Exposure to 2,3,7,8-tetrachlorodibenzo-paradioxin (TCDD) hampers the host defense capability of a bivalve species, Tegillarca granosa.

Though increasing reports of deleterious impacts of dioxins and polychlorinated biphenyls (PCBs) on a variety of marine organisms have been described, their effects on the host defense capability of marine bivalve mollusks remain poorly understood. In the present study we used 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as a representative of dioxins and PCBs to investigate its impacts on the host defense capability of the blood clam, Tegillarca granosa. After exposure of clams to a range (0, 0.01, 0.1, 1, and 10 µg/L) of TCDD for 96 h, the total count, cell type composition, and phagocytic rate of haemocytes were analyzed. In addition, alkaline phosphatase (ALP) activity, cell viability, and the extent of DNA damage of haemocytes were also investigated. Our results showed that exposure to relatively high TCDD concentrations led to significant reductions in the total count and phagocytic activity of haemocytes, which could be accounted by aggravated DNA damage and reduced cell viability. In addition, the percentage of red granulocyte was significantly decreased whereas that of basophil granulocyte was significantly increased upon high doses TCDD exposure (effective concentrations are 1 µg/L and 10 µg/L for red and basophil granulocytes, respectively). Moreover, clams exposed to TCDD had a significant higher activity of ALP, may also indicate an enhanced ability to eliminate pathogens through direct dephosphorylation process whereas a suppressed inflammatory response through indirect regulating of downstream molecular cascade reaction. These findings suggest that TCDD may hamper the host defense capability and therefore render bivalve mollusks more vulnerable to pathogen infections.

Exposure to Waterborne nTiO2 Reduces Fertilization Success and Increases Polyspermy in a Bivalve Mollusc: A Threat to Population Recruitment.

Fertilization success is crucial for the population recruitment of an organism. However, little is known about the threat of nanoparticles (NPs) to the fertilization of broadcast spawners. Therefore, the effects of nTiO2 on fertilization success, polyspermy rate, sperm velocity, gametic DNA damage, sperm-egg collision probability, gamete fusion, and oocyte ultrastructure were investigated in a broadcast spawning bivalve, Tegillarca granosa. The results obtained show that fertilization success significantly decreased, whereas polyspermy risk markedly increased upon nTiO2 exposure. In addition, nTiO2 exposure led to a significant reduction in sperm swimming velocity, which would subsequently constrain gamete collisions. In addition, nTiO2 exposure resulted in a significant decline in gamete fusion per collision along with aggravated DNA damage in gametes. Furthermore, ultrastructural analysis illustrated the attachment of nTiO2 to the oocyte surface, which subsequently resulted in microvillus disassociation and plasma membrane damage. In conclusion, the results obtained suggest a significant threat from NP pollution to the recruitment of broadcast spawning invertebrates.

Waterborne Cd2+ weakens the immune responses of blood clam through impacting Ca2+ signaling and Ca2+ related apoptosis pathways.

Exposure to heavy metals such as Cadmium (Cd) may exert detrimental impacts on the immune responses of marine bivalve species. However, the immunotoxicity of Cd on blood clams remains unknown to date. Furthermore, though Cd2+ is known to compete with calcium (Ca2+) ions for their binding sites in cells and inhibit Ca2+ influx, whether Cd2+ weakens the immune responses of marine bivalves through inducing intracellular Ca2+ disorders still remains unclear. Therefore, the immunotoxicity of Cd2+ at different waterborne Ca2+ concentrations on blood clam, Tegillarca granosa, were investigated in the present study. Results obtained demonstrated that the total number, phagocytic activity, and red granulocytes ratio of the haemocytes were all significantly reduced after 10 days exposure of individuals to 25 µg/L Cd2+. However, when the waterborne Ca2+ concentrations were elevated by 10% and 20% (approximately 370 and 410 mg/L, respectively), mitigation effects on the immune responses of individuals were detected. In addition, though the expressions of genes from the Ca2+ signaling and Ca2+-related apoptosis pathways were significantly altered by Cd2+ exposure, the expression patterns of these genes were similar to that of the control when the waterborne Ca2+ concentrations were elevated, suggesting a relieving effect of waterborne Ca2+ on Cd2+ induced toxicity to haemocytes. The results obtained in the present study revealed that waterborne Cd2+ may hamper the immune responses of T. granosa through influencing Ca2+ signaling and Ca2+-related apoptosis pathways, which can be partially mitigated by elevating the waterborne Ca2+ concentrations.

