Shanjie Zha

Benzo[a]pyrene exposure under future ocean acidification scenarios weakens the immune responses of blood clam, Tegillarca granosa

Abstract Persistent organic pollutants (POPs) are known to converge into the ocean and accumulate in the sediment, posing great threats to marine organisms such as the sessile bottom burrowing bivalves. However, the immune toxicity of POPs, such as B[a]P, under future ocean acidification scenarios remains poorly understood to date. Therefore, in the present study, the impacts of B[a]P exposure on the immune responses of a bivalve species, Tegillarca granosa, under present and future ocean acidification scenarios were investigated. Results obtained revealed an increased immune toxicity of B[a]P under future ocean acidification scenarios in terms of reduced THC, altered haemocyte composition, and hampered phagocytosis, which may attribute to the synergetic effects of B[a]P and ocean acidification. In addition, the gene expressions of pathogen pattern recognition receptors (TLR1, TLR2, TLR4, TLR6), pathway mediators (TRAF6, TAK1, TAB2, IKK&agr; and Myd88), and effectors (NF‐&kgr;B) of the important immune related pathways were significantly down‐regulated upon exposure to B[a]P under future ocean acidification scenarios. Results of the present study suggested an increased immune toxicity of B[a]P under future ocean acidification scenarios, which will significantly hamper the immune responses of T. granosa and subsequently render individuals more susceptible to pathogens challenges. Graphical abstract Figure. No Caption available. HighlightsIncreased immune toxicity of B[a]P under future ocean acidification scenarios.Synergetic effects of B[a]P and OA on THC, haemocyte composition, phagocytosis.B[a]P under future OA scenarios down‐regulated expression of immune related genes.

Immunotoxicity of nanoparticle nTiO2 to a commercial marine bivalve species, Tegillarca granosa

Abstract The increasing production and extensive application of nanoparticles (NPs) inevitably leads to increased release of NPs into the marine environment and therefore poses a potential threat to marine organisms, especially the sessile benthic bivalves. However, the impacts of NPs on the immunity of commercial and ecological important bivalve species, Tegillarca granosa, still remain unknown to date. In addition, the molecular mechanism of the immunotoxicity of NPs still remains unclear in marine invertebrates. Therefore, the immunotoxicity of nTiO2 exposure to T. granosa at environmental realistic concentrations was investigated in the present study. Results obtained showed that the total number, phagocytic activity, and red granulocytes ratio of the haemocytes were significantly reduced after 30 days nTiO2 exposures at the concentrations of 10 and 100 &mgr;g/L. Furthermore, the expressions of genes encoding Pattern Recognition Receptors (PPRs) and downstream immune‐related molecules were significantly down‐regulated by nTiO2 exposures, indicating a reduced sensitivity to pathogen challenges. In conclusion, evident immunotoxicity of nTiO2 to T. granosa at environmental realistic concentrations was detected by the present study. In addition, the gene expression analysis suggests that the PRRs (both TLRs and RIG1 investigated) may be the molecules for NPs recognition in marine invertebrates. Graphical abstract Figure. No Caption available. HighlightsTiO2 NPs leads to a reduction in total haemocytes counts and phagocytosis.Blood cell type composition is altered after TiO2 NPs exposure.TiO2 NPs exposure down‐regulates immune‐related genes.TiO2 NPs weakens immune responses of blood clam.

Effects of reduced pH and elevated pCO2 on sperm motility and fertilisation success in blood clam, Tegillarca granosa

ABSTRACT Although it has been shown that ocean acidification generally has a negative impact on fertilisation success of broadcast spawning marine organisms, whether induced fertilisation success reduction is a consequence of elevated pCO2 or decreased pH remains unclear. Therefore, the impacts of HCl- and CO2-induced acidified seawater on sperm motility and gametes fertilisation capability of a broadcast spawning bivalve species, Tegillarca granosa were investigated in the present study. The results showed that the fertilisation capability of both gametes was significantly reduced in either HCl- or CO2-acidified seawater. In addition, significant impacts on sperm motility were observed in the group exposed to CO2-acidified seawater, suggesting that this parameter is sensitive to pCO2 instead of solely pH value. The differences between the two seawater acidification manipulating methods may be due to the intrinsic difference in diffusion capability of CO2 and protons.

Waterborne Cd 2+ weakens the immune responses of blood clam through impacting Ca 2+ signaling and Ca 2+ related apoptosis pathways

ABSTRACT 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 &mgr;g/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. HighlightsCd2+ exposure induced a reduction in total haemocytes counts and phagocytosis.Cd2+ exposure affected the expressions of genes from the Ca2+ signaling pathway.Cd2+ exposure influenced the Ca2+‐related apoptosis pathways.Elevated waterborne Ca2+ concentrations can relieve the immunotoxicity of Cd2+.

