatina marginata) and clams (Mercenaria mercenaria) from Ekowe community. Methodology: Mineral and vitamin contents were analyzed using the standard method of Association of Analytical Chemist. While standard wet digestion procedure was adopted in the sample preparation, heavy metals were analyzed using the Atomic Absorption Spectrophotometer technique. Results: Moisture contents were 76±0.63% & 78.4±0.06%, ash content, 1.37±0.01% & 3.45±0.01%, crude protein, 18.62±0.74% & 12.74±0.01% and lipid, 1.34±0.01% & 0.07±0.01% for Archachatina marginata and Mercenaria mercenaria respectively. Mineral contents were in this order: Ca > K > PO4> Mg > Na > Fe >Mn for Archachatina marginata while Mercenaria mercenaria was Ca> K > PO4 > Mg > Fe >Mn> Na. Vitamins profiles in Archachatina marginata were 5.20±0.198%, 0.144±0.004%, 0.05±0.003% and 0.78±0.035% for vitamin A, B1, B2 & E respectively. While Mercenaria mercenaria was 3.93±0.070%, 0.13±0.0025%, 0.075±0.001% & 0.84±0.01% for vitamins A, B1, B2 & E respectively. Heavy metal results in Archachatina marginata was in order of Zn > Cu > Cd > Ni > Cr while for Mercenaria mercenaria was Zn > Cu > Cd > Cr > Ni. Conclusion: These metal values were low and within the WHO permissible limits. The result shows that snail could complement the required micro and macro nutrients and vitamins needed for proper growth and development in human and hence recommended for regular consumption.

Ocean uptake of carbon dioxide (CO2) is causing changes in carbonate chemistry that affect calcification in marine organisms. In coastal areas, this CO2-enriched seawater mixes with waters affected by seasonal degradation of organic material loaded externally from watersheds or produced as a response to nutrient enrichment. As a result, coastal bivalves often experience strong seasonal changes in carbonate chemistry. In some cases, these changes may resemble those experienced by aquacultured bivalves during translocation activities. We mimicked these changes by exposing juvenile hard clams (500 μm, Mercenaria mercenaria) to pCO2 in laboratory upwellers at levels resembling those already reported for northeastern US estuaries (mean upweller pCO2 = 773, 1274, and 1838 μatm) and then transplanting to three grow-out sites along an expected nutrient gradient in Narragansett Bay, RI (154 bags of 100 clams). Prior to the field grow-out, clams exposed to elevated pCO2 exhibited larger shells but lower dry weight per unit volume (dw/V). However, percent increase in dw/V was highest for this group during the 27-day field grow-out, suggesting that individuals with low dw/V after the laboratory treatment accelerated accumulation of dw/V when they were transferred to the bay. Treatments also appeared to affect shell mineral structure and condition of digestive diverticula. Although treatment effects diminished during the field grow-out, clams that were pre-exposed for several weeks to high pCO2 would likely have been temporarily vulnerable to predation or other factors that interact with shell integrity. This would be expected to reduce population recovery from short-term exposures to high pCO2.

14 pages, 3 figures, 2 tables.-- This is Smithsonian Marine Station contribution #1138, In 2011, the Indian River Lagoon, a biodiverse estuary in eastern Florida (USA), experienced an intense microalgal bloom with disastrous ecological consequences. The bloom included a mix of microalgae with unresolved taxonomy and lasted for 7 months with a maximum concentration of 130 μg chlorophyll a L. In 2012, brown tide Aureoumbra lagunensis also bloomed in portions of this estuary, with reoccurrences in 2016 and 2018. To identify and understand the role of grazer pressure (top-down control) on bloom formation, we coupled DNA sequencing with bivalve feeding assays using three microalgae isolated from the 2011 bloom and maintained in culture. Feeding experiments were conducted on widely distributed bivalve species in the lagoon, including eastern oysters (Crassostrea virginica), hooked mussels (Ischadium recurvum), charru mussels (Mytella charruana), green mussels (Perna viridis), Atlantic rangia (Rangia cuneata), and hard clams (Mercenaria mercenaria), which were exposed to 3 × 10 cells mL of five species of microalgae consisting of A. lagunensis and the three species clarified herein, the picocyanobacteria Crocosphaera sp. and ‘Synechococcus’ sp., and the picochlorophyte Picochlorum sp., as well as Nannochloropsis oculata used as a control. To ensure clearance rates were indicative of consumption and assimilation, the microalgae were isotopically (N) labeled prior to feeding experiments. Clearance rates differed among bivalve and microalgal species, but enriched N values in bivalve tissue suggest that algal bloom species were assimilated by the bivalves. These results expand our understanding of the important ecosystem services that healthy, biodiverse filter feeder communities provide, We thank St. Johns River Water Management District (Contract 27799) and the Florida Fish and Wildlife Conservation Commission (FWC Agreement No. 13051) for funding the project, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

