Acute Atrazine Exposure has Lasting Effects on Chemosensory Responses to Food Odors in Crayfish (Orconectes virilis)

Early and transitory hypoactivity and olfactory alterations after chronic atrazine exposure in female Sprague-Dawley rats

Several studies have shown that chronic exposure to the herbicide atrazine (ATR) causes alterations in locomotor activity and markers of the dopaminergic systems of male rats. However, few studies have evaluated the sex-dependent effects of atrazine exposure. The aim of the present study was to evaluate whether chronic ATR exposure causes alterations in behavioral performance and dopaminergic systems of female rats. At weaning, two groups of rats were exposed to 1 or 10 mg ATR/kg body weight daily thorough the food, while the control group received food without ATR for 14 months. Spontaneous locomotor activity was evaluated monthly for 12 months, while anxiety, egocentric and spatial memory, motor coordination, and olfactory function tasks were evaluated between 13 and 14 months of ATR exposure. Tyrosine hydroxylase (TH) and monoamine content in brain tissue were assessed at the end of ATR treatment. Female rats treated with 1 or 10 mg ATR showed vertical hypoactivity compared to the control group only in the first month of ATR exposure. Impairments in olfactory functions were found due to ATR exposure. Nevertheless, no alterations in anxiety, spatial and egocentric memory, or motor coordination tasks were observed, while the levels of TH and dopamine and its metabolites in brain tissue were similar among groups. These results suggest that female rats could present greater sensitivity to the neurotoxic effects of ATR on spontaneous locomotor activity in the early stages of development. However, they are unaffected by chronic ATR exposure later in life compared to male rats. More studies are necessary to unravel the sex-related differences observed after chronic ATR exposure.

Ecological Toxicity of Cyantraniliprole against Procambarus clarkii: Histopathology, Oxidative Stress, and Intestinal Microbiota

Cyantraniliprole is a novel insecticide recently introduced for rice pest control that may cause potential threats to the red swamp crayfish (Procambarus clarkii) in rice-crayfish coculture systems. In this study, we investigated the acute toxicity of cyantraniliprole against P. clarkii with a LC50 value of 149.77 mg/L (96 h), first. Some abnormal behaviors of P. clarkii treated with 125 mg/L cyantraniliprole, including incunabular hyperexcitability, imbalance, inactivity, and increased excretion were observed. Moreover, it was observed that exposure to 5 mg/L cyantraniliprole for 14 days resulted in histopathological alterations in abdominal muscle, gills, hepatopancreas, and intestines. Furthermore, exposure to 0.05 and 5 mg/L cyantraniliprole induced increased activities of several oxidative stress-related enzymes, which was verified by the upregulation of related genes. Additionally, dysregulation of the intestinal microbiota was determined via 16S rRNA sequencing. These results will provide the basis for the utilization of cyantraniliprole in the fields of rice-crayfish integrated system.

The combined effects of atrazine and warming on environmental adaptability in lizards (Eremias argus) from the perspective of a life-history traits trade-off: Gender differences in trade-off strategies may reverse mortality risk

Life-history theory suggests that organisms must distribute a limited share of their energetic resources among competing life-history trait demands. Therefore, the trade-off strategies individuals develop for particular life-history traits in a given environment may profoundly impact their environmental adaptability. In this study, lizards (Eremias. argus) were exposed to single and combined atrazine (4.0 mg·kg^-1 and 20.0 mg·kg^-1) and different temperatures (25 °C and 30 °C) for 8 weeks during the breeding season. The effects of atrazine and warming on the adaptability of lizards were explored by examining changes in trade-offs via several key life history traits (i.e., reproduction, self-maintenance, energy reserves, and locomotion). The results show that after atrazine exposure at 25 °C, both female and male lizards tended to allocate energy to self-maintenance by reducing energy allocation to reproductive process. The lower energy reserves of males are considered a "risky" life-history strategy and the observed higher mortality may be related to atrazine-induced oxidative damage. The retention of energy reserves by females not only ensured their current survival but also facilitated survival and reproduction in subsequent stages, which can be regarded as a "conservative" strategy. However, under high temperature and/or combined atrazine exposure, the "risky" strategy of males caused them to consume more energy reserves to invest in self-maintenance, which ensured their immediate survival, and profited from more rapid degradation of atrazine. In contrast, the "conservative" strategy of females could not meet their higher reproductive and self-maintenance demands under high temperatures, and the elevated reproductive oxidative and metabolic costs led to individual mortality. Gender differences in life-history trade-off strategies can directly lead to "winners" and "losers" from environmental stress within a species.

