Hemolymph acid phosphatase activity pattern in copper-stressed bivalves

Gene cloning and transcriptional regulation of the alkaline and acid phosphatase genes in Scylla paramamosain

In crustaceans, innate immunity serves as the frontline of defense against microbes. Alkaline phosphatases (ALPs) and acid phosphatases (ACPs) are essential enzymes that play a significant role in crustaceans' immune defenses. However, the function and transcriptional regulation of the alp and acp genes in the Scylla paramamosain, an important aquaculture species in China, have not been elucidated. In this study, the full-length cDNAs of Spalp and Spacp were identified, which consist of 2,718 bp and 3,768 bp, encoding 579 and 452 amino acids, respectively. Multiple sequence alignment and phylogenetic analysis showed that these two genes were conserved among different species and shared high homology with crustaceans. The mRNA expression of Spalp and Spacp were examined in eight tested tissues, with the highest levels in the hepatopancreas. The 5'-flanking regions of Spalp and Spacp were cloned and sequenced. The core promoter region of the Spalp and Spacp was -39 bp∼+8 bp and -39 bp∼+10 bp, respectively. Potential binding sequences for SOX-2, c-fos, SP1, NF-κB, GATA-1, YY1, and AP-1 transcription factors were found in the 5'-flanking regions of Spalp and Spacp. The NF-κB binding site located between -1,223 bp and -972 bp in Spalp while SP1 and AP-1 binding sites located between -1,249 bp and -514 bp in Spacp. Mutation analysis confirmed that NF-κB negatively regulated the expression of Spalp gene, and SP1 and AP-1 positively regulated Spacp gene expression. These results provide us with essential information to elucidate the function of the Spalp and Spacp in S. paramamosain. This study is the first one to analyze the activity of Spalp and Spacp promoters.

Comparison of viability and phagocytic responses of hemocytes withdrawn from the bivalves Mytilus edulis and Dreissena polymorpha, and exposed to human parasitic protozoa

Bivalve molluscs are now considered indicator species of aquatic contamination by human parasitic protozoa. Nonetheless, the possible effects of these protozoa on the immune system of their paratenic hosts are poorly documented. The aim of this study was to evaluate the effects of two protozoa on hemocyte viability and phagocytosis from two mussels, the zebra mussel (freshwater habitat) and the blue mussel (seawater habitat). For these purposes, viability and phagocytic markers have been analysed on hemocytes from mussels without biological stress (control hemocytes), and on hemocytes exposed to a biological stress (Toxoplasma gondii and Cryptosporidium parvum oocysts). We report, for the first known time, the interactions between protozoa and hemocytes of mussels from different aquatic environments. Zebra mussel hemocytes showed a decrease in phagocytosis of fluorescent microbeads after exposure to both protozoa, while blue mussel hemocytes reacted only to T. gondii oocysts. These decreases in the ingestion of microbeads can be caused by competition between beads and oocysts and can be influenced by the size of the oocysts. New characterisations of their immune capacities, including aggregation, remain to be developed to understand the specificities of both mussels.

Effects of Marine Toxin Domoic Acid on Innate Immune Responses in Bay Scallop Argopecten irradians

Domoic acid (DA) is an amnesic shellfish poisoning toxin produced by some species of the genera Pseudo-nitzschia and Nitzschia. This toxin has harmful effects on various species, especially scallops. This study aimed to investigate the effects of DA exposure on the immune and physical responses of bay scallop, Argopecten irradians. Various immunological and physical parameters were assessed (acid phosphatase (ACP), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), lipid peroxide (LPO), nitric oxide (NO), and the total protein content) in the haemolymph of scallops at 3, 6, 12, 24, and 48 h post-exposure to DA at different concentrations (10, 50, and 100 ng/mL). Moreover, the expression of immune-related genes (CLT-6, FREP, HSP90, MT, PGRP, and PrxV) was assessed. The activities of ACP, ALP, and LDH and the total protein content and LPO increased upon exposure to DA at different concentrations, while NO levels were decreased. Furthermore, immune-related genes were assessed upon DA exposure. Our results showed that exposure to DA negatively impacts immune function and disrupts physiological activities in bay scallops.