The interacting effects of little neck hard clam (Mercenaria mercenaria) density and bottom shear stress on cohesive sediment erodibility were investigated. Short-term stepwise erosion experiments in 30 and 40 cm diameter Gust microcosms over a range of 0.0083 to 0.1932 Pa were performed using sequential 20-minute constant shear stress steps while sampling turbidity regularly. In addition, sediment erodibility was monitored in two one-month long ecosystem experiments with tidal resuspension and 0, 10, and 50 hard clams in 1 m3 shear turbulence resuspension mesocosms (STURM) with an initial stepwise erosion experiment (0.313 to 0.444 Pa). In short-term erosion experiments, a low density of hard clams did not significantly affect sediment erodibility, but a high density of hard clams destabilized muddy sediments through significantly decreased critical shear stresses and higher erosion rates, resulting in higher cumulative suspended mass (CSM). In long-term erosion experiments, the sediment stabilized over time between treatments and decreased to a CSM of approximately 60 g m–2 with different densities of hard clams. This was likely due to development of microphytobenthos, mediated by the filter-feeding clams, bottom shear stress and increased light. Bioturbation by a dense bed of hard clams in interaction with infrequent high bottom shear due to storms may increase CSM in the water column, with subsequent direct and indirect effects on the ecosystem. However, more controlled longer-term erosion studies to determine the interacting effects of long-term exposure to high bottom shear stress, benthos, and microphytobenthos on sediment erodibility and benthic-pelagic coupling are needed.

In the present study, mechanochemical method has been used to synthesize Mercenaria shell powder as a cost-effective and eco-friendly photocatalyst. The catalyst powder was obtained by grinding method using Mercenaria shell, and it was characterized by various analytical techniques including UV-DRS, FTIR, XRD, SEM–EDAX, TGA and TEM analysis. The effect of various operational parameters such as concentration of dye, light intensity, amount of Mercenaria shell powder and effect of light has been studied on the rate of reaction. Mercenaria shell powder plays an important role in photocatalytic degradation of Eriochrome Black T dye. The recyclability of photocatalyst was also studied for the degradation of Eriochrome Black T dye, and the results obtained have been discussed. The degradation mechanism has been confirmed by using LC–MS analysis for Eriochrome Black T dye.

Circulating hemocytes in the hemolymph represent the backbone of innate immunity in bivalves. Hemocytes are also found in the extrapallial fluid (EPF), the space delimited between the shell and the mantle, which is the site of shell biomineralization. This study investigated the transcriptome, proteome, and function of EPF and hemolymph in the hard clam

In recent decades, the rate of introduction of non-indigenous macroalgae has increased. While invasive seaweeds often outcompete native species for substrata, their direct effects on marine life are rarely described. Here, we describe 'red water' events caused by the decay of blooms of the invasive red seaweed, Dasysiphonia japonica, in Great South Bay, NY, USA, and the ability of water from such events to induce rapid and significant mortality in larval and juvenile fish (Menidia beryllina, Menidia menidia, and Cyprinodon variegatus) and larval bivalves (Mercenaria mercenaria and Crassostrea virginica). All species studied experienced significant (p0.05) reductions in survival when exposed to macroalgae in a state of decay, seawater in which the alga was previously decayed, or both. Both bivalve species experienced 50-60% increases in mortality when exposed to decaying D. japonica for ∼ one week, despite normoxic conditions. Among fish, significant increases (40-80%) in mortality were observed after 24 h exposure to decayed D. japonica and one-week exposures caused, on average, 90% mortality in larval M. beryllina, 50% mortality in juvenile (∼3 cm) M. menidia, and 50% mortality in larval C. variegatus. All fish and bivalve mortality occurred under normoxic conditions (dissolved oxygen (DO)7 mg L