Environmentally relevant atrazine exposure leads to increases in DNA damage and changes in morphology in the hepatopancreas of crayfish (Faxonius virilis)

The herbicide atrazine is widely used for controlling broad leaf weeds and increasing crop yields in agricultural areas. Atrazine enters aquatic environments through runoff, ground water discharge and seepage where concentrations have been recorded above 300 ppb. Exposure to the herbicide atrazine at environmentally relevant concentrations has been shown to negatively impact aquatic organisms, including crayfish. Because xenobiotics are concentrated in the crayfish hepatopancreas (digestive gland), we examined changes in morphology and DNA damage in hepatopancreatic tissue structure and cells following a 10-day exposure to atrazine (0, 10, 40, 80, 100 and 300 ppb). We found that there were marked morphological changes, post-exposure, for all atrazine concentrations tested. Hepatopancreatic tissue exhibited degenerated tubule epithelium with necrosis of microvilli, tubule lumen dilation, changes in tubular epithelium height and vacuolization of the epithelium. Likewise, we also performed a terminal deoxynucleotidyl transferase (TdT) mediated dUTP nick-end labeling (TUNEL) assay which showed the percentage of cells with DNA damage increased following atrazine exposure. Crayfish hepatopancreatic tissue displayed significant increases in TUNEL-positive cells following exposure to atrazine at 100 ppb and above. Overall, exposure to atrazine at environmentally relevant concentrations damages hepatopancreatic tissue. This impairment could lead to changes in biotransformation, detoxification, digestion and molting, subsequently reducing crayfish populations and negatively impacting the aquatic ecosystem.

Clothianidin interferes with recognition of a previous encounter in rusty crayfish (Faxonius rusticus) due to a chemosensory impairment

Clothianidin, a neonicotinoid insecticide that binds to arthropod nicotinic acetylcholine receptors, is widely used to protect plants against a wide variety of agricultural pests. Little is known about how this insecticide affects non-target invertebrate species in aquatic environments. In this study, we explored the effects of aqueous exposures of clothianidin on locomotion, chemosensory-based responses, and agonistic encounters of rusty crayfish (Faxonius rusticus). Clothianidin exposures at a concentration of 1.0 μg/L (i.e., 1.0 ppb) did not alter initiations and retreats, but did increase the amount of time the crayfish interacted per interaction. In a subsequent food cue experiment with crayfish exposed to clothianidin concentrations of 0.4 μg/L and 1.0 μg/L, the test organisms demonstrated chemosensory dysfunction, but no decrease in locomotory movement. As chemosensation is essential for recognizing previous rivals in crayfish, the loss of this sense likely resulted in the exposed crayfish being unable to detect cues used to recognize a previous competitor. An inability to recognize a previous competitor (and who won or lost the previous interaction) could result in crayfish spending more time fighting and less time on foraging and reproduction. This study demonstrates that exposures of crayfish to clothianidin at concentrations found in the environment affects the behavioural ecology of these aquatic invertebrates.