The synergic impacts of TiO2 nanoparticles and 17ß-estradiol (E2) on the immune responses, E2 accumulation, and expression of immune-related genes of the blood clam, Tegillarca granosa.

The extensive use of TiO2 nanoparticles (nTiO2) in industrial products has led to their release into the marine environment, thereby posing a potential risk to marine organisms. However, in addition to affecting marine organisms through its inherent properties, nTiO2 can also act as a vehicle for other toxic pollutants due to their strong adsorption ability through the "Trojan horse" effect. Due to their potential hazard, the endocrine disrupting chemicals (EDCs) such as 17ß-estradiol (E2), have been considered as one of the most serious anthropogenic threats to biodiversity and ecosystem health. However, there is still a lack of knowledge regarding the possible synergistic effects of nTiO2 and endocrine disrupting chemicals (EDCs) on marine organisms to date. Therefore, the combined effects of nTiO2 and 17ß-estradiol (E2) on the immune responses of the blood clam, Tegillarca granosa, were investigated in this study. After 10 days of treatment, the total number, phagocytic activity, red granulocytes ratio, and the phagocytosis of hemocytes were significantly reduced in almost all treatment groups. Furthermore, expressions of genes from NFκß and Toll-like receptor signaling pathways were significantly altered after exposure to nTiO2 and/or E2, indicating a reduced sensitivity to pathogen challenges. In addition, compared to exposure to E2 alone, co-exposure to E2 and nTiO2 led to a significant increase in the content of alkali-labile phosphate (ALP) in hemolymph, suggesting an enhanced E2 bioconcentration in the presence of nTiO2. In general, the present study demonstrated that nTiO2 enhanced the immunotoxicity of E2 to the blood clam, which may be due to the increased E2 uptake in the presence of nTiO2.

Enhanced bio-decolorization of 1-amino-4-bromoanthraquinone-2-sulfonic acid by Sphingomonas xenophaga with nutrient amendment.

Bacterial decolorization of anthraquinone dye intermediates is a slow process under aerobic conditions. To speed up the process, in the present study, effects of various nutrients on 1-amino-4-bromoanthraquinone-2-sulfonic acid (ABAS) decolorization by Sphingomonas xenophaga QYY were investigated. The results showed that peptone, yeast extract and casamino acid amendments promoted ABAS bio-decolorization. In particular, the addition of peptone and casamino acids could improve the decolorization activity of strain QYY. Further experiments showed that l-proline had a more significant accelerating effect on ABAS decolorization compared with other amino acids. l-Proline not only supported cell growth, but also significantly increased the decolorization activity of strain QYY. Membrane proteins of strain QYY exhibited ABAS decolorization activities in the presence of l-proline or reduced nicotinamide adenine dinucleotide, while this behavior was not observed in the presence of other amino acids. Moreover, the positive correlation between l-proline concentration and the decolorization activity of membrane proteins was observed, indicating that l-proline plays an important role in ABAS decolorization. The above findings provide us not only a novel insight into bacterial ABAS decolorization, but also an l-proline-supplemented bioaugmentation strategy for enhancing ABAS bio-decolorization.

Immunotoxicity of microplastics and two persistent organic pollutants alone or in combination to a bivalve species.

Both microplastics and persistent organic pollutants (POPs) are ubiquitously present in natural water environment, posing a potential threat to aquatic organisms. While it has been suggested that the immune responses of aquatic organisms could be hampered by exposure to microplastics and POPs, the synergistic immunotoxic impact of these two types of pollutants remain poorly understood. In addition, little is known about the mechanism behind the immunotoxic effect of microplastics. Therefore, in the present study, the immunotoxicity of microplastics and two POPs, benzo[a]pyrene (B[a]P) and 17ß-estradiol (E2), were investigated alone or in combination in a bivalve species, Tegillarca granosa. Evident immunotoxicity, as indicated by alterations of haemocyte count, blood cell composition, phagocytic activity, intracellular content of ROS, concentration of Ca2+ and lysozyme, and lysozyme activity, was revealed for both microplastics and the two POPs examined. In addition, the expression of six immune-, Ca2+ signalling-, and apoptosis-related genes was significantly altered by exposure of clams to the contaminants studied. Furthermore, the toxicity of POPs was generally aggravated by smaller microplastics (500 nm) and mitigated by larger ones (30 µm). This size dependent effect on POP toxicity may result from size dependent interactions between microplastics and POPs. Data obtained in this study also indicate that similar to exposure to B[a]P and E2, exposure to microplastics may hamper the immune responses of clams through a series of interdependent physiological and molecular processes.

