AChE inhibition: one dominant factor for swimming behavior changes of Daphnia magna under DDVP exposure

Combined effect and mechanism of microplastic with different particle sizes and levofloxacin on developing Rana nigromaculata: Insights from thyroid axis regulation and immune system

Microplastics (MPs) usually appear in the aquatic environment as complex pollutants with other environmental pollutants, such as levofloxacin (LVFX). After 45-day exposure to LVFX and MPs with different particle sizes at environmental levels, we measured the weight, snout-to-vent length (SVL), and development stages of Rana nigromaculata. Furthermore, we analyzed proteins and genes related to immune system and thyroid axis regulation, intestinal histological, and bioaccumulation of LVFX and MPs in the intestine and brain to further explore the toxic mechanism of co-exposure. We found MPs exacerbated the effect of LVFX on growth and development, and the order of inhibitory effects is as follows: LVFX-MP3>LVFX-MP1>LVFX-MP2. 0.1 and 1 μm MP could penetrate the blood-brain barrier, interact with LVFX in the brain, and affect growth and development by regulating thyroid axis. Besides, LVFX with MPs caused severer interference on thyroid axis compared with LVFX alone. However, 10 μm MP was prone to accumulating in the intestine, causing severe histopathological changes, interfering with the intestinal immune system and influencing growth and development through immune enzyme activity. Thus, we concluded that MPs could regulate the thyroid axis by interfering with the intestinal immune system.

Cardiotoxic and neurobehavioral effects of sucralose and acesulfame in Daphnia: Toward understanding ecological impacts of artificial sweeteners

Artificial sweeteners are widely used in food and pharmaceuticals, but their stability and persistence raise concerns about their impact on aquatic life. Although standard toxicity tests do not reveal lethal effects, recent studies suggest a potential neurotoxic mode of action. Using environmentally relevant concentrations, we assessed the effects of sucralose and acesulfame, common sugar substitutes, on Daphnia magna focusing on biochemical (acetylcholinesterase activity; AChE), physiological (heart rate), and behavioural (swimming) endpoints. We found dose-dependent increases in AChE and inhibitory effects on heart rate and behaviour for both substances. Moreover, acesulfame induced a biphasic response in AChE activity, inhibiting it at lower concentrations and stimulating at higher ones. For all endpoints, the EC50 values were lower for acesulfame than for sucralose. Additionally, the relationship between acetylcholinesterase and heart rate differed depending on the substance, suggesting possible differences in the mode of action between sucralose and acesulfame. All observed EC50 values were at μg/l levels, i.e., within the levels reported for wastewater, with adverse effects observed at as low as 0.1 μg acesulfame /l. Our findings emphasise the need to re-evaluate risk assessment thresholds for artificial sweeteners and provide evidence for the neurotoxic effects of artificial sweeteners in the environment, informing international regulatory standards.

Influence of sucralose, acesulfame-k, and their mixture on brain's fish: A study of behavior, oxidative damage, and acetylcholinesterase activity in Daniorerio

Sucralose (SUC) and acesulfame-k (ACE-K) are widely used artificial sweeteners worldwide; however, they are frequently detected in aquatic environments due to their low metabolism and inadequate removal during wastewater treatment. The harmful effects of these compounds on hydrobionts have yet to be fully understood, as data on their toxicity is limited and inconclusive. This research aimed to determine the impact of SUC (50, 75, 125 μg/L) and ACE-K (50, 75, 125 μg/L), individually and in combination, on fish's swimming behavior, acetylcholinesterase activity, and oxidative stress response after four months of exposure. Following exposure, adult Danio rerio displayed anxiety-like behavior, as evidenced by increased freezing time and decreased swimming activity. Additionally, analysis of fish brain tissue revealed a disruption of REDOX homeostasis, leading to oxidative stress, which may be responsible for the observed inhibition of AChE activity. The results indicated that ACE-K was more toxic than SUC, and the mixture of both compounds produced a more detrimental effect than when each compound was administered alone. These findings highlight the hazardous impacts of SUC and ACE-K on fish in environmentally relevant concentrations, suggesting that these compounds should be added to the priority pollutant list.

A novel approach for the assessment of invertebrate behavior and its use in behavioral ecotoxicology

Sublethal effects are becoming more relevant in ecotoxicological test methods due to their higher sensitivity compared to lethal endpoints and their preventive nature. Such a promising sublethal endpoint is the movement behavior of invertebrates which is associated with the direct maintenance of various ecosystem processes, hence being of special interest for ecotoxicology. Disturbed movement behavior is often related to neurotoxicity and can affect drift, mate-finding, predator avoidance, and therefore population dynamics. We show the practical implementation of the ToxmateLab, a new device that allows monitoring the movement behavior of up to 48 organisms simultaneously, for behavioral ecotoxicology. We quantified behavioral reactions of Gammarus pulex (Amphipoda, Crustacea) after exposure to two pesticides (dichlorvos and methiocarb) and two pharmaceuticals (diazepam and ibuprofen) at sublethal, environmentally relevant concentrations. We simulated a short-term pulse contamination event that lasted 90 min. Within this short test period, we successfully identified behavioral patterns that were most pronounced upon exposure to the two pesticides: Methiocarb initially triggered hyperactivity, after which baseline behavior was restored. On the other hand, dichlorvos induced hypoactivity starting at a moderate concentration of 5 μg/L - a pattern we also found at the highest concentration of ibuprofen (10 μg/L). An additional acetylcholine esterase inhibition assay revealed no significant impact of the enzyme activity that would explain the altered movement behavior. This suggests that in environmentally realistic scenarios chemicals can induce stress - apart from mode-of-action - that affects non-target organisms' behavior. Overall, our study proves the practical applicability of empirical behavioral ecotoxicological approaches and thus represents a next step towards routine practical use.

Acute toxicity of tire wear particles and leachate to Daphnia magna

Tire wear particles (TWP) are a new pollutant widely present in the environment, and have been identified as microplastics (MPs), which are receiving increasing attention due to their toxic effects on aquatic organisms. In this study, D. magna was used as test organism, and the leachate from TWP was prepared by hot water extraction for 30 (30-E) and 120 min (120-E). The acute toxic effects of particles and leachate on D. magna were studied under different exposure concentrations. The results showed that zinc and pyrene were the highest detected contaminants in the leachate. The 48 h-LC50 values for particles and leachate were determined to be 56.99, 461.30 (30-E), and 153.00 mg/L (120-E), respectively. Following a 48 h exposure period, the immobilization of D. magna exposed to the particles and their leachate were increased with the concentration increase. The physical damage of the gut was found to be a possible mechanism for particle-induced biotoxicity. The compounds leached from TWP were responsible for the acute toxicity of leachate. Particles usually demonstrated a greater degree of toxicity in comparison to their leachate, especially at environmentally relevant concentrations. Exposure to particles and leachate resulted in the inhibition of swimming speed, swimming acceleration, filtration rate, and ingestion rate in D. magna. Furthermore, thoracic limb activity was observed to be inhibited. The heart rate of D. magna was significantly increased by the presence of particles at a concentration of 200 mg/L and leachate at concentrations of 400 and 800 mg/L (120-E). The observed alterations in behavior and physiological endpoints may be related to oxidative stress and neurotoxicity in the organism. Reduced superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) activities indicated that D. magna may suffer from excessive oxidative stress, whereas the increase of acetylcholinesterase (AChE) activity may serve as a biomarker of susceptibility to evaluate the environmental risks of TWP and corresponding leachates as potential aquatic pollutants.. Therefore, a more comprehensive risk assessment of TWP in the environment is necessary.