Effect of the Algicide Thiazolidinedione 49 on Immune Responses of Bay Scallop Argopecten Irradians

The thiazolidinedione 49 (TD₄₉) is an effective algaecide against harmful algae; however, its potential effects on the immune function of the edible bay scallop are unclear. Therefore, the present work studied the effects of TD₄₉ on the immune response in bay scallop by evaluating activities of acid phosphatase (ACP), alkaline phosphatase (ALP), and superoxide dismutase (SOD), as well as nitric oxide (NO) levels, total protein content, and expression of immune genes (CTL-6, PGRP, PrxV, MT, and Cu/Zn-SOD) at 3–48 h post-exposure (hpe) to TD₄₉. The activities of ACP and ALP significantly increased in TD₄₉-treated groups at 3–24 hpe, whereas NO levels decreased significantly in 0.58 and 0.68 μM of TD₄₉ at 6–24 hpe, after which the level was similar to that in the untreated control. Moreover, SOD activity significantly increased in all three concentration groups at 3–6 hpe, while it decreased at 12 hpe in the 0.68 μM TD₄₉ treatment group. Notably, total protein content increased with TD₄₉ treatment at each time interval. The results revealed that variable effects on the expression of immune-related genes were observed after treatment with TD₄₉. The findings demonstrate that exposure of scallops to TD₄₉ changes immune responses and expression of immune-related genes. We hypothesize that TD₄₉ may disrupt immune system in bay scallop. The current investigation highlights the potential negative effects of using TD₄₉ as an algaecide on marine economic bivalves to control harmful algal blooms in marine environments.

Detoxification, Apoptosis, and Immune Transcriptomic Responses of the Gill Tissue of Bay Scallop Following Exposure to the Algicide Thiazolidinedione 49

Thiazolidinedione 49 (TD₄₉), a newly synthesized algicide, shows strong toxicity at low concentrations of 0.1-2.0 μM. However, its potential effects on non-target species at the transcript level were not investigated. Differentially expressed genes (DEGs) in the gills of the bay scallop, Argopecten irradians, were accessed after treatment with 0.68 μM TD₄₉ for up to 48 h. Following exposure, it was observed that 5214 genes were upregulated and 3497 were downregulated. Functional enrichment analysis revealed that the apoptosis pathway was activated. The extrinsic apoptosis pathway was activated and the survival factors related pathway was suppressed. Furthermore, gene expressions related to ATP-binding cassette, nuclear factor erythroid 2-related factor, B cell lymphoma-2 family protein, glutathione reductase, glutathione peroxidase, catalase, NADPH2:quinone reductase, and superoxide dismutase were decreased. Conversely, gene expressions related to FAS-associated death domain protein, glutathione S-transferase, caspase 6, 8, cytochrome P450 1A1, and 2C8 were increased. These results comprehensively demonstrated the toxicity of the novel algicide TD₄₉, and should draw the attention of researchers to the importance of analyzing the potential impact of chemical compounds as algicides to control the proliferation of harmful algae, due to the secondary pollution caused by their application.

Ecotoxicological biomarkers as investigating tools to evaluate the impact of acrylamide on Theba pisana snails

Acrylamide (ACR) is a widespread industrial chemical with recognized adverse effects not only to humans but to other organisms in the environment as well. In the present study, the ecotoxicological effects of dietary exposure to sublethal concentration (1/20 LC₅₀) of ACR on the land snail, Theba pisana after 2 weeks of exposure and 1-week recovery with respect to oxidative stress parameters; lipid peroxidation (LPO), reduced glutathione (GSH), catalase (CAT), and glutathione-S-transferase (GST), cytogenetic parameter; deoxyribonucleic acid (DNA) content, as well as immunological parameters; cell death, phagocytosis, lysosomal membrane stability (LMS), lectins, superoxide anion (O₂^-) generation, phenoloxidase (PO), peroxidase (POD), and hemocyanin (Hc) were examined. The results showed that ACR significantly increased LPO level and the activity of CAT and GST, cell death, and Hc level, whereas a significant decline in DNA and GSH contents, phagocytic activity, LMS, lectins, O₂^- generation, POD, and PO activities compared to the controls after 2-week exposure was observed. After 1-week recovery, most of the tested parameters in exposed snails were permanent and not reversible to the control levels. This study suggests that the tested multiple parameters of T. pisana species may be used as biomarkers of ACR exposure. Besides, T. pisana snails could be used as a good sentinel organism for ACR exposure in pollution monitoring studies.