Nanoparticles decrease the byssal attachment strength of the thick shell mussel Mytilus coruscus.

The extensive application of nanoparticles (NPs) drives their release into the ocean, which may pose a potential threat to marine organisms. Although the byssus is important for the survival of mussels, the effects of NPs on byssal attachment and the underlying molecular byssal responses remain largely unknown. Therefore, the impacts of three metal oxide NPs (nTiO2, nZnO, and nFe2O3) on the production and mechanical properties of byssal thread in the thick shell mussel M. coruscus were investigated in this study. The results showed that both mechanical properties (such as strength and extensibility) and morphology (diameter and volume) of byssal thread newly produced by M. coruscus were significantly affected after NP exposure, which resulted in an approximately 60-66% decrease in mussel byssal attachment strength. Downregulated expression of genes encoding mussel foot proteins, precursor collagen proteins, and proximal thread matrix proteins was also detected in this study, and this alteration may be one of the reasons for the weakened mechanical properties of byssal threads after NP exposure. This study indicated that NP pollution may hamper byssal attachment of M. coruscus and thereby pose a severe threat to the health of mussel individuals and the stability of the intertidal ecosystem.

Immunotoxicity of four nanoparticles to a marine bivalve species, Tegillarca granosa.

The increasing application of nanomaterials drives the unintentional release of nanoparticles (NPs) into the ocean, which may pose a potential threat to marine organisms. It has been demonstrated that exposure to NPs could chanllenge the immune responses of marine species. However, the affecting mechanism behind remains poorly understood. In this study, the immunotoxic impacts and the mechanisms underpinning the effects of four major NPs, including nZnO, nFe2O3, nCuO, and carbon nanotube (MWCNT), were investigated in blood clam, Tegillarca granosa. The results showed that exposure to tested NPs resulted in reduced total counts, altered cell composition, and constrained phagocytic activities of haemocytes. The intracellular contents of reactive oxygen species (ROS) and the degree of DNA damage of haemocytes were significantly induced, whereas the haemocyte viability was suppressed. Furthermore, NP exposures led to significant increases in the in vivo contents of neurotransmitters. Down-regulations of the immune- and neurotransmitter-related genes were detected as well. Our data suggest that NP exposures hampered the immune responses of blood clams most likely through (1) inducing ROS, causing DNA damage, and reducing cell viability of haemocytes, (2) altering the in vivo contents of neurotransmitters, and (3) affecting the expression of immune- and neurotransmitter-related genes.

Fluoxetine suppresses the immune responses of blood clams by reducing haemocyte viability, disturbing signal transduction and imposing physiological stress.

The antidepressant fluoxetine (FLX), a selective serotonin reuptake inhibitor, is widely prescribed for the treatment of depression and anxiety disorders. Nowadays, measurable quantities of FLX have been frequently detected in the aquatic ecosystems worldwide, which may pose a potential threat to aquatic organisms. Although the impacts of FLX exposure on immune responses are increasingly well documented in mammals, they remain poorly understood in aquatic invertebrates. Therefore, to gain a better understanding of the ecotoxicological effects of FLX, the impacts of waterborne FLX exposure on the immune responses of blood clam, Tegillarca granosa, were investigated in this study. Results obtained showed that both cellular and humoural immune responses in T. granosa were suppressed by exposure to waterborne FLX, as indicated by total counts of haemocytes (THC), phagocytic rate, and activities of superoxide dismutases (SOD) and catalase (CAT), suggesting that waterborne FLX renders blood clams more vulnerable to pathogen challenges. To ascertain the mechanisms explaining how waterborne FLX affects immune responses, haemocyte viabilities, intracellular Ca2+ levels, in vivo concentrations of neurotransmitters, physiological stress conditions (as indicated by in vivo concentrations of cortisol), and expressions of key regulatory genes from Ca2+ and neurotransmitter signal transduction, as well as immune-related signalling pathways, were examined after 10 days of FLX exposure by blood clams via 1, 10 and 100 µg/L waterborne FLX. The results obtained indicated that immune response suppression caused by waterborne FLX could be due to (i) inhibited haemocyte viabilities, which subsequently reduce the THC; (ii) altered intracellular Ca2+ and neurotransmitter concentrations, which lead to constrained phagocytosis; and (iii) aggravated physiological stress, which thereafter hampers immune-related NFκB signalling pathways.