Comprehensive fitness evaluation of common carp (Cyprinus carpio L.) after twelve weeks of atrazine exposure

Atrazine is frequently detected in surface waters and negatively affect physiological function in aquatic organisms. Even though numerous authors have intensively studied its toxicity, only limited information concerning the long-term fish exposure is available. The aim of this study was evaluation of chronic exposure in common carp. Fish were exposed to a range of atrazine concentrations (0.3 - environmentally relevant concentration; 300; 1000; and 3000 µg/l) for twelve weeks. The potential impact of atrazine exposure was studied using various markers (behaviour; biometrical characteristics; haematological, biochemical and oxidative stress indices and histopathological changes). Most alterations were recorded at the highest concentration (3000 µg/l) which is probably due to a combined effect of both the herbicide exposure and intensive parasite infection development during second week. This group was cancelled after three weeks due to adverse health status, which partly confirmed atrazine immunotoxicity. Chronic exposure resulted in long-term reduction in feed intake followed by a significant decrease in body weight and morphological changes in gill at 1000 µg/l. At the same concentration, significant alterations in haematological (e.g. increase in erythrocyte, leukocyte, lymphocytes and neutrophil counts as well as decrease in monocyte counts) and biochemical (e.g. changes in enzyme activities; increase in glucose; decrease in ammonia) indices were documented, especially during first three weeks. Similar trend, but not so intensive, was observed at 300 µg/l. Moreover, significant changes were observed in various indicators of oxidative stress. These alterations were highly variable with both increasing and decreasing trends depending on dose and analysed tissue. Significant changes, especially in white blood profile, enzyme activities and oxidative stress indices, were proven even at 0.3 µg/l. Obtained results indicate that chronic atrazine exposure of common carp can negatively influence many indicators of health status such as behaviour, immune response, haematological and biochemical profile, oxidative stress indices and organ histopathology.

Environmentally relevant atrazine exposures cause DNA damage in cells of the lateral antennules of crayfish (Faxonius virilis)

The herbicide atrazine is heavily applied in agricultural areas in the Midwestern United States and can run-off and seep into surrounding aquatic habitats where concentrations can reach over 300 ppb. It is known that acute exposures to 80 ppb atrazine cause lasting deficiencies in the chemoreception of food and mate odors. Since atrazine impairs chemosensory responses, the goal of this study was to determine the effect of atrazine on cells, including olfactory sensory neurons, located in the lateral antennules of crayfish. In this experiment, we treated crayfish for 10 days with ecologically relevant concentrations of 0, 10, 40, 80, 100 and 300 ppb (μg L^-1) of atrazine. Following treatments, the distal portion of the lateral antennules was cryosectioned. We used a TdT mediated dUTP nick-end labeling (TUNEL) assay to determine if any cells had DNA damage and may be thus undergoing apoptosis. We found that as atrazine concentrations increase above 10 ppb, the number of TUNEL-positive cells, visualized in the lateral antennules, significantly increases. Our data show that atrazine exposure causes DNA damage in cells of the lateral antennules, including olfactory sensory neurons, thus leading to impairments in chemosensory abilities. Because crayfish rely heavily on chemoreception for survival, changes in their ability to perceive odors following atrazine exposure may have detrimental effects on population size.

Cytochrome P450 and Glutathione-S-Transferase Activity are Altered Following Environmentally Relevant Atrazine Exposures in Crayfish (Faxoniusvirilis)

The herbicide atrazine is heavily applied in the U.S. Midwest to control broadleaf weeds. It enters local streams and rivers through runoff and seepage, and exposure can affect non-target aquatic organisms, like crayfish. We examined sublethal effects of atrazine on the expression and activity of the detoxification enzymes cytochrome P450 (CYP450) and glutathione-S-transferase (GST) in crayfish. Crayfish were exposed to 0, 10, 40, 80, 100 and 300 ppb atrazine for 1, 2, 4, 7 and 10 days. Their hepatopancreas was collected and CYP450 expression and GST activity was analyzed. Atrazine exposure caused differential expression and activity of CYP450 and GST. CYP450 expression varied over exposure concentrations and time. Further, GST activity significantly increased following a 2 day, 10 ppb exposure to atrazine and a 300 ppb atrazine exposure for all days tested. We found that atrazine detoxification is a dynamic process that changes with the length and intensity of atrazine exposure.