Multi-level biological responses of Daphnia magna exposed to settleable atmospheric particulate matter from metallurgical industries

Metallurgical industries are a continuous source of air pollution due to the amount of settleable particulate matter (SePM) they release. This SePM is a complex mixture formed by metallic nanoparticles and metals, which reach terrestrial and aquatic ecosystems and can be a significant source of contamination. The aim of this study was to evaluate the adverse effects of SePM at different levels of biological organization in order to estimate its ecological impacts on aquatic ecosystems. For this purpose, the crustacean Daphnia magna was exposed to different concentrations of SePM (0.01, 0.1, 1, 5, 10 g/L) using a multi-level response approach. The endpoints studied were: avoidance throughout 24 h in a non-forced exposure system, reproduction (total number of neonates per female after 21 days of exposure), acetylcholinesterase activity (AChE) after 48 h, and finally, the feeding rates during a short-term exposure (48 h) and a long-term exposure (21 day + 48 h). There was a negative effect of SePM on all responses measured at high concentrations. The avoidance was concentration-dependent and represented 88 % and 100 % at the two highest concentrations. The AChE activity was significantly inhibited at 5 and 10 g/L. The total number of neonates increased from 1 g/L of SePM and the first brood occurred earlier as of 5 g/L compared to control. The post-exposure feeding rates were lower during long-term exposure at the highest concentration. Chemical analyses were performed to characterize the metals present in this SePM, but this study did not report any direct relationship with toxicity, due to the chemical heterogeneity of the particles. The emission of compounds caused by anthropogenic activity may have significant ecological consequences, so it is important to consider these possible effects on aquatic biota generated by the mixture of metals present in SePM originated from metallurgical activities. Environmental and sectorial regulations are needed to prevent contamination and ecological disturbances.

Anodonta cygnea, a freshwater swan mussel, exposed to diazinon: toxicity thresholds in behaviour and physiology

Swan mussels (Anodonta cygnea) have been suggested as suitable bioindicators for the presence of pollutants in the environment. Application of the physiological and behavioral markers in these sessile species can be beneficial for environmental monitoring. The present study aimed to investigate the relationship between the behavioral disorders of movement and siphoning associated with the inhibition of tissue Acetylcholinesterase (AChE). For experiments, overally 120 bivalves of Anodonta cygnea (mean total length 80.33 ± 6.7 mm) were transported from the agricultural drains and canals in Sari county (Mazandaran Province, Iran) to our laboratory. First, the LC50-96 h of diazinon was estimated according to the Organization for Economic Co-operation and Development (OECD 1992) guideline with static water conditions. The sub-lethal toxicity pesticide experiments were conducted on the basis of the lowest observed effect concentration (LOEC) and the maximum acceptable toxicant concentration (MATC). The LC50-96 h, LOEC, and MATC values of diazinon were 85.2, 42.1, and 8.5 mg L- 1, respectively. Based on the observations of mussels' movement, the burrowing and displacement decreased with the concentration of toxicant in water. Moreover, the presence of diazinon in water and its exposure to experimental animals significantly reduces their siphoning rate. The RDA showed that the AChE activity had a higher correlation with the siphoning behavior than the movement behavior. The comparison of enzyme activity at different exposure and recovery times showed that there was a significant difference among the groups affected by the consumed pesticide (p = 0.001, between contrasts). The most remarkable morphometric characteristic was the siphon opening that was inversely correlated with the enzymatic activity. Studies in bioethics might benefit from paying attention to these traits that are directly related to the level of toxicity and behavioral adaptations required for animal survival.

Comprehensive assessment of the ecological risk of exposure to triphenyl phosphate in a bioindicator tadpole

The toxicity of triphenyl phosphate (TPhP) to aquatic organisms in surface waters has been demonstrated; However, an understanding of toxicity profiles of TPhP in amphibians is limited. Therefore, the adverse effects and threshold concentrations of TPhP on metamorphosis, growth, locomotion, and hepatic antioxidants of Gosner stage 25 Polypedates megacephalus tadpoles under long-term (35 d) exposure to six TPhP concentrations until complete metamorphosis were assessed. Additionally, the overall effect of using integrated multiple biomarkers were determined to demonstrate the potential ecological risks of waterborne TPhP at environmentally relevant concentrations in amphibian tadpoles. With increasing TPhP concentrations, physical parameters (snout-vent length, body mass, condition factor, and hepatic somatic index), jumping distance, hepatic catalase, and superoxide dismutase activities decreased, whereas metamorphosis time and malondialdehyde content increased. The threshold concentration of TPhP that affected the tadpole biomarker, except for metamorphosis rate and jumping distance, was 50-400 μg/L. Furthermore, the standardized scores of the examined integrated biomarkers in the six TPhP concentrations were visualized using radar plots and calculated as the integrated biomarker responses (IBRs). The varying TPhP concentrations had different scores in the radar plots, and the threshold for affecting the IBR value was 10 μg/L, which was close to the TPhP concentration in surface waters. Additionally, IBR values were strongly positively correlated with the TPhP concentrations. These findings indicate that environmentally relevant exposure to waterborne TPhP can pose an ecological risk to amphibian tadpoles. This study can serve as a reference and assist in the formulation of relevant policies and strategies to control TPhP pollution in water bodies.

Chronic exposure to realistic concentrations of metformin prompts a neurotoxic response in Danio rerio adults

Metformin (MET) is among the most consumed drugs around the world, and thus, it is considered the uppermost drug in mass discharged into water settings. Nonetheless, data about the deleterious consequences of MET on water organisms are still scarce and require further investigation. Herein, we aimed to establish whether or not chronic exposure to MET (1, 20, and 40 μg/L) may alter the swimming behavior and induce neurotoxicity in Danio rerio adults. After 4 months of exposure, MET-exposed fish exhibited less swimming activity when compared to control fish. Moreover, compared with the control group, MET significantly inhibited the activity of AChE and induced oxidative damage in the brain of fish. Concerning gene expression, MET significantly upregulated the expression of Nrf1, Nrf2, BAX, p53, BACE1, APP, PSEN1, and downregulated CASP3 and CASP9. Although MET did not overexpress the CASP3 gene, we saw a meaningful rise in the activity of this enzyme in the blood of fish exposed to MET compared to the control group, which we then confirmed by a high number of apoptotic cells in the TUNEL assay. Our findings demonstrate that chronic exposure to MET may impair fish swimming behavior, making them more vulnerable to predators.

Metal contamination and heat stress impair swimming behavior and acetylcholinesterase activity in embryo-larval stages of the Mediterranean mussel, Mytilus galloprovincialis

Behavioral parameters are increasingly considered sensitive and early bioindicators of toxicity in aquatic organisms. A video-tracking tool was specifically developed to monitor the swimming behaviour of D-larvae of the Mediterranean mussel, Mytilus galloprovincialis, in controlled laboratory conditions. Both maximum and average swimming speeds and trajectories were recorded. We then investigated the impact of copper and silver with or without a moderate rise of temperature on swimming behavior and acetylcholinesterase (AChE) activity of mussel D-larvae and the possible mechanistic link between both biological responses. Our results showed that copper and/or silver exposure, as well as temperature increase, disrupts the swimming behavior of mussel larvae which could compromise their dispersal and survival. In addition, the combined effect of temperature and metals significantly (p < 0.05) increased AChE activity in mussel larvae. Pearson's correlation analysis was performed and results showed that the AChE activity is positively correlated with maximum speeds (r = 0.71, p < 0.01). This study demonstrates the value of behavioral analyzes of aquatic invertebrates as a sensitive and integrate marker of the effects of stressors.

Chronic exposure to environmentally relevant concentrations of guanylurea induces neurotoxicity of Danio rerio adults

Recent studies have shown guanylurea (GUA) alters the growth and development of fish, induces oxidative stress, and disrupts the levels and expression of several genes, metabolites, and proteins related to the overall fitness of fish. Nonetheless, up to date, no study has assessed the potential neurotoxic effects that GUA may induce in non-target organisms. To fill the current knowledge gaps about the effects of this metabolite in the central nervous system of fish, we aimed to determine whether or not environmentally relevant concentrations of this metabolite may disrupt the behavior, redox status, AChE activity in Danio rerio adults. In addition, we also meant to assess if 25, 50, and 200 μg/L of GUA can alter the expression of several antioxidant defenses-, apoptosis-, AMPK pathway-, and neuronal communication-related genes in the brain of fish exposed for four months to GUA. Our results demonstrated that chronic exposure to GUA altered the swimming behavior of D. rerio, as fish remained more time frozen and traveled less distance in the tank compared to the control group. Moreover, this metabolite significantly increased the levels of oxidative damage biomarkers and inhibited the activity of acetylcholinesterase of fish in a concentration-dependent manner. Concerning gene expression, environmentally relevant concentrations of GUA downregulated the expression GRID2IP, PCDH17, and PCDH19, but upregulated Nrf1, Nrf2, p53, BAX, CASP3, PRKAA1, PRKAA2, and APP in fish after four months of exposure. Collectively, we can conclude that GUA may alter the homeostasis of several essential brain biomarkers, generating anxiety-like behavior in fish.