Impact of multiple stressors on biomarker responses in sympatric dreissenid populations

Dreissenid mussels, well-known invaders of the northern hemisphere, also constitute good biomonitors for freshwater quality assessment. Whereas the oldest, Dreissena polymorpha, is relatively well-known, the new invasive, Dreissena rostriformis bugensis, has been very little characterized. The aim of this study was to compare subcellular biomarker responses within these species, by taking into account inter- and intra-specific variability in biomarker responses during a multi-stress assessment. Indeed, due to local environmental conditions and genetic background, biomarker responses can be different between populations of a given species, not only between species. To evaluate these differential responses, we sampled mussels on two sites where they are both present in sympatry (plus another D. r. bugensis population), and we exposed these populations in laboratory to different stressors: thermal stress (12 or 17 °C), dietary stress (fed or unfed), contamination (nickel at 0, 20 and 500 μg L^-1) and exposure duration (0, 4 or 8 days). Results mainly evidenced strong inter-species and inter-population differences, underlining the need to discriminate correctly between the two species and to know well the populations used in biomonitoring. Results also evidenced thermal and food stress-related effects. The numerous data obtained during this multi-stress experiment also highlight the complexity of working on several stressors and analysing the associated results.

The influence of salinity on the fate and behavior of silver standardized nanomaterial and toxicity effects in the estuarine bivalve Scrobicularia plana

Because of their antibacterial properties, silver (Ag) engineered nanomaterials are included in many products. The present study used a standardized Ag nanomaterial (NM-300K, 20 nm) supplied with a stabilizing agent. The aim was to investigate the behavior of Ag nanomaterial in an estuarine-like medium at 2 salinities (15 psu and 30 psu). Uptake as well as sublethal effects of Ag nanomaterial (10 μg Ag/L), its stabilizing agent, and AgNO₃ (10 μg Ag/L) were assessed in the clam Scrobicularia plana, after 7 d of exposure. The release of soluble Ag from Ag nanomaterial in the experimental media was quantified by using diffusive gradient in thin films and ultrafiltration. A multibiomarker approach was employed to reveal responses of clams at subindividual and individual levels. The bioaccumulation of Ag was significantly greater at 15 psu versus 30 psu, which could be explained by differences in Ag speciation. In conclusion, the present study showed different impacts of Ag nanomaterial that were not always explained by the release of Ag ions in clams at both salinities; such impacts were particularly characterized by induction of oxidative stress, cell damage, and impairment of energetic levels. Burrowing of clams was affected by the stabilizing agent depending on the salinity tested, with stronger effects at 15 psu. Finally, the present study highlighted salinity-dependent changes in the physiology of estuarine bivalves. Environ Toxicol Chem 2016;35:2550-2561. © 2016 SETAC.

Morphological alteration, lysosomal membrane fragility and apoptosis of the cells of Indian freshwater sponge exposed to washing soda (sodium carbonate)