Anthropogenic Noise Aggravates the Toxicity of Cadmium on Some Physiological Characteristics of the Blood Clam Tegillarca granosa.

Widespread applications of cadmium (Cd) in various products have caused Cd contamination in marine ecosystems. Meanwhile, human activities in the ocean have also generated an increasing amount of noise in recent decades. Although anthropogenic noise and Cd contaminants could be present simultaneously in marine environments, the physiological responses of marine bivalve mollusks upon coexposure to anthropogenic noise and toxic metal contaminants, including Cd remain unclear. Therefore, the combined effects of anthropogenic noise and Cd on the physiological characteristics of the blood clam Tegillarca granosa were investigated in this study. The results showed that 10 days of coexposure to anthropogenic noise and Cd can enhance adverse impacts on metabolic processes, as indicated by the clearance rate, respiration rate, ammonium excretion rate, and O:N ratio of T. granosa. In addition, both the ATP content, ATP synthase activity and genes encoding important enzymes in ATP synthesis significantly declined after coexposures to anthropogenic noise and Cd, which have resulted from reduced feeding activity and respiration. Furthermore, the expressions of neurotransmitter-related genes (MAO, AChE, and mAChR3) were all significantly down-regulated after coexposure to anthropogenic noise and Cd, which suggests an enhanced neurotoxicity under coexposure. In conclusion, our study demonstrated that anthropogenic noise and Cd would have synergetic effects on the feeding activity, metabolism, and ATP synthesis of T. granosa, which may be due to the add-on of stress responses and neurotransmitter disturbances.

Exogenous Ca2+ mitigates the toxic effects of TiO2 nanoparticles on phagocytosis, cell viability, and apoptosis in haemocytes of a marine bivalve mollusk, Tegillarca granosa.

Phagocytosis suppression induced by nanoparticles (NPs) exposure is increasingly reported in marine species. However, the mechanisms underlying this impact remain poorly understood. In order to improve our present understanding of the immunotoxicity of NPs, acute (96 h) TiO2 NP exposure and rescue trials via exogenous supply of Ca2+ were performed in the blood clam, Tegillarca granosa. The results show that the phagocytosis rate, cell viability, and intracellular Ca2+ concentration of haemocytes were significantly suppressed, whereas the intracellular ROS concentration of haemocytes significantly increased upon nTiO2 exposure. Exposure to nTiO2 also led to the significant downregulation of Caspase-3, Caspase-6, apoptosis regulator Bcl-2, Bcl-2-associated X, calmodulin kinase II, and calmodulin kinase kinase II. Furthermore, the toxic impacts of nTiO2 were partially mitigated by the addition of exogenous Ca2+, as indicated by the recovery tendency in almost all the measured parameters. The present study indicates that Ca2+ signaling could be one of the key pathways through which nTiO2 attacks phagocytosis.

Neurotoxic impact of acute TiO2 nanoparticle exposure on a benthic marine bivalve mollusk, Tegillarca granosa.

The release of nanoparticles (NPs) into the ocean inevitably poses a threat to marine organisms. However, to date, the neurotoxic effects of NPs remains poorly understood in marine bivalve species. Therefore, in order to gain a better understanding of the physiological effects of NPs, the impact of acute (96 h) TiO2 NP exposure on the in vivo concentrations of three major neurotransmitters, the activity of AChE, and the expression of neurotransmitter-related genes was investigated in the blood clam, Tegillarca granosa. The obtained results showed that the in vivo concentrations of the three tested neurotransmitters (DA, GABA, and ACh) were significantly increased when exposed to relatively high doses of TiO2 NPs (1 mg/L for DA and 10 mg/L for ACh and GABA). Additionally, clams exposed to seawater contaminated with TiO2 NP had significantly lower AChE activity. In addition, the expression of genes encoding modulatory enzymes (AChE, GABAT, and MAO) and receptors (mAChR3, GABAD, and DRD3) for the neurotransmitters tested were all significantly down-regulated after TiO2 NP exposure. Therefore, this study has demonstrated the evident neurotoxic impact of TiO2 NPs in T. granosa, which may have significant consequences for a number of the organism's physiological processes.