Detoxification and recovery after cadmium exposure in the freshwater crab Sinopotamon henanense

Cadmium (Cd) is a common pollutant in the aquatic environment, which puts the health and safety of aquatic organisms and humans at risk. In the present study, the freshwater crab Sinopotamon henanense was exposed to Cd (0, 50, 100, and 500 μg·L^-1) for 14 d (0-14th d), followed by 21 d (14-35th d) of depuration. The changes in Cd bioaccumulation, microstructure, biomacromolecules (polysaccharides, neutral lipids, DNA and total proteins), and biochemical parameters (SOD, CAT, GR, TrxR, MDA and AChE) in the gills and hepatopancreas were tested. The injured microstructure, activated antioxidant system, increased MDA, and inhibited AChE of the gills and hepatopancreas responded with progressive bioaccumulation of Cd. Meanwhile, the polysaccharides and neutral lipids in the hepatopancreas reduced and DNA synthesis enhanced. During depuration, more than 58.80 ± 8.53% and 13.84 ± 12.11% of Cd was excreted from the gills and hepatopancreas, respectively. Recovery of microstructure and biomacromolecules as well as alleviated oxidative damage and neurotoxicity were also found in these two organs. Additionally, based on PCA, I_his, GR and MDA were identified as the optimal biomarkers indicating the health status of crabs. In conclusion, S. henanense could resist Cd stress through antioxidant defence and self-detoxification.

Physiological and transcriptomic changes of zebrafish (Danio rerio) embryos-larvae in response to 2-MIB exposure

2-Methylisoborneol (2-MIB), a natural odorous substance, is widely distributed in water environment, but there is a paucity of information concerning its systemic toxicity. Herein, we investigated the effects of 2-MIB exposure on developmental parameters, locomotive behavior, oxidative stress, apoptosis and transcriptome of zebrafish. Zebrafish embryos exposed to different concentrations (0, 0.5, 5 and 42.8 μg/L) of 2-MIB showed no changes in mortality, hatchability, and malformation rate, but the body length of zebrafish larvae was significantly increased in a dose-dependent manner, and accompanied by the changes of growth hormone/insulin-like growth factor (GH/IGF) axis and the hypothalamic-pituitary-thyroid (HPT) axis genes. Moreover, the swimming activity of zebrafish larvae increased, which may be due to the increase of acetylcholinesterase (AChE) activity. Meanwhile, 2-MIB caused oxidative stress and apoptosis in zebrafish larvae by altering the NF-E2-related factor 2 (Nrf2) and mitochondrial signaling pathways, respectively. Transcriptome sequencing assay showed that the phototransduction signaling pathway was significantly enriched, and most of the genes in this pathway exhibited enhanced expression after exposure to 2-MIB. These findings provide an important reference for risk assessment and early warning to 2-MIB exposure.

Influence of suspended sediment on the bioavailability of benzophenone-3: Focus on accumulation and multi-biological effects in Daphnia magna

The UV-filter benzophenone-3 (BP3) tends to associate with suspended sediment (SPS) due to hydrophobicity, which could alter its toxicological effects on non-target aquatic organisms. In this study, the freshwater cladoceran Daphnia magna (D. magna) was selected as a model organism to investigate the impacts of the source and composition of SPS on the accumulation and multiple toxicological effects (from the molecular level to individual level) of BP3. Among the three components of SPS, amorphous organic carbon (AOC) and minerals promoted the body burden of BP3, while black carbon (BC) inhibited the bioaccumulation. The inhibition effects of BP3 on swimming and feeding behaviors of D. magna were also enhanced due to the presence of AOC and BC. Compared with BP3 exposure alone, higher oxidative stress and neurotoxicity were observed in the presence of SPS containing AOC, BC and minerals, corresponding to that superoxide dismutase, catalase and glutathione-S-transferase activities were further induced, and acetylcholinesterase activity was inhibited. Furthermore, BP3 induced mRNA expression levels of the endocrine system (ecdysone receptor, cytochrome P450 CYP314) and metabolic system (toxicant nuclear receptor HR96, P-glycoprotein), and the presence of SPS containing AOC, BC and minerals exhibited an enhanced effect. Combined with all endpoints, evident relationship was observed between the bioaccumulation level and the response of individual behavior and molecular biomarkers. The results demonstrated that the effects of SPS compositions on bioaccumulation and toxicological effects of organic UV-filters should be considered in aquatic environments.

The specification of zebrafish (Danio rerio) heart electrocardiogram index characteristic responses to different types of pollutants

Water quality was highly affected by common pollutants. Metals, pesticides and small molecules are ubiquitous pollutants. Advancement in engineering technology (computer-based monitoring systems) increased the efficiency of quantifying toxicity of different chemicals in an organism. The cardiovascular system reflects internal and external stress of an organism, and electrocardiogram (ECG) data reliably measure external stress. As ECG data can accurately reflect the physiological conditions of organisms, and zebrafish (Danio rerio) are considered to be good models for cardiovascular research, it is hypothesized that ECG parameters of zebrafish could indicate the toxicity of water-borne chemicals. To achieve this, we treated zebrafish with different concentrations of target chemicals (CuSO₄, C₁₀H₁₉O₆PS₂ and NH₄Cl) for 48 h and ECG data were measured. P-wave, R-wave, T-wave, PR-interval, QRS-complex and QT-interval data were the focus of this study. The results of self-organizing maps and Pearson correlation analysis indicate that the QRS-complex can be used as an indicator for CuSO₄ stress. The QT-interval could be used to assess the C₁₀H₁₉O₆PS₂ stress. The QT-interval and P-wave can be used to evaluate the NH₄Cl stress. Responses of zebrafish ECG parameters were identical with other vertebrate model, and were specific to toxicant types. It is proved that zebrafish heart ECG index could be used as a potential indicator in early detection of environmental stress.

Central inhibition prevents the in vivo acute toxicity of harmine in mice

BACKGROUND

Harmine is a β-carboline alkaloid that displays antidepressant, antitumor and other pharmacological effects. However, the strong toxic effects limit its clinical application, and should be first considered.

PURPOSE

To evaluate the in vivo toxicity of harmine and explore intervention strategies against its toxicity.

METHODS

The in vivo toxicity of harmine was assessed from the symptoms, biochemical indices, and cardiovascular effects in mice. The intervention experiments were performed by using anesthetics, central drugs, and peripheral anticholinergics.

RESULTS

The acute toxicity of harmine is significantly dose-dependent and the median lethal dose is 26.9 mg/kg in vivo. The typical symptoms include convulsion, tremor, jumping, restlessness, ataxia, opisthotonos, and death; it also changes cardiovascular function. The anesthetics improved the survival rate and abolished the symptoms after harmine poisoning. Two central inhibitors, benzhexol and phenytoin sodium, uniformly improved the survival rates of mice poisoned with harmine. The peripheral anticholinergics didn't show any effects.

CONCLUSION

Harmine exposure leads to central neurological symptoms, cardiovascular effects and even death through direct inhibition of the central AChE activity, where the death primarily comes from central neurological symptoms and is cooperated by the secondary cardiovascular collapse. Central inhibition prevents the acute toxicity of harmine, and especially rapid gaseous anesthetics such as isoflurane, might have potential application in the treatment of harmine poisoning.