Washing soda is chemically known as sodium carbonate and is a component of laundry detergent. Domestic effluent, drain water and various anthropogenic activities have been identified as major routes of sodium carbonate contamination of the freshwater ecosystem. The freshwater sponge, Eunapius carteri, bears ecological and evolutionary significance and is considered as a bioresource in aquatic ecosystems. The present study involves estimation of morphological damage, lysosomal membrane integrity, activity of phosphatases and apoptosis in the cells of E. carteri under the environmentally realistic concentrations of washing soda. Exposure to washing soda resulted in severe morphological alterations and damages in cells of E. carteri. Fragility and destabilization of lysosomal membranes of E. carteri under the sublethal exposure was indicative to toxin induced physiological stress in sponge. Prolonged exposure to sodium carbonate resulted a reduction in the activity of acid and alkaline phosphatases in the cells of E. carteri. Experimental concentration of 8 mg/l of washing soda for 192 h yielded an increase in the physiological level of cellular apoptosis among the semigranulocytes and granulocytes of E. carteri, which was suggestive to possible shift in apoptosis mediated immunoprotection. The results were indicative of an undesirable shift in the immune status of sponge. Contamination of the freshwater aquifers by washing soda thus poses an alarming ecotoxicological threat to sponges.

Enzymatic biomarkers as indicators of dietary cadmium in gypsy moth caterpillars

Heavy metals damage the structure, chemistry, and function of cells, including enzyme systems inside them. Variation in the profile of biochemical biomarkers in prevalent species should be used for assessing environmental contamination. The present study pays attention to the phosphatases present in the midgut of gypsy moth fourth instar caterpillars, which had been exposed to short- and long-term cadmium intake at 10 and 30 μg Cd/g dry food. Chronic cadmium ingestion significantly inhibited the activity of all examined phosphatases, while only the activity of lysosomal phosphatase was acutely decreased. Total acid phosphatase activity recovered from both long-term cadmium treatments within 3 days. The low index of phenotypic plasticity was connected to high variability of plasticity. Dependence of phosphatase isoforms on genotype and duration of cadmium treatment was determined. We concluded that, with further investigations, profiling of total acid phosphatase activity, as well as the lysosomal fraction can be used as a biomarker for acute sublethal metal toxicity.

Oxidative stress and immunologic responses following a dietary exposure to PAHs in Mya arenaria

Background

The aim of this research was to investigate oxidative stress and immune responses following a dietary polycyclic aromatic hydrocarbon (PAH) exposure in a marine bioindicator organism, the soft shell clam, Mya arenaria. Immune parameters in hemolymph (haemocyte number, efficiency of phagocytosis and haemocyte activity) and assessment of oxidative stress using catalase (CAT) activity and levels of malondialdehyde (MDA) performed on the digestive gland were estimated as biomarkers in clams fed in mesocosm with PAH contaminated phytoplankton. MDA levels and CAT activities were also measured in situ in organisms sampled in a control site (Metis Beach, Québec, Canada) as well as organisms sampled in a site receiving domestic effluents (Pointe-au-Père, Québec, Canada), to assess effects of abiotic variables related to seasonal variations and mixed contamination on the selected parameters.

Results

Results on immune parameters suggest that the PAHs may interfere with the maturation and/or differentiation processes of haemocytes. MDA results showed that lipid peroxidation did not occur following the exposure. The levels of CAT activity corresponded to weak antioxidant activity (no significant differences). Recovery was noted for all the immune endpoints at the end of the experiment.

Conclusion

Results suggest that immune parameters are early biomarkers that can efficiently detect a physiological change during a short term exposure to low concentrations of PAHs. The in situ survey (in the natural environment) suggested that clams from the Pointe-au-Père site did not show any oxidative stress as well as the clams contaminated in mesocosm, probably due to the low concentrations of PAHs used for this study. MDA levels increased however in organisms from Metis Beach, a response probably related to domestic effluents or parasitism.

Mechanical disturbance affects haemocyte functionality in the Venus clam Chamelea gallina

The clam Chamelea gallina is fairly common along the western coastline of the Adriatic Sea, where it is subjected to intense fishing. To evaluate possible causes of stress in clam populations, the effects of acute mechanical disturbance on haemocyte functionality were analysed in both laboratory and field experiments. Among the various sources of stress that clams undergo during commercial fishing by hydraulic dredges, water pressure and mechanical sorting were considered, and three increasing levels of stress were applied. A reduction in immunosurveillance was highlighted, concentrations of circulating haemocytes, phagocytic and acid phosphatase activity indices decreased with increasing mechanical stress. The opposite trend shown by the beta-glucuronidase activity index is discussed. The response of clam haemocytes, detected on seasonal bases in two sites, often exhibited peculiar patterns, mostly depending on the reproductive cycle, and were probably influenced by different features of the sea bottom. Although recovery after stress was observed in laboratory experiments, some considerations are made on detrimental effects experienced in the field by under-sized clams, which are first fished and then thrown back into the sea.

