Zongming Ren

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

As a key enzyme that hydrolyzes the neurotransmitter acetylcholine in cholinergic synapses of both vertebrates and invertebrates, acetylcholinesterase (AChE) is strongly inhibited by organophosphates. AChE inhibition may induce the decrease of swimming ability. According to previous research, swimming behavior of different aquatic organisms could be affected by different chemicals, and there is a shortage of research on direct correlation analysis between swimming behavior and biochemical indicators. Therefore, swimming behavior and whole-body AChE activity of Daphnia magna under dichlorvos (DDVP) exposure were identified in order to clarify the relationship between behavioral responses and AChE inhibition in this study. In the beginning, AChE activity was similar in all treatments with the control. During all exposures, the tendency of AChE activity inhibition was the same as the behavioral responses of D. magna. The AChE activity of individuals without movement would decrease to about zero in several minutes. The correlation analysis between swimming behavior of D. magna and AChE activity showed that the stepwise behavioral response was mainly decided by AChE activity. All of these results suggested that the toxicity characteristics of DDVP as an inhibitor of AChE on the swimming behavior of organisms were the same, and the AChE activity inhibition could induce loss of the nerve conduction ability, causing hyperactivity, loss of coordination, convulsions, paralysis and other kinds of behavioral changes, which was illustrated by the stepwise behavioral responses under different environmental stresses.

Persistence Parameter: a Reliable Measurement for Behavioral Responses of Medaka (Oryzias latipes) to Environmental Stress

Online monitoring systems provided a significant evidence for feasibility of the stepwise behavioral response model in detecting the effects of organophosphorus pesticides on movements of medaka (Oryzias latipes), being able to determine the state of indicator organisms, “no effect,” “stimulation,” “acclimation,” “adjustment (readjustment),” and “toxic effect.” Though the stepwise behavioral response model postulated that an organism displays a time-dependent sequence of compensatory stepwise behavioral response during exposure to pollutants above their respective thresholds of resistance, it was still a conceptual model based on tendency only in analysis. In this study, the phenomenon of bacterial persistence was used to interpret the relationship between the stepwise behavioral response model and the environmental stress caused by both exposure time and different treatments. Quantitative measurements of the stepwise behavioral response model led to a simple mathematical description of the threshold switch, which evaluated the effects of environmental stress on behavioral responses to decide the tendency. The adjustment ability correlated to “persisters (p)” is very important for test individuals to overcome the “threshold” from the outside environmental stress. The computational modeling results suggested that “persister (p),” as described in the general equations of bacterial persistence model in changing environments, illustrated behavior acclimation and adjustment (or readjustment) clearly. Consequently, the persistence parameter, p, was critical in addressing for medaka to be adapted to fluctuating environments under different environmental stress.

Is sodium percarbonate a good choice in situ remediation of deltamethrin pollution

In this research, the toxic effects of deltamethrin (DM) on the behavior responses of Zebra fish (Danio rerio) in the characteristic of behavior strength were investigated followed by an assessment of an in situ remediation of the DMpollution using sodium percarbonate. Behavior strength of Danio rerio was approximately 0.83 in the control group and was slightly higher than 0.83 in the sublethal treatment (0.1 TU (toxic unit)), which suggested that sublethal DMexposure could induce a stimulation effect in 48 h of exposure. In lower DM concentration treatments (0.5 and 1.0 TU), behavior strength could be inhibited significantly. Behavior responses of Danio rerio showed a gradually increased tendency when they were exposed to higher concentration of DM, and the declining amplitudes of behavior strength changed with the increase of DMconcentrations. These results suggested that DM had evident acute toxicity effects on the behavior responses of Danio rerio with a good dose-effect relationship. The in situ remediation of the DM pollution using sodium percarbonate showed that the toxic effect of DM on behavior responses of Danio rerio could be eliminated even in the highest concentration of DM (5.0 TU). Meanwhile, the behavior response of Danio rerio in the treatment of sodium percarbonate was the same as in the control, which indicated that sodium percarbonate had no evident toxic effects on the behavior of Danio rerio in the current concentration. This study suggested that adding sodium percarbonate in situ might be a good way to eliminate the DM toxic effects.

The Stepwise Behavioral Responses: Behavioral Adjustment of the Chinese Rare Minnow (Gobiocypris rarus) in the Exposure of Carbamate Pesticides

In order to illustrate the behavioral regulation in environmental stress, the behavioral responses of the Chinese rare minnow (Gobiocypris rarus) to arprocarb, carbofuran, and oxamyl were analyzed with an online monitoring system. The Self-Organizing Map (SOM) was used to define the patterns of the behavioral data obtained from treatments at concentrations of 0.1 toxic unit (TU), 1 TU, 2 TU, 5 TU, 10 TU, and 20 TU and a control. In certain cases, differences among the carbamate pesticides (CPs) tested were observed. The profiles of behavioral strength (BS) in SOM varied according to the concentration used. The time of the first significant decrease of the BS varied inversely with the CP concentrations. The results suggested that the behavioral regulation in the stepwise behavioral responses (SBR) was evident. The primary movement behaviors shown by the SBR model included no effect, stimulation, acclimation, adjustment (readjustment), and toxic effect, especially at the lower concentrations. However, higher stress (10 TU and 20 TU) might limit the function of the behavioral adjustment produced by the intrinsic response mechanisms. It was concluded that SBR, which were affected by both the concentration and the exposure time, could be used as a suitable indicator in the ecotoxicological risk assessment of CPs.

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.

Environmental Characteristics of Polybrominated Diphenyl Ethers in Marine System, with Emphasis on Marine Organisms and Sediments

Polybrominated diphenyl ethers (PBDEs), due to their widespread usage as flame retardants and their lipophilicity and persistence, have become ubiquitous in the environment. It is urgent to understand the environmental characteristics of PBDEs in marine system, but they have attracted little attention. We summarize the available data and analyze the regional distributions, controlling factors, and congener patterns of PBDEs in marine and associated environmental matrixes worldwide. Based on meta-analysis, after separating the estuarial sites from the marine sites, ignoring the extraordinary sample sites such as those located just near the point source, the PBDE concentration levels are still in the same order of magnitude from global scale. Despite Principal Component Analysis, the congener patterns of sediments are predominant with the heavy brominated congeners (BDE-209 contributing over 75% to the total load) while the biota abound with the light ones (BDE-47, BDE-99, and BDE-100 taking about 80%). The ratio between BDE-99 and BDE-100 for the lower trophic-level species often turns to be greater than 1, while for those higher species the ratio may be below 1, and some species feed mainly on the crustaceans and zooplankton seems to have a higher ratio value. The data of the PBDEs in marine system are currently limited; thus, data gaps are identified as well.

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.

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.