Characterization of neurotransmitters and related metabolites in Daphnia magna juveniles deficient in serotonin and exposed to neuroactive chemicals that affect its behavior: A targeted LC-MS/MS method

Neurotransmitters are endogenous metabolites that play a crucial role within an organism, at the chemical synapses. There is a growing interest in their analytical determination for understanding the neurotoxic effect of contaminants. Daphnia magna represents an excellent aquatic model for these environmental studies, due to its similarities with vertebrates in several neurotransmitters and related gene pathways and because of its wide application in ecotoxicological studies. Within this study, an accurate and sensible method of analysis of 17 neurotransmitters and related precursors and metabolites was developed. The method was validated in terms of sensitivity, reproducibility, precision, and accuracy, and also matrix effect was evaluated. As an independent probe of method validation and applicability, the method was applied to two different scenarios. First, it was used for the study of neurotransmitter levels in genetically mutated tryptophan hydrolase D. magna clones, confirming the absence of serotonin and its metabolite 5-HIAA. Additionally, the method was applied for determining the effects of chemical compounds known to affect different neurotransmitter systems and to alter Daphnia behavior. Significant changes were observed in 13 of the analyzed neurotransmitters across treatments, which were related to the neurotransmitter systems described as being affected by these neurochemicals. These two studies, which provide results on the ways in which the neurotransmitter systems in D. magna are affected, have corroborated the applicability of the presented method, of great importance due to the suitability of this organism for environmental neurotoxicity studies.

Simultaneous eco-toxicity assessment technique using an online monitoring system: effects of different environmental factors on swimming behavior of zebrafish (Danio rerio)

Environmental factors, such as photoperiod and temperature were the main limiting factors for the survival of organisms in the nature environment. Changes in environmental factors are well predicted but determining their effects on organisms are challenging hot topic in the field of eco-toxicology. Thus, technology based eco-toxicity assessment was focused worldwide. In this research, the effects of different temperatures (15 °C, 22 °C, 30 °C, 32 °C, and 35 °C) and photoperiods (dark and light periods) on the continuous behavior responses of Zebrafish (Danio rerio) were investigated using an online monitoring system (OMS). We designed a new fish chamber with sensors to measure the behavior responses of zebrafish under different conditions. Data obtained from the OMS could be assessed for factors such as difference in swimming behavior, circadian rhythm, and avoidance behavior using latest software (MATLAB). The observed behavior anomalies on zebrafish under different temperatures and continuous photoperiods were statically significant (p < 0.05). We conclude that the new designed fish chamber (behavior sensors) is good in sensing behavioral responses of zebrafish under different conditions. The fish behavior strength could be a potential biomarker to assess the effects of environmental factors. The present study would be a basic platform for assessing the effects of different stressors simultaneously on swimming behavior of zebrafish.

The potential assessment of green alga Chlamydomonas reinhardtii CC-503 in the biodegradation of benz(a)anthracene and the related mechanism analysis

Benz(a)anthracene (BaA) is a polycyclic aromatic hydrocarbons (PAHs), that belongs to a group of carcinogenic and mutagenic persistent organic pollutants found in a variety of ecological habitats. In this study, the efficient biodegradation of BaA by a green alga Chlamydomonas reinhardtii (C. reinhardtii) CC-503 was investigated. The results showed that the growth of C. reinhardtii was hardly affected with an initial concentration of 10 mg/L, but was inhibited significantly under higher concentrations of BaA (>30 mg/L) (p < 0.05). We demonstrated that the relatively high concentration of 10 mg/L BaA was degraded completely in 11 days, which indicated that C. reinhardtii had an efficient degradation system. During the degradation, the intermediate metabolites were determined to be isomeric phenanthrene or anthracene, 2,6-diisopropylnaphthalene, 1,3-diisopropylnaphthalene, 1,7-diisopropylnaphthalene, and cyclohexanol. The enzymes involved in the degradation included the homogentisate 1,2-dioxygenase (HGD), the carboxymethylenebutenolidase, the ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and the ubiquinol oxidase. The respective genes encoding these proteins were significantly up-regulated ranging from 3.17 fold to 13.03 fold and the activity of enzymes, such as HGD and Rubisco, was significantly induced up to 4.53 and 1.46 fold (p < 0.05), during the BaA metabolism. This efficient degradation ability suggests that the green alga C. reinhardtii CC-503 may be a sustainable candidate for PAHs remediation.

The continuous physiological changes of zebrafish (Danio rerio) based on metabolism under controlled thallium stress

In this research, the continuous physiological changes of zebrafish (Danio rerio) in 0.1 μg/L thallium (Tl) in 15 days were investigated. The results showed that Tl(I) stress had a significant positive linear correlation with zebrafish ammonia nitrogen excretion (ANE) (p < 0.001), and the mean value of ANE in Tl(I) treatment (435 ± 227 mg/kg/h) was approximately 2 times higher than in the control group (239 ± 168 mg/kg/h), which suggested that ANE was suitable for Tl(I) stress assessment. A substantial difference based on oxygen consumption rate (OCR) between the control group (587 ± 112 mg/kg/h) and Tl(I) treatment (260 ± 88 mg/kg/h) with a high significance p < 0.001 could be observed, and the results indicated that Tl(I) played a negative role in OCR of zebrafish. The characteristics of both ANE and OCR changes under slight Tl(I) stress could be reflected by the ammonia quotient (AQ). It was noteworthy that AQ increased rapidly in first 6 h from 0.66 to 4.50, which was 3 times higher than 1.2, indicating rapid increase in both anaerobic energy utilization and protein metabolism in 0.1 μg/L Tl(I) exposure. It is concluded that the physiological changes of zebrafish based on metabolism can be regarded as a sensitive biological indicator of Tl(I) pollution, which could work as a substitute of potassium that disrupts the normal biological metabolism in the process of transport.

Electrophysiological responses in Amazonian fish species Bryconops caudomaculatus (Osteichthyes: Characiformes) as biomarkers of xenobiotic toxicity

Sublethal exposures to environmental pollutants may cause changes in physiological parameters. Thus, knowledge of basal physiological rates of the species and the development of methods to quantify these rates are extremely important. Considering the scarcity of cardiac and muscle physiological studies in native Amazonian fish species and that no evaluation of electrophysiological responses by exposure to a stressor has been reported in Bryconops caudomaculatus, the aim of this study was to develop techniques of electromyographic and electrocardiographic recordings of normal responses, during toxicity induction and short-term recovery. A total of 9 animals were used, divided into two groups: control group (n = 4) and treated group (n = 5), with records lasting 5 min. The results showed that the basal electromyographic records indicate that the studied species has a very intense swimming activity, whereas the basal cardiac parameters clearly showed the patterns in P wave tracing, QRS complex, T wave and Q-T and R-R intervals. During exposure to the stressor, muscle activity ceased presenting intense decrease and myorelaxant effect expected. Electrocardiographic responses confirmed cardiotoxicity with intense bradycardia, ventricular bigeminism, prolongation of QRS complex duration and cardiac arrhythmias, indicating cardiac dysfunction. It was concluded that the electrophysiological responses are excellent biomarkers and showed the susceptibility of the species to the tested substance. In addition, the electrocardiogram and the electromyogram are excellent techniques to reflect the degree of environmental stress when organisms are exposed to toxic substances in the environment.

Potential effects of internal physio-ecological changes on the online biomonitoring of water quality: The behavior responses with circadian rhythms of zebrafish (Danio rerio) to different chemicals

The online biomonitoring of aquatic accidental pollution is very important to realize the assessment of complex toxicity. However, the monitoring results would be affected greatly by the internal physio-ecological changes of test organisms, and circadian rhythms might contribute greatly to this kind of effects. In the present study, the behavior responses of zebrafish (Danio rerio) to different concentrations of Deltamethrin, Atrazine, and Thallium (Tl) in 15 days were investigated using an online behavior monitoring system. The results showed that the average behavior strength (BS) value of dark period (0.71 ± 0.16) was lower than that of light period (0.88 ± 0.09) in the control group. Similar pattern was observed in all other treatments with negative relationship between exposure concentrations and mean BS values. It is concluded that the 24 h circadian rhythms in the behavior responses of zebrafish (Danio rerio) could be observed clearly in the online biomonitoring system, and the online monitoring results would be affected obviously in the characteristics of behavior periodicity abnormal and time delay. Therefore, it is suggested that internal physio-ecological characteristics of organisms must be considered once they have the chance to play roles in bio-induced technologies. More investigations are warranted to clear the effects of internal physio-ecological changes on the exported results.