Ruditapes philippinarum and Mercenaria mercenaria are economically important bivalve species. The complete ribosomal DNA (rDNA) unit sequences of R. philippinarum and M. mercenaria, with as-sembled rDNA unit lengths of 12,910 and 12,100 bp, respectively, were obtained in this study for the first time. The rDNA unit structural organisation was similar to that in other eukaryotes, in-cluding the following elements in order: 18S rRNA-internal transcribed spacer 1 (ITS1), 5.8S rRNA-ITS2-28S rRNA-intergenic spacer (IGS) (3′ external transcribed spacer (ETS), non-transcribed spacer (NTS)-5′ ETS). The genetic differences between R. philippinarum and M. mercenaria were mainly attributable to non-coding regions (ITS1, ITS2 and IGS), especially the IGS region. The boundaries of putative 3′ ETS, NTS and 5′ ETS were confirmed. Seven and three sub-repeat fragments were found in R. philippinarum and M. mercenaria, respectively. These frag-ments ranged from 4 to 154 bp in length, and were located at the NTS and 5′ ETS regions. Five and six cytosine–guanine (CpG) islands were detected in R. philippinarum and M. mercenaria, respec-tively, and these covered 85.58% and 79.29% of the entire IGS sequence, respectively. The phylo-genetic tree was constructed based on Veneridae ITS and 18S rRNA sequences using the maxi-mum likelihood (ML) method. The ML tree based on ITS revealed that species within the same genus clearly clustered together with relatively high supporting values, and all the genera were recovered as monophyletic. The phylogenetic analyses using 18S rRNA provided a weaker phy-logenetic signal than ITS.

Oxygen fluctuations are common in marine waters, and hypoxia–reoxygenation (H–R) stress can negatively affect mitochondrial metabolism. The long-lived ocean quahog, Arctica islandica, is known for its hypoxia tolerance associated with metabolic rate depression, yet the mechanisms that sustain mitochondrial function during oxygen fluctuations are not well understood. We used top-down metabolic control analysis (MCA) to determine aerobic capacity and control over oxygen flux in the mitochondria of quahogs exposed to short-term hypoxia (24 h

Bivalves facilitate microbial nitrogen cycling, which can produce nitrous oxide (N2O), a potent greenhouse gas. Potential N2O production by three marine bivalves (Mytilus edulis, Mercenaria mercenaria and Crassostrea virginica) was measured in the laboratory including responses to nitrogen (N) loading and/or warming over short-terms (up to 14 or 28 days). N additions (targeting 100 μM-N ammonium nitrate) or warming (22 °C) individually and in combination were applied with experimental controls (20 μM-N, 19 °C). N2O production rates were higher with N additions for all species, but warming lacked significant direct effects. Ammonium and nitrate concentrations varied but were consistent with nitrification as a potential N2O source for all bivalves. Highest N2O emissions (7.5 nmol N2O g−1 h−1) were from M. edulis under hypoxic conditions coincident with a drop in pH. Macro-epifauna on M. edulis did not significantly alter N2O production. Thus, under short-term hypoxic conditions, micro-organisms in M. edulis guts may be a particularly significant source of N2O.

Synthesis of strontium-doped hydroxyapatite from Mercenaria clam shells has been carried out by hydrothermal method. The doping of bioceramic, processed from biogenic resources is mostly unexplored. The objective is to understand the effect of strontium (Sr) incorporation on phase stability, sintering behaviour, mechanical properties and cytotoxicity of hydroxyapatite (HAp) derived from clam shells. The different molar concentrations of Sr, varies from 10, 30, 50, 70% of Ca, were substituted into the HAp. The synthesized powders were sintered at 1200 °C in air. The as synthesized powders and sintered specimens were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and high resolution transmission electron microscopy. The crystallite size and cell parameters of sintered specimens were analyzed from XRD. The XRD of hydrothermally synthesized powders mostly matched with HAp with slight shifting due to Sr doping. However, some distinct Sr based compounds were also observed where Sr substitution is more that 50% of Ca. The XRD of sintered specimen showed increasing β-tricalcium phosphate (β-TCP) phase with Sr substitution. The sintered density of solid samples gradually increased from 3.04 g/cc to 3.50 g/cc and surface energy decreased with increasing Sr substitution. Similarly, microhardness, fracture toughness and nanohardness of solid samples found to be enhanced with Sr substitution. The elastic modulus gradually increased from 130 to 137 GPa for HAp and Sr substituted HAp (70% of Ca). The in vitro cytotoxicity of sintered specimen against mouse osteoblast cell line showed that all the samples were nontoxic. However cell proliferation found low for the solid samples containing more than 50% Sr substitution.

