The stepwise behavioral responses: behavioral adjustment of the Chinese rare minnow (Gobiocypris rarus) in the exposure of carbamate pesticides

Pesticide screening of surface water and soil along the Mekong River in Cambodia

Widespread use of pesticides globally has led to serious concerns about environmental contamination, particularly with regard to aquatic and soil ecosystems. This work involved investigating concentrations of 64 pesticides in surface-water and soil samples collected in four provinces along the Mekong River in Cambodia during the dry and rainy seasons (276 samples in total), and conducting semi-structured interviews with local farmers about pesticide use. Furthermore, an ecological risk assessment of the detected pesticides was performed. In total, 56 pesticides were detected in surface water and 43 in soil, with individual pesticides reaching maximum concentrations of 1300 ng/L in the surface-water samples (tebufenozide) and 1100 ng/g dry weight in the soil samples (bromophos-ethyl). The semi-structured interviews made it quite evident that the instructions that farmers are provided regarding the use of pesticides are rudimentary, and that overuse is common. The perceived effect of pesticides was seen as an end-point, and there was a limited process of optimally matching pesticides to pests and crops. Several pesticides were used regularly on the same crop, and the period between application and harvest varied. Risk analysis showed that bromophos-ethyl, dichlorvos, and iprobenfos presented a very high risk to aquatic organisms in both the dry and rainy seasons, with risk quotient values of 850 for both seasons, and of 67 in the dry season and 78 in the rainy season for bromophos-ethyl, and 49 in the dry season and 16 in the rainy season for dichlorvos. Overall, this work highlights the occurrence of pesticide residues in surface water and soil along the Mekong River in Cambodia, and emphasizes the urgent need for monitoring and improving pesticide practices and regulations in the region.

A critical review of effect modeling for ecological risk assessment of plant protection products

A wide diversity of plant protection products (PPP) is used for crop protection leading to the contamination of soil, water, and air, which can have ecotoxicological impacts on living organisms. It is inconceivable to study the effects of each compound on each species from each compartment, experimental studies being time consuming and cost prohibitive, and animal testing having to be avoided. Therefore, numerous models are developed to assess PPP ecotoxicological effects. Our objective was to provide an overview of the modeling approaches enabling the assessment of PPP effects (including biopesticides) on the biota. Six categories of models were inventoried: (Q)SAR, DR and TKTD, population, multi-species, landscape, and mixture models. They were developed for various species (terrestrial and aquatic vertebrates and invertebrates, primary producers, micro-organisms) belonging to diverse environmental compartments, to address different goals (e.g., species sensitivity or PPP bioaccumulation assessment, ecosystem services protection). Among them, mechanistic models are increasingly recognized by EFSA for PPP regulatory risk assessment but, to date, remain not considered in notified guidance documents. The strengths and limits of the reviewed models are discussed together with improvement avenues (multigenerational effects, multiple biotic and abiotic stressors). This review also underlines a lack of model testing by means of field data and of sensitivity and uncertainty analyses. Accurate and robust modeling of PPP effects and other stressors on living organisms, from their application in the field to their functional consequences on the ecosystems at different scales of time and space, would help going toward a more sustainable management of the environment. Graphical Abstract Combination of the keyword lists composing the first bibliographic query. Columns were joined together with the logical operator AND. All keyword lists are available in Supplementary Information at https://doi.org/10.5281/zenodo.5775038 (Larras et al. 2021).

Synthetic organic chemicals (flame retardants and pesticides) with neurotoxic potential induced behavioral impairment on zebrafish (Danio rerio): a non-invasive approach for neurotoxicology

Behavior responses of organisms can be used as a non-invasive method for neurotoxicology studies since it directly links the nervous system's functioning and biochemical activities. Among different behavioral activities, aquatic organisms' swimming behavior (fitness) is the essential factor for health assessment; thus, it is practiced routinely in neurotoxicological studies. Zebrafish (Danio rerio) are excellent models for neurotoxicology studies. Based on the above information, we hypothesized that zebrafish's swimming behavior is a potential biomarker for neurotoxic effect assessment. We exposed zebrafish (length, 3-4 cm; weight, 0.2-0.3 g) to different synthetic organic chemicals (organophosphorus flame retardants (tri-cresyl phosphate and cresyl diphenyl phosphate) and neurotoxic pesticides (cypermethrin and methomyl) for 15 days. For each test chemical, we chose two different concentrations (Treatment-I 5 μL/L and Treatment-II 25 μL/L) to study their eco-toxicity. The swimming strength of zebrafish was quantified using an online monitoring system. The swimming strength of zebrafish decreased under different treatments (Treatment-I (5 μL/L) and -II (25 μL/L)) of target chemicals. The circadian rhythm of zebrafish was predominantly not affected in this study. Higher neurotoxic effect (behavioral impairment) was observed in Treatment-II when compare to Treatment-I of organophosphorus flame retardants and pesticides groups. Responses of zebrafish under organophosphorus flame retardant (tri-cresyl phosphate and cresyl diphenyl phosphate) treatments were identical with pesticide (cypermethrin and methomyl) treatments. Based on the results, we conclude that swimming behavior could be an ideal non-invasive biomarker to assess waterborne contaminants' neurotoxic effect.

Chemicals affect color preference in rare minnow (Gobiocypris rarus)

Behavioral response of fish has been shown that was sensitive to chemicals in water. Herein, larval and adult rare minnows of Gobiocypris rarus were studied for their innate color preference and response to a concentration gradient of chemicals (cadmium ion [Cd²⁺], tricaine methanesulfonate [MS222], and p-chloroaniline). The results showed that both larval and adult rare minnows preferred blue and green over yellow and red in water with no chemicals added. Larval color preference changed significantly under concentrations of Cd²⁺ ≥ 0.4 mg/L, MS222 ≥ 3 mg/L, and p-chloroaniline ≥ 10 mg/L; for adults, color preference changed significantly when Cd²⁺ ≥ 3 mg/L, MS222 ≥ 34 mg/L, and p-chloroaniline ≥ 38 mg/L. In addition, the color preference priorities of both larvae and adults also changed at high concentrations of chemicals. The present study provides useful information on how changes in rare minnow behavior could be used as an early indicator of water pollution.

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.

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.