Behavioural and chronic toxicity of fullerene to Daphnia magna: Mechanisms revealed by transcriptomic analysis

Extensive application of fullerene nanoparticles (nC₆₀) leads to potential environmental pollution. The acute toxic effects of nC₆₀ have been largely investigated, but studies of behavioural and chronic toxicity at sublethal doses are still rare and the underlying molecular mechanisms remain unknown. The present study investigated behavioural and chronic toxicity of nC₆₀ to Daphnia magna. The results showed that, in response to nC₆₀ exposure, hopping, heartbeat frequencies and feeding ability of D. magna decreased significantly, displaying negative relationship with exposure time and dose. Chronic treatments with 0.1 mg/L or 1 mg/L nC₆₀ for 21 days significantly reduced survival and reproduction of D. magna. These harmful effects suggested negative impacts of nC₆₀ on aquatic ecosystems. Moreover, transcriptome analysis showed that the behavioural and chronic toxicity of nC₆₀ to D. magna might be related to physiological functions such as cell structural repair, protein degradation, energy metabolism and reproduction. We found that nC₆₀ accumulated in guts of D. magna, which should be responsible for the decrease of food ingestion and consequently inhibiting energy intake. Deficiency of energy not only affects behaviours but also declines reproduction in D. magna. Overall, this is the first study comprehensively considered the behavioral and chronic toxicity of nC₆₀ to aquatic organism. The results should be helpful to better understand the ecological consequences of C₆₀ released into water environments.

Video-tracking and high-speed bright field microscopy allow the determination of swimming and cardiac effects of D. magna exposed to local anaesthetics

Local anaesthetics are among the most used drugs in clinical practice, but once they are released to the environment, the effects on the aquatic fauna remain uncertain. This study evaluates, for the first time, the impact of tetracaine, lidocaine and bupivacaine on the survival rate and physiological effects of cladocera Daphnia magna. Video-tracking and image processing allowed us to obtain changes in behaviour parameters like swimming average velocity and mean square displacement. We found that tetracaine shows the most severe effect. A high-speed microscopy system was also used to determine the response of D. magna heart to these drugs. Our results show that tetracaine presents dose-dependent area reduction during all cardiac cycle, while bupivacaine and lidocaine did not present significative effects on heart size. The tested drugs, at environmental high concentrations, altered behaviour, heart function and survival of D. magna.

Analysis of neurotransmitters in Daphnia magna affected by neuroactive pharmaceuticals using liquid chromatography-high resolution mass spectrometry

Neurotransmission plays an essential role during the central nervous system (CNS) development. During the last years, several studies based on the changes produced in neurotransmitters of aquatic organisms caused by pharmaceuticals have been reported. Daphnia magna, the aquatic ecotoxicological model organism, shares several of the neurotransmitters targeted by antidepressant and other neuro-active drugs with vertebrates. Therefore, a method based on liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) has been applied for the first time to study the levels of 41 neurotransmitters in Daphnia magna under the effect of four different neuro-active pharmaceuticals (sertraline, venlafaxine, duloxetine and fluoxetine). In addition, the performance of LC-HRMS was studied in terms of linearity, sensitivity, intra- and inter-day precision, and overall robustness. The developed analytical method using LC-HRMS is a new tool for neurotoxicology research using the Daphnia magna model. As a result, general differences on the concentrations of those neurotransmitters exposed to the mentioned pharmaceuticals were observed.

The pathway of 2,2-dichlorovinyl dimethyl phosphate (DDVP) degradation by Trichoderma atroviride strain T23 and characterization of a paraoxonase-like enzyme

Dichlorvos (DDVP) is widely applied in the agricultural industry, and its residues are considered hazardous to the environment. Microbial bioremediation is an innovative technology with the potential to mitigate such pollution. Trichoderma atroviride strain T23, a filamentous fungus, is very efficient at degrading DDVP. Therefore, we used DDVP as a model organophosphate pesticide to study the mechanism by which Trichoderma degrades organophosphate pesticides, with the aim of attaining a global understanding of the molecular mechanism of enzymatic degradation of organophosphate pesticides by beneficial fungi. DDVP can be biodegraded via two routes, and the primary one involves hydrolysis of the P-O bond, which can result in the production of the novel degradation intermediate trichloroethanol. TaPon1-like showed continuously high expression during 120 h, and deletion of the gene decreased the efficiency of P-O bond hydrolysis. The enzyme produced by TaPon1-like had a low K_m for DDVP (0.23 mM) and a high k_cat (204.3 s^-1). The enzyme was able to hydrolyze broad substrates such as organophosphate oxons and lactone and maintain stable activity in a wide range of pH and temperature values. The TaPon1-like hydrolase played an important role in the first step of DDVP degradation by strain T23 and contributed to a comprehensive understanding of the mechanism of organophosphate pesticide degradation.

Fish exposed to water contaminated with eprinomectin show inhibition of the activities of AChE and Na+/K+-ATPase in the brain, and changes in natural behavior

The objective of this study was to evaluate whether antiparasitic eprinomectin may be an environmental contaminant in water compartment in low concentrations, negatively affecting neurotransmission and, consequently, the natural behavior of the jundiá (Rhamdia quelen). Fish were randomly allocated in tanks and exposed for 24 and 48 h to eprinomectin concentrations in water [0.0 (Control), 1.124 (T1), 1.809 (T2) and 3.976 (T3) μg L^-1], followed by 48 h of recovery in eprinomectin-free water, in order to evaluate the behavioral parameters, levels of reactive oxygen species (ROS) in the brain, as well as cerebral enzymatic activities of acetylcholinesterase (AChE) and of the sodium-potassium ATPase pump (Na⁺/K⁺-ATPase). Especially at the two highest concentrations of eprinomectin (T2 and T3), the fish showed alterations in natural behavior, particularly hyperlocomotion and longer time on the surface. Furthermore, at these same concentrations, cerebral ROS levels increased and cerebral AChE activity decreased. At the highest concentration (T3) cerebral Na⁺/K⁺-ATPase activity was reduced. Increased ROS and impairment of AChE and Na⁺/K⁺-ATPase enzymes in the brain may have contributed directly to behavioral changes, due to neuronal damage and synapse impairment. Even after 48 h in water without eprinomectin, behavioral changes and neurotoxic effects were observed in fish, suggesting residual effects of the antiparasitic. In conclusion, eprinomectin even in low concentrations may be a hazardous environmental contaminant for aquatic organisms, as it causes brain damage and affects the natural behavior of fish.

Is there a link between acetylcholinesterase, behaviour and density populations of the ragworm Hediste diversicolor?

The main objective of the present study was to explore the potential link between acetylcholinesterase (AChE) activity and burrowing behaviour of the ragworm Hediste diversicolor, which may have consequences at higher levels of biological organisation. Two complementary studies were conducted. AChE activity, at the sub-individual level, and behavioural responses, at the individual level, were evaluated in worms from the Loire estuary (France), whereas density and biomass of H. diversicolor were determined at the population level. A Spearman positive correlation between both biomarkers (AChE and burrowing) suggested that inhibition of AChE activity was linked to behaviour impairments. At the population level, lower AChE and behaviour activities were detected in worms corresponding to lower population density and biomass. These results provide direct empirical field evidence demonstrating the sensitivity of behaviour of H. diversicolor as a biomonitor of estuarine health status assessment.