Biological activity of tissues and enzyme hydrolyzates is investigated for three species of bivalve mollusks:Corbicula japonica,Mercenaria mercenaria, andAnadara broughtonii. Antiradical activity of all samples has increased signifcantly during their enzymatic hydrolysis: in eight times forC. japonica, in three times forM. mercenaria, and in 2.5 times forA. broughtonii. The highest anti-trombolitic activity (0.0823 units) is found for the hydrolyzate ofC. japonicain concentration of 10 mg/mL. Angiotensin I-converting enzyme inhibitory activity is found only for the hydrolyzate ofM. mercenariain concentration of 10–100 mg/mL. The maximum inhibitory activity for alpha-amylase and alpha-glycosidase (7.5 and 7.2 %, respectively) is observed for the hydrolyzate ofM. mercenariain concentration 1 mg/mL. Hepatoprotective activity, measured by survival rate of HepG2 hepatocytes, is detected for the hydrolyzate of tissues for all species in weak concentrations: 0.1 mg/mL forC. japonicaandM. mercenariaand 0.2 mg/mL forA. broughtonii.

Touristic and commercial shipping traffic, the import of fish products and aquaculture activities are the most important vectors for the introduction of non-indigenous species (NIS) in the Mediterranean Sea. In this context, the Venice Lagoon (North Adriatic Sea) is considered a hotspot of NIS introductions. Among macroalgae, identification of these alien taxa on the basis of morphological characters is difficult due to their simple morphology, phenotypic plasticity and the occurrence of morphologically overlapping species. Here we report three new introduced species for the Mediterranean Sea: Aglaothamnion halliae, Melanothamnus japonicus and Polysiphonia schneideri. The samples belong to different genera of the order Ceramiales (Rhodophyta) and were collected in six stations of the Venice Lagoon. Aglaothamnion halliae and Melanothamnus japonicus were probably introduced via shellfish products, in particular, with the American clam, Mercenaria mercenaria, and with the Japanese oyster, Magallana gigas, respectively. Polysiphonia schneideri, instead, appears to have been introduced from Spain via the Strait of Gibraltar as a fouling organism on ship hulls. The presence of closely related cryptic species in the Venice Lagoon, such as Aglaothamnion tenuissimum, Melanothamnus harveyi and Polysiphonia denudata, and the lack of diagnostic characters can lead to the underestimation of the biodiversity of these genera. For these reasons, we used DNA barcoding to discover and correctly identify these new introduced specimens.

Life span bias potentially alters species abundance in death assemblages through the overrepresentation of short-lived organisms compared with their long-lived counterparts. Although previous work found that life span bias did not contribute significantly to live–dead discordance in bivalve assemblages, life span bias better explained discordance in two groups: longer-lived bivalve species and species with known life spans. More studies using local, rather than global, species-wide life spans and mortality rates would help to determine the prevalence of life span bias, especially for long-lived species with known life spans. Here, we conducted a field study at two sites in North Carolina to assess potential life span bias between Mercenaria mercenaria and Chione elevata, two long-lived bivalve species that can be aged directly. We compared the ability of directly measured local life spans with that of regional and global life spans to predict live–dead discordance between these two species. The shorter-lived species (C. elevata) was overrepresented in the death assemblage compared with its live abundance, and local life span data largely predicted the amount of live–dead discordance; local life spans predicted 43% to 88% of discordance. Furthermore, the global maximum life span for M. mercenaria resulted in substantial overpredictions of discordance (1.4 to 1.6 times the observed live–dead discordance). The results of this study suggest that life span bias should be considered as a factor affecting proportional abundances of species in death assemblages and that using life span estimates appropriate to the study locality improves predictions of discordance based on life span compared with using global life span estimates.

Increased consumption and improper disposal of prescription medication, such as beta (β)-blockers, contribute to their introduction into waterways and may pose threats to non-target aquatic organisms. There has been rising concern about the impacts of these prescription drugs on coastal ecosystems, especially because wastewater treatment plants are not designed to eliminate them from the discharge. Few studies have characterized the sublethal effects of β-blocker exposures in marine invertebrates. The overall aim of our research is to identify cellular responses of two commercially important filter-feeding marine bivalves, hard clams (Mercenaria mercenaria) and Eastern oysters (Crassostrea virginica), upon exposures to two β-blocker drugs, propranolol and metoprolol. In vitro exposures with bivalve digestive gland and gill tissues were conducted where tissues were separately exposed to each drug for 24 h. Tissue samples were analyzed for cellular damage (lysosomal membrane destabilization and lipid peroxidation), total antioxidant capacity, and glutathione-s-transferase activity. Elevated damage and changes in enzyme activities were noted in the exposed tissues at environmentally relevant concentrations. Differences in species and tissue sensitivities and responses to exposures were also observed. These studies enhance our understanding of the potential impacts of prescription medication on coastal organisms. Additionally, this work demonstrates that filter-feeders may serve as good model organisms to examine the effects of unintended environmental exposures to β-blockers. These studies are part of our ongoing work aimed at evaluation of sublethal biomarkers of pharmaceutical exposures and identification of key events that can contribute to the development of adverse outcome pathways (AOPs).