Ocean Acidification Affects the Cytoskeleton, Lysozymes, and Nitric Oxide of Hemocytes: A Possible Explanation for the Hampered Phagocytosis in Blood Clams, Tegillarca granosa

An enormous amount of anthropogenic carbon dioxide (CO2) has been dissolved into the ocean, leading to a lower pH and changes in the chemical properties of seawater, which has been termed ocean acidification (OA). The impacts of pCO2-driven acidification on immunity have been revealed recently in various marine organisms. However, the mechanism causing the reduction in phagocytosis still remains unclear. Therefore, the impacts of pCO2-driven OA at present and near-future levels (pH values of 8.1, 7.8, and 7.4) on the rate of phagocytosis, the abundance of cytoskeleton components, the levels of nitric oxide (NO), and the concentration and activity of lysozymes (LZM) of hemocytes were investigated in a commercial bivalve species, the blood clam (Tegillarca granosa). In addition, the effects of OA on the expression of genes regulating actin skeleton and nitric oxide synthesis 2 (NOS2) were also analyzed. The results obtained showed that the phagocytic rate, cytoskeleton component abundance, concentration and activity of LZM of hemocytes were all significantly reduced after a 2-week exposure to the future OA scenario of a pH of 7.4. On the contrary, a remarkable increase in the concentration of NO compared to that of the control was detected in clams exposed to OA. Furthermore, the expression of genes regulating the actin cytoskeleton and NOS were significantly up-regulated after OA exposure. Though the mechanism causing phagocytosis seemed to be complicated based on the results obtained in the present study and those reported previously, our results suggested that OA may reduce the phagocytosis of hemocytes by (1) decreasing the abundance of cytoskeleton components and therefore hampering the cytoskeleton-mediated process of engulfment, (2) reducing the concentration and activity of LZM and therefore constraining the degradation of the engulfed pathogen through an oxygen-independent pathway, and (3) inducing the production of NO, which may negatively regulate immune responses.

Laboratory simulation reveals significant impacts of ocean acidification on microbial community composition and host-pathogen interactions between the blood clam and Vibrio harveyi

Abstract It has been suggested that climate change may promote the outbreaks of diseases in the sea through altering the host susceptibility, the pathogen virulence, and the host‐pathogen interaction. However, the impacts of ocean acidification (OA) on the pathogen components of bacterial community and the host‐pathogen interaction of marine bivalves are still poorly understood. Therefore, 16S rRNA high‐throughput sequencing and host‐pathogen interaction analysis between blood clam (Tegillarca granosa) and Vibrio harveyi were conducted in the present study to gain a better understanding of the ecological impacts of ocean acidification. The results obtained revealed a significant impact of ocean acidification on the composition of microbial community at laboratory scale. Notably, the abundance of Vibrio, a major group of pathogens to many marine organisms, was significantly increased under ocean acidification condition. In addition, the survival rate and haemolytic activity of V. harveyi were significantly higher in the presence of haemolymph of OA treated T. granosa, indicating a compromised immunity of the clam and enhanced virulence of V. harveyi under future ocean acidification scenarios. Conclusively, the results obtained in this study suggest that future ocean acidification may increase the risk of Vibrio pathogen infection for marine bivalve species, such as blood clams. HighlightsOcean acidification alters the composition of microbial community.The abundance of Vibrio sp. was increased under acidified condition.OA increase the risk of Vibrio pathogen infection for marine bivalves.

Neurotoxic impact of acute TiO 2 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 organisms physiological processes.

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

&NA; 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 17&bgr;‐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 17&bgr;‐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 NF&kgr;&bgr; 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. HighlightsCo‐exposed to nTiO2 and E2 induced a reduction in total haemocytes counts and phagocytosis.Exposure to nTiO2 and/or E2 affected the expressions of genes from NF&kgr;&bgr; and Toll‐like receptor signaling pathways.Co‐exposure to E2 and nTiO2 led to a significant increase in the content of ALP in hemolymph.nTiO2 enhanced the immunotoxicity of E2 to the blood clam through increasing E2 uptake.

Ageing reduces the reproductive performance of male white shrimp Litopenaeus vannamei by altering sperm intracellular Ca2+ concentrations and interfering with sperm apoptosis

Although the effects of age on the reproductive performance of various invertebrates, including white shrimp Litopenaeus vannamei are increasingly well documented, the mechanisms manifesting these impacts remain poorly understood. To ascertain the mechanisms of age on reproductive performance, the sperm quality, intracellular contents of Ca2+, insemination and hatching rates, and status of sperm apoptosis in terms of the expression of key regulatory genes were investigated in 11 and 16 month old male L. vannamei. The aged male individuals (16 months) had lesser reproductive performance in terms of fertilization and hatching rates. In addition, fewer and less viable sperm were detected in aged shrimp, which may be due to the altered expression of apoptosis-related genes. Furthermore, the aged males had lesser intracellular contents of Ca2+ in the sperm which may decrease the capacity of these gametes to undergo a complete acrosome reaction. In general, due to the decrease in intracellular contents of Ca2+ and alterations in the process of apoptosis, aged L. vannamei have relatively lesser quality sperm and may, therefore, have lesser reproductive performance.