Using a new high-throughput video-tracking platform to assess behavioural changes in Daphnia magna exposed to neuro-active drugs

Recent advances in imaging allow to monitor in real time the behaviour of individuals under a given stress. Light is a common stressor that alters the behaviour of fish larvae and many aquatic invertebrate species. The water flea Daphnia magna exhibits a vertical negative phototaxis, swimming against light trying to avoid fish predation. The aim of this study was to develop a high-throughput image analysis system to study changes in the vertical negative phototaxis of D. magna first reproductive adult females exposed to 0.1 and 1 μg/L of four neuro-active drugs: diazepam, fluoxetine, propranolol and carbamazepine. Experiments were conducted using a custom designed experimental chamber containing four independent arenas and infrared illumination. The apical-located visible light and the GigE camera located in front of the arenas were controlled by the Ethovision XT 11.5 sofware (Noldus Information Technology, Leesburg, VA). Total distance moved, time spent per zone (bottom vs upper zones) and distance among individuals were analyzed in dark and light conditions, and the effect of different intensities of the apical-located visible light was also investigated. Results indicated that light intensity increased the locomotor activity and low light intensities allowed to better discriminate individual responses to the studied drugs. The four tested drugs decreased the response of exposed organisms to light: individuals moved less, were closer to the bottom and at low light intensities were closer each other. At high light intensities, however, exposed individuals were less aggregated. Propranolol, carbamazepine and fluoxetine induced the most severe behavioural effects. The tested drugs at environmental relevant concentrations altered locomotor activity, geotaxis, phototaxis and aggregation in D. magna individuals in the lab. Therefore the new image analysis system presented here was proven to be sensitive and versatile enough to detect changes in diel vertical migration across light intensities and low concentration levels of neuro-active drugs.

Food up-take and reproduction performance of Daphnia magna under the exposure of Bisphenols

Because the application of Bisphenol A (BPA) was restricted, many substitutes, such as Bisphenol F (BPF) and Bisphenol S (BPS), were developed as BPA substitutes. Therefore, environmental impacts of BPA and its substitutes on aquatic organisms should be concerned, especially their combined toxicity. In this study, the impacts of BPA, BPF, BPS and their mixture on the feeding behavior, reproduction and physiological function of daphnids were synthetically evaluated, involving the duration and mode of exposure. In short-term exposure tests, feeding rates of D. magna decreased after exposure to BPA, BPF, BPS and their mixture, while the inhibition reversed into stimulation in the recovery period. It may benefit from overcompensation of D. magna. In long-term exposure tests, the inhibition effect on the reproduction and growth of the exposed D. magna was difficult to recover, and only some experimental groups have a certain recovery. In conclusion, environmental risk of BPA, BPF, BPS and their mixture on the behavior of D. magna increased with prolonged exposure time. Moreover, relative activities of trypsin, amylase (AMS), acetylcholinesterase (AChE), carbonic anhydrase (CA), glutathione peroxidase (GPx) and super oxidase dimutase (SOD) of the exposed daphnids decreased in most treatment groups, indicating the disorder of digestive, nervous and antioxidative system of D. magna. Interestingly, inhibition of enzymes activities decreased with the increase of the exposure time, which implied the tolerance may be occurred.

Behavior responses of zebrafish (Danio rerio) to aquatic environmental stresses in the characteristic of circadian rhythms

As behavior shows a distinct circadian rhythm, it is hypothesized that circadian rhythms based on zebrafish (Danio rerio) behavior responses could be affected by contaminants in this study, and then the behavior strength of zebrafish exposed to 0.005 mg/L Cadmium chloride (CdCl₂), 0.01 mg/L Dibasic Sodium Phosphate (Na₂HPO₄), 0.002 mg/L deltamethrin, and 0.003 mg/L atrazine for 6 days is used to illustrate the possibility of behavior circadian rhythms as an indicator in the environmental stress assessment. Statistical analysis with p < 0.01 shows that a clear difference between average values of BS during dark period (AVD) and those during light period (AVL) could be observed, and 24 h circadian rhythms do exist in zebrafish behavior responses. Both BS values and circadian rhythms of zebrafish can be affected in the aspect of periodicity with clear time delay, which were 1 h delay in CdCl₂, 4 h delay in Na₂HPO₄, 4 h delay in deltamethrin, and 1 h delay in atrazine. Behavior circadian rhythms were disturbed according to the repetitive cycles after autocorrelation analysis, and the toxic effects of different chemicals could be reflected by the profiles of the Self-Organizing Map (SOM), which indicated the circadian rhythm disorder in different degrees. These results deduced from the statistical analysis, autocorrelation and SOM strongly supported that circadian rhythms based on zebrafish BS could be used as an indicator in the environmental stress assessment.

Environmentally relevant concentrations of di(2-ethylhexyl)phthalate exposure alter larval growth and locomotion in medaka fish via multiple pathways

Di(2-ethylhexyl)phthalate (DEHP) is a commonly used plasticizer, with evidence of ubiquitous human exposure and widespread occurrence in the aquatic environment. It is an emerging environmental pollutant with regulatory priority; however, most studies have focused on the toxicity of DEHP related to endocrine disruption and reproduction in mammals. The ecotoxicological impact of phthalates (e.g., DEHP) on early life stages of fish under environmentally relevant concentrations of chronic exposure remains unclear. In this study, 7-day post-hatching fry of medaka fish (Oryzias latipes) underwent 21-day continuous exposure to DEHP solutions at 20, 100 and 200 μg/L to assess the effects on fish development and locomotion and related toxic mechanisms. Larval mortality was low with DEHP (20-200 μg/L) within 21 days, but such exposure significantly reduced fish body weight and length and altered swimming behavior. At 21 days, DEHP exposure resulted in specific patterns of larval locomotion (e.g., increased maximum velocity and absolute turn angle) and dose-dependently increased the mRNA expression of acetylcholinesterase (ache) but did not alter AChE activity. Transcriptional expression of antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase and peroxisome proliferation-activated receptor and retinoid X receptor genes was significantly suppressed with 21-day DEHP exposure (20-200 μg/L), with marginal alteration in reactive oxygen species levels and antioxidant activities within the dosing period. As well, DEHP altered the mRNA expression of p53-regulated apoptosis pathways, such as upregulated p53, p21 and bcl-2 and downregulated caspase-3 expression, with increased enzymatic activity of caspase-3 in larvae. Our results suggest that toxic mechanisms of waterborne DEHP altered fish growth and locomotion likely via a combined effect of oxidative stress, neurotoxicity and apoptosis pathways.

Soil sustainable utilization technology: mechanism of flavonols in resistance process of heavy metal

The soil ecosystem is critical for agricultural production, affecting many aspects of human health. Soil has more unknown biodiversity and edaphic parameters than any other ecosystem especially when polluted. Metagenomics and metatranscriptomics were applied to research on toxicological characteristics of Pb and resistance mechanism of flavonols. Rhizosphere microorganisms-plants system, a unified system closely related to soil environment was taken as research object. Results emphasize gene expression changes in different test groups. Gene ontology enrichment and eggNOG showed that Pb has a toxic effect on gene and protein function which concentrated on ATPase and ATP-dependent activity. Differentially expressed genes in the flavonols group indicated that flavonols regulate amino acid transport and other transportation process related to Pb stress. Kegg analysis represents that Pb interferences energy production process via not only the upstream like glycolysis and tricarboxylic acid (TCA) circle but also oxidative phosphorylation process, which can also produce reactive oxygen species and impact the eliminating process. Flavonols have shown the ability in alleviating toxic effect of Pb and improving the resistance of plants. Flavonols can recover the electronic transmission and other process in TCA and oxidative phosphorylation via ascorbic acid-glutathione metabolism. Flavonols activated antioxidative process and non-specific immunity via vitamins B₂-B₆ metabolism.

Daphnia swimming behaviour as a biomarker in toxicity assessment: A review

Daphnia is a motile common model organism widely used in ecotoxicological testing. Although mortality and immobilisation are the main endpoints used for determination of toxicity, detection of subtle alterations induced by some chemicals particularly at lower levels may require more sensitive biomarkers. As a number of studies indicated that swimming behaviour may be altered by pesticides, nanoparticles, bacterial products or other chemicals, analysis of its various parameters is considered as a novel methodological approach for toxicity assessment and monitoring of water quality. This paper presents the current state of knowledge on the effects induced by various chemical compounds on the parameters of swimming behaviour of Daphnia and systems developed for its analysis. Advantages and limitations of swimming behaviour as a tool in toxicological studies are also discussed.