QPX (Quahog Parasite Unknown), a thraustochytrid, is the source of morbidity and mortality in hard clams, Mercenaria mercenaria along the northeast coast of North America. The QPX organism is a facultative pathogen that results in disease in clams held at high densities and salinities. The disease most commonly causes losses in two-year-old aquacultured clams. In some locations, nodules and swellings containing QPX can be identified in the mantle often in areas adjacent to the siphon. Histologically, the organism is surrounded by thick mucus that inhibits phagocytosis by the clam's inflammatory cells especially during the spring and fall when the clam's immune system is less active. Variability in severity of infection and morbidity has been associated with origin of the brood stock with juvenile clams from southern U.S. brood stock being the most affected.

Background Inhibitors of apoptosis (IAPs) are critical regulators of programmed cell death that are essential for development, oncogenesis, and immune and stress responses. However, available knowledge regarding IAP is largely biased toward humans and model species, while the distribution, function, and evolutionary novelties of this gene family remain poorly understood in many taxa, including Mollusca, the second most speciose phylum of Metazoa. Results Here, we present a chromosome-level genome assembly of an economically significant bivalve, the hard clam Mercenaria mercenaria, which reveals an unexpected and dramatic expansion of the IAP gene family to 159 members, the largest IAP gene repertoire observed in any metazoan. Comparative genome analysis reveals that this massive expansion is characteristic of bivalves more generally. Reconstruction of the evolutionary history of molluscan IAP genes indicates that most originated in early metazoans and greatly expanded in Bivalvia through both lineage-specific tandem duplication and retroposition, with 37.1% of hard clam IAPs located on a single chromosome. The expanded IAPs have been subjected to frequent domain shuffling, which has in turn shaped their architectural diversity. Further, we observed that extant IAPs exhibit dynamic and orchestrated expression patterns among tissues and in response to different environmental stressors. Conclusions Our results suggest that sophisticated regulation of apoptosis enabled by the massive expansion and diversification of IAPs has been crucial for the evolutionary success of hard clam and other molluscan lineages, allowing them to cope with local environmental stresses. This study broadens our understanding of IAP proteins and expression diversity and provides novel resources for studying molluscan biology and IAP function and evolution.

The goal of this study was to evaluate the efficacy of phenotypic traits and two genetic assays to distinguish between Mercenaria mercenaria, an important aquaculture species, and Mercenaria campechiensis, a conspecific species that is partially sympatric, but that has not been successfully farmed. The objectives were to evaluate (1) four established diagnostic phenotypic traits (lunule shape, thickness of concentric shell ridges, prominence of anterior side of the concentric ridges, and presence of purple nacre inside of the shells) to distinguish between species, (2) size polymorphism of PCR fragments from four genes [16S rRNA, 18S rRNA, Internal Transcribed Spacer genes (ITS1 and ITS2)], and (3) PCR-restriction fragment length polymorphism (RFLP) on three of these genes (16S, ITS1, and ITS2). Phenotypic traits correctly distinguished two geographically distant conspecific populations (two locations in Maine for M. mercenaria and in Bradenton, FL, for M. campechiensis); however, among all other locations, both species had overlapping phenotypic trait values. Although PCR fragments were obtained for all genes tested, size polymorphism was not identified between the two species. Restriction enzyme digestion of PCR fragments resulted in diagnostic fragments distinguishing the two species for 16S, ITS1, and ITS2. Although phenotypic scores failed to delineate between the two species in most locations, PCR-RFLP results failed to identify hybrids in wild or hatchery samples. Further investigation is needed to apply the PCR-RFLP assays on known hybrid offspring from crosses of M. mercenaria and M. campechiensis. Results have elucidated the difficulties in confidently detecting hybridization in quahogs; however, determining effective methods for species identification and hybrid detection will be important to address issues such as the prevalence and distribution of hybridization in aquaculture and in wild populations, and to determin the presence of M. campechiensis which are currently difficult to find.