Comparisons of PAH-induced immunomodulation in three bivalve molluscs

There is growing evidence that contaminants may be partly responsible for the observed increase in disease in marine organisms by adversely affecting their immunity. Bivalve molluscs are common sentinels used in invertebrate immunotoxicology, however, to date, studies have been restricted to a few resilient species. This present study is a comparative investigation into the effects of the polycyclic aromatic hydrocarbon, phenanthrene, on the immunocompetence of three bivalve species. The commonly-studied marine mussel, Mytilus edulis, was compared with two species that have never been studied with respect to immunomodulation, namely, the edible cockle, Cerastoderma edule and the razor shell, Ensis siliqua. Animals were exposed to a range of phenanthrene concentrations (50, 100, 200 or 400 microg l(-1)) and haemocyte immune parameters, including haemocyte counts, phagocytosis, superoxide generation, lysosomal enzymes and lectin-binding, were monitored. Aims were not only to extend existing knowledge of bivalve immunotoxicology, but also to establish whether contaminant-induced immunomodulation in the sentinel species, M. edulis, is comparable to that observed in other bivalves. Results showed that the immune response of the three species was differentially affected by phenanthrene exposure, with immunomodulation in M. edulis not reflecting the immunological changes observed in the other two species. This suggests M. edulis may not be a suitable sentinel bivalve, and that other species, such as C. edule, may more accurately reflect the general immunological response of this group of marine animals.

Structural and functional characterisation of the blood cells of the bivalve mollusc, Scrobicularia plana

Light and electron microscopical studies were carried out in order to characterise the blood cells of the bivalve mollusc, Scrobicularia plana. Three types of haemocytes were recognised: eosinophilic granular haemocytes, basophilic granular haemocytes and basophilic agranular haemocytes. The eosinophilic granulocytes were vesicular and contained large granules whereas the basophilic granulocytes were found to contain small granules and glycogen 'lakes'. The basophilic agranular haemocytes were significantly smaller than the granular haemocytes and had a high nucleus to cytoplasm ratio. Functional characterisation of the blood cells identified activity for the lysosomal enzymes: acid phosphatase, beta-glucuronidase, non-specific esterase and arylsulphatase. There was also a weak staining reaction for phenoloxidase and peroxidase activities. Phagocytosis of Gram-positive bacteria was demonstrated by the haemocytes and antibacterial activity was shown by cell-free haemolymph. Assays to determine release of reactive oxygen species from the haemocytes did not detect any reactive oxygen generation.

Air exposure and functionality of Chamelea gallina haemocytes: effects on haematocrit, adhesion, phagocytosis and enzyme contents

The Venus clam Chamelea gallina is fairly common along the western coasts of the Adriatic and is subjected to intense fishing. Since over the last 20 years extensive hypoxic and anoxic conditions have repeatedly damaged this natural resource, we decided to study the effects of anoxic stress on the functionality of clam haemocytes and the consequences on immune responses. Clams, exposed to air, close their valves and tissues become anoxic and metabolism processes switch to anaerobiosis. In these conditions, a significant decrease in the haematocrit value and in the percentage of acid phosphatase-positive haemocytes was observed, while the number of cells with beta-glucuronidase significantly increased after day 1. The above indices generally returned to control values when clams were re-immersed in seawater after 1 day of treatment. Clams exposed to air for 2 days and then re-immersed, attempted to recover in the subsequent 3 days. Animals had fully recovered on day 4. Three-day-exposed clams did not recover. Phagocytic and adhesion indices decreased significantly after the first day of air exposure. The change in frequency of three types of circulating cells (spreading, round, apoptotic) was also monitored.