Evidence of low dose effects of the antidepressant fluoxetine and the fungicide prochloraz on the behavior of the keystone freshwater invertebrate Gammarus pulex

In recent years, behavior-related endpoints have been proposed as rapid and reliable ecotoxicological tools for risk assessment. In particular, the use of detritivores to test the toxicity of pollutants through feeding is currently becoming a well-known method. Experiments combining feeding with other behavioral endpoints can provide relevant information about direct and indirect toxicological effects of chemicals. We carried out a feeding experiment with the shredder Gammarus pulex in order to detect indirect (through leaf conditioning) and direct effects (through water exposure) of two pollutants at environmentally relevant concentrations: the fungicide prochloraz (6 μg/L) and the antidepressant fluoxetine (100 ng/L). Prochloraz inhibited fungal growth on leaves, but it did not affect either the microbial breakdown rates or the C:N ratio of the leaves. Individuals of G. pulex that were fed with treated leaves presented lower consumption rates, not only those fed with prochloraz-treated leaves, but also those fed with fluoxetine-treated leaves, and those fed with the mixture-treated leaves. Mixed-effects models revealed that the swimming velocity of the amphipods after the experiment was modulated by the exposure to fluoxetine, and also by the exposure to prochloraz. We demonstrate that both the antidepressant and the fungicide may cause significant sublethal effects at low concentrations. The combination of behavioral endpoints together with the application of mixed models provided a useful tool for early detection of the effects of toxicity mixtures in freshwater ecosystems.

The Role of AChE in Swimming Behavior of Daphnia magna: Correlation Analysis of Both Parameters Affected by Deltamethrin and Methomyl Exposure

The unpredictable toxicity of insecticides may cause behavior disorder of biological organisms. In order to assess the role of acetylcholinesterase (AChE) in swimming behavior of Daphnia magna, a correlation analysis of both parameters in 24 h exposure of deltamethrin (DM) and methomyl (MT) was investigated. The behavior responses of D. magna in DM (13.36 μg/L and 33.40 μg/L) and MT (19.66 μg/L and 49.15 μg/L) suggested that recovery behavior in the adjustment phase was crucial, and behavior homeostasis provided them with an optimal way to achieve a wider tolerance against environmental stress. During the experiment, positive effects on AChE activity occurred in the beginning of the exposure. Even though the de novo synthesis of AChE in D. magna might help it recover, the AChE inhibition in different treatments could be observed. Some induction effects on AChE activity at the beginning of exposure occurred, and a 50% decrease may cause toxic effects on behavior. In most treatments, the results showed that both behavior strength and AChE activity stayed in the same field within a correlation circle. These results illustrated that the environmental stress caused by both DM and MT could inhibit AChE activity and subsequently induce a stepwise behavior response, though both pesticides affect it as direct and indirect inhibitors, respectively.

The physiological characteristics of zebra fish (Danio rerio) based on metabolism and behavior: A new method for the online assessment of cadmium stress

In order to illustrate heavy metal ecotoxicology associated with interactions between chemicals and biological systems, we investigated physiological changes (metabolism and behavior response) of zebra fish (Danio rerio) under 48 h Cadmium chloride (CdCl₂) exposure using online monitoring technique. The concentrations of CdCl₂ were designed as 4.26, 42.6 and 85.2 mg/L, which were 0.1, 1.0, and 2.0 based on toxic unit (TU), respectively. The metabolism was assessed using the oxygen consumption (OC), and the behavior response was analyzed in behavior strength (BS). Significant inhibition of both OC and BS could be observed: OC was 617.39 ± 30.48 mg/kg/h in the control, and it decreased rapidly to 229.07 ± 28.66 mg/kg/h in 2.0 TU treatment. BS changed from 0.76 ± 0.07 (control) to 0.39 ± 0.04 (2.0 TU) with the increase of exposure concentrations. Further results suggested that both factors were related to diurnal variation during 48 h exposure, which could be regarded as circadian rhythms: the average values of OC and BS during photo-phase were significantly higher than both during scoto-phase in CdCl₂ treatments (p < 0.05). After integrated analysis, the original values of both OC and BS with wide fluctuation showed a negative linear relationship with CdCl₂ concentration. The levels of both OC and BS were positively correlated with CdCl₂ (r = 0.93 and p < 0.01). It is suggested that both OC and BS provide an objective ground for CdCl₂ stress assessment, and that also could be applied to test the changes of organisms quantitatively in toxic physiology.

Cadmium stress assessment based on the electrocardiogram characteristics of zebra fish (Danio rerio): QRS complex could play an important role

The electrocardiogram (ECG) of zebra fish (Danio rerio) expresses cardiac features that are similar to humans. Here we use sharp microelectrode measurements to obtain ECG characteristics in adult zebra fish and analyze the effects of cadmium chloride (CdCl₂) on the heart. We observe the overall changes of ECG parameters in different treatments (0.1 TU, 0.5 TU and 1.0 TU CdCl₂), including P wave, Q wave, R wave, S wave, T wave, PR interval (atrial contraction), QRS complex (ventricular depolarization), ST segment, and QT interval (ventricular repolarization). The trends of the ECG parameters showed some responses to the concentration and exposure time of CdCl₂, but it was difficult to obtain more information about the useful indicators in water quality assessment depending on tendency analysis alone. A self-organizing map (SOM) showed that P values, R values, and T values were similar; R wave and T wave amplitude were similar; and most important, QRS value was similar to the CdCl₂ stress according to the classified data patterns including CdCl₂ stress (E) and ECG components based on the Ward linkage. It suggested that the duration of QRS complex was related to environmental stress E directly. The specification and evaluation of ECG parameters in Cd²⁺ pollution suggested that there is a markedly significant correlation between QRS complex and CdCl₂ stress with the highest r (0.729) and the smallest p (0.002) among all ECG characteristics. In this case, it is concluded that QRS complex can be used as an indicator in the CdCl₂ stress assessment due to the lowest AIC data abased on the linear regression model between the CdCl₂ stress and ECG parameters.

Does time difference of the acetylcholinesterase (AChE) inhibition in different tissues exist? A case study of zebra fish (Danio rerio) exposed to cadmium chloride and deltamethrin

In order to illustrate time difference in toxic effects of cadmium chloride (CdCl₂) and deltamethrin (DM), AChE activities were measured in different tissues, liver, muscle, brain, and gill, of Zebra fish (Danio rerio) across different concentrations in this research. The average AChE activity decreased comparing to 0.0 TU with DM (82.81% in 0.1 TU, 56.14% in 1.0 TU and 44.68% in 2.0 TU) and with CdCl₂ (74.68% in 0.1 TU, 52.05% in 1.0 TU and 50.14% in 2.0 TU) showed an overall decrease with the increase of exposure concentrations. According to Self-Organizing Map (SOM), the AChE activities were characterized in relation with experimental conditions, showing an inverse relationship with exposure time. As the exposure time was longer, the AChE activities were correspondingly lower. The AChE inhibition showed time delay in sublethal treatments (0.1 TU) in different tissues: the AChE was first inhibited in brain by chemicals followed by gill, muscle and liver (brain > gill > muscle > liver). The AChE activity was almost inhibited synchronously in higher environmental stress (1.0 TU and 2.0 TU). As the AChE inhibition can induce abnormal of behavior movement, these results will be helpful to the mechanism of stepwise behavior responses according to the time difference in different tissues rather than the whole body AChE activity.

Daphniatox - Online monitoring of aquatic pollution and toxic substances

The microcrustacean Daphnia is sensitive to many toxic substances and can be cultured easily. The Daphniatox instrument is based on computerized image analysis tracking swimming organisms in real time. The software evaluates 14 endpoints including motility, swimming velocity, orientation with respect to light and gravity as well as cell form and size. The system determines movement vectors of a large number of organisms to warrant high statistical significance and calculates mean values as well as standard deviation. Tests with K dichromate show that the toxin inhibits motility (EC₅₀ 0.75 mg/L), swimming velocity (EC₅₀ 0.70 mg/L) and even causes a significant decrease in length (16% at 4 mg/L) and changes the form of the animals, This bioassay can be used to monitor the toxicity of a large number of dissolved pollutants and toxic substances such as arsenic, dichromate and persistent organic pollutants.

Behavior persistence in defining threshold switch in stepwise response of aquatic organisms exposed to toxic chemicals

As a characteristic in bacterial colony, persistence model described the dynamics of two subpopulations (normal (n) and persister (p)). In order to illustrate the switch of "Threshold" in the stepwise behavior responses of organisms, it is hypothesized that total behavior (B_t) of organisms consists of two types in behavior tendency, intoxication (B_p) and normal/recovery behavior (B_n). Both B_p and B_n could be concurrently affected by environmental stress E, and behavior response modes (M) are decided by the relationship between E and toxicity threshold of test organisms (T_i). The results suggested stress constant λ was decided by the constant rates g_nE,g_pE, a_n and a_p. Due to different stress constant λ, the behavior responses of indicators showed great difference in different M, which included 'safe mode' (M_s), 'acclimation mode' (M_ac), 'adjustment mode' (M_aj) and 'toxic effect' (M_te). Usually, B_t during M_s could maintain around 0.8, and M_te would happen once it is lower than 0.2. According to the relationship between B_t values and E changes in 7 M_ajs, behavior persistence relying on adjustment could reflect the behavior homeostasis of organisms under environmental stress and be regarded as a threshold switch for the stepwise behavior responses. The mathematical analysis of behavior persistence allows making a quantitative prediction on environment assessment that would promote the emergence of persistence, as well as evaluating its ecological implications.

Integrative Characterization of Toxic Response of Zebra Fish (Danio rerio) to Deltamethrin Based on AChE Activity and Behavior Strength

In order to characterize the toxic response of zebra fish (Danio rerio) to Deltamethrin (DM), behavior strength (BS) and muscle AChE activity of zebra fish were investigated. The results showed that the average values of both BS and AChE activity showed a similarly decreased tendency as DM concentration increased, which confirmed the dose-effect relationship, and high and low levels of AChE and BS partly matched low and high levels of exposure concentrations in self-organizing map. These indicated that AChE and BS had slight different aspects of toxicity although overall trend was similar. Behavior activity suggested a possibility of reviving circadian rhythm in test organisms after exposure to the chemical in lower concentration (0.1 TU). This type of rhythm disappeared in higher concentrations (1.0 TU and 2.0 TU). Time series trend analysis of BS and AChE showed an evident time delayed effect of AChE, and a 2 h AChE inhibition delay with higher correlation coefficients (r) in different treatments was observed. It was confirmed that muscle AChE inhibition of zebra fish is a factor for swimming behavior change, though there was a 2 h delay, and other factors should be investigated to illustrate the detailed behavior response mechanism.

Environmental and Ecological Risk Assessment of Trace Metal Contamination in Mangrove Ecosystems: A Case from Zhangjiangkou Mangrove National Nature Reserve, China

Zhangjiangkou Mangrove National Nature Reserve is a subtropical wetland ecosystem in southeast coast of China, which is of dense population and rapid development. The concentrations, sources, and pollution assessment of trace metals (Cu, Cd, Pb, Cr, Zn, As, and Hg) in surface sediment from 29 sites and the biota specimen were investigated for better ecological risk assessment and environmental management. The ranges of trace metals in mg/kg sediment were as follows: Cu (10.79–26.66), Cd (0.03–0.19), Pb (36.71–59.86), Cr (9.67–134.51), Zn (119.69–157.84), As (15.65–31.60), and Hg (0.00–0.08). The sequences of the bioaccumulation of studied metals are Zn > Cu > As > Cr > Pb > Cd > Hg with few exceptions. Cluster analysis and principal component analysis revealed that the trace metals in the studied area mainly derived from anthropogenic activities, such as industrial effluents, agricultural waste, and domestic sewage. Pollution load index and geoaccumulation index were calculated for trace metals in surface sediments, which indicated unpolluted status in general except Pb, Cr, and As.

Optimization of a Coastal Environmental Monitoring Network Based on the Kriging Method: A Case Study of Quanzhou Bay, China

Environmental monitoring is fundamental in assessing environmental quality and to fulfill protection and management measures with permit conditions. However, coastal environmental monitoring work faces many problems and challenges, including the fact that monitoring information cannot be linked up with evaluation, monitoring data cannot well reflect the current coastal environmental condition, and monitoring activities are limited by cost constraints. For these reasons, protection and management measures cannot be developed and implemented well by policy makers who intend to solve this issue. In this paper, Quanzhou Bay in southeastern China was selected as a case study; and the Kriging method and a geographic information system were employed to evaluate and optimize the existing monitoring network in a semienclosed bay. This study used coastal environmental monitoring data from 15 sites (including COD, DIN, and PO₄-P) to adequately analyze the water quality from 2009 to 2012 by applying the Trophic State Index. The monitoring network in Quanzhou Bay was evaluated and optimized, with the number of sites increased from 15 to 24, and the monitoring precision improved by 32.9%. The results demonstrated that the proposed advanced monitoring network optimization was appropriate for environmental monitoring in Quanzhou Bay. It might provide technical support for coastal management and pollutant reduction in similar areas.

Bacoside A and bromelain relieve dichlorvos induced changes in oxidative responses in mice serum

Reactive oxygen species (ROS) may be involved in the pathogenesis of serum induced by dichlorvos. Therefore, the rationale of present research was to evaluate the ameliorative efficacy of bacoside A and bromelain on oxidative stress biomarkers in serum of dichlorvos intoxicated mice. Also the level of serum antioxidants viz. catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and reduced glutathione (GSH) were measured. For experiments, mice were allocated into six groups. First group received saline as a vehicle; second group was administered with dichlorvos (40 mg/kg b.w.); third group was administered with bromelain (70 mg/kg b.w.), fourth group received dose of bacoside A (5 mg/kg b.w.), fifth group was given concomitant exposure of bacoside A and bromelain both and mice of sixth group were exposed to bacoside A, bromelain and dichlorvos for 21 days consecutively. Oxidative stress biomarkers thiobarbituric acid reactive substances (TBARS) and protein carbonyl content (PCC) and antioxidants (CAT, SOD, GPx and GSH) level of serum was determined to elucidate the protective potential of bacoside A and bromelain against dichlorvos intoxication. Significantly increased TBARS and PCC level in second group suggests that dichlorvos enhances the production of free radicals in serum of mice (p < 0.05). Antioxidants treatment significantly decreased the levels of TBARS and PCC (p < 0.05). Dichlorvos administration causes a significant reduction in the level of CAT, SOD, GPx and GSH (p < 0.05) which was restored significantly by co-administration of bromelain and bacoside A in dichlorvos exposed mice (p < 0.05). The bacoside A and bromelain are attributed with antioxidant properties. Finding of research conclude that concomitant exposure of bacoside A and bromelain was much effective in combating oxidative stress induced by dichlorvos.

The toxic effects of deltamethrin on Danio rerio: the correlation among behavior response, physiological damage and AChE

In this work we comprehensively evaluated the effects of deltamethrin, a pyrethroid pesticide, on the behavior, physiology and acetylcholinesterase (AChE) activity of fish.

Quercetin protects HCT116 cells from Dichlorvos-induced oxidative stress and apoptosis

The present study was designed to assess the possible protective effects of Quercetin (QUER), a flavonoid with well-known pharmacological effects, against Dichlorvos (DDVP)-induced toxicity in vitro using HCT116 cells. The cytotoxicity was monitored by cell viability, reactive oxygen species (ROS) generation, anti-oxidant enzyme activities, malondialdehyde (MDA) production, and DNA fragmentation. The apoptosis was assessed through the measurement of the mitochondrial transmembrane potential (ΔΨm) and caspase activation. The results indicated that pretreatment of HCT116 cells with QUER, 2 h prior to DDVP exposure, significantly decreased the DDVP-induced cell death, inhibited the ROS generation, modulated the activities of catalase (CAT) and superoxide dismutase (SOD), and reduced the MDA level. The reductions in mitochondrial membrane potential, DNA fragmentation, and caspase activation were also attenuated by QUER. These findings suggest that dietary QUER can protect HCT116 cells against DDVP-induced oxidative stress and apoptosis.