Express yourself: Individuals with bold personalities exhibit increased behavioral sensitivity to dynamic herbicide exposure

The majority of ecotoxicological studies performed measure average responses from individuals which do not account for the inter-individual variation in the responses of animals to environmental stimuli (i.e. the personality of individuals). Thus, these designs assume that all individuals will respond to contaminant exposure in a similar manner. Additionally, commonly used constant, static exposure regime designs neglect to recognize the spatial and temporal variation in contaminant plume structures as they move throughout fluid environments. The purpose of this study was to understand the effects of the structural characteristics (concentration, duration, and frequency) of temporally and spatially variant contaminant plumes on the personality of individuals. This experimental design aimed to construct a sensitive definition of exposure by connecting sublethal effects of toxicants and realistic exposure regimes. This study used escape response of Faxonius virilis crayfish from the predatory odor of Micropterus salmoides prior to and following exposure to the herbicide, atrazine. Atrazine was delivered in pulses to flow through exposure arenas for a total of 47 h while manipulating the concentration, frequency, and duration of the herbicide pulses. Escape response of crayfish prior to exposure was used to categorize animals into bold and shy personalities. The change in escape response was analyzed and resulted in a personality-dependent behavioral sensitivity to the polluted environment. Individuals classified as bold showed increased change in response to predatory odor relative to shy animals. Bold animals exhibited decreased activity after exposure where no change was presented in shy individuals. Shifts in individual behavior have impacts on the population level (e.g. resource acquisition/value; interspecies competition) and the ecosystem level (e.g. food web dynamics; trophic cascades). This study demonstrates the importance of sensitive measures in ecological risk assessment methods.

Effects of atrazine on life parameters, oxidative stress, and ecdysteroid biosynthetic pathway in the marine copepod Tigriopus japonicus

Atrazine is a widely used pesticide which acts as an endocrine disruptor in various organisms. The aim of this study was to investigate adverse effects of atrazine on life parameters, oxidative stress, and ecdysteroid biosynthetic pathway in the marine copepod Tigriopus japonicus. In T. japonicus, no mortality was shown in response to atrazine up to 20 mg/L in acute toxicity assessment. In nauplii, retardation in the growth and prolonged molting and metamorphosis resulted under chronic exposure of atrazine at 20 mg/L. In addition, body sizes of T. japonicus nauplii were significantly decreased (P < 0.01 in length and P < 0.001 in width) in response to 20 mg/L of atrazine. Furthermore, atrazine induced oxidative stress by the generation of reactive oxygen species at all concentrations compared to the control in the nauplii. Also, significant increase in glutathione-S transferase activity was observed in adult T. japonicus at low concentration of atrazine. To understand effects of atrazine on ecdysteroid biosynthetic pathway-involved genes (e.g., neverland, CYP307E1, CYP306A1, CYP302A1, CYP3022A1 [CYP315A1], CYP314A1, and CYP18D1) were examined with mRNA expressions of ecdysone receptor (EcR) and ultraspiracle (USP) in response to 20 mg/L atrazine in nauplii and adults. In the nauplii, these genes were significantly downregulated (P < 0.05) in response to atrazine, compared to the control but not in the adult T. japonicus. These results suggest that atrazine can interfere in vivo life parameters by oxidative stress-induced retrogression and ecdysteroid biosynthetic pathway in this species.

Exposure Through Runoff and Ground Water Contamination Differentially Impact Behavior and Physiology of Crustaceans in Fluvial Systems

Chemical pollutants enter aquatic systems through numerous pathways (e.g., surface runoff and ground water contamination), thus associating these contaminant sources with varying hydrodynamic environments. The hydrodynamic environment shapes the temporal and spatial distribution of chemical contaminants through turbulent mixing. The differential dispersal of contaminants is not commonly addressed in ecotoxicological studies and may have varying implications for organism health. The purpose of this study is to understand how differing routes of exposure to atrazine alter social behaviors and physiological responses of aquatic organisms. This study used agonistic encounters in crayfish Orconectes virilis as a behavioral assay to investigate impact of sublethal concentrations of atrazine (0, 40, 80, and 160 µg/L) delivered by methods mimicking ground water and surface runoff influx into flow-through exposure arenas for a total of 23 h. Each experimental animal participated in a dyadic fight trial with an unexposed opponent. Fight duration and intensity were analyzed. Experimental crayfish hepatopancreas and abdominal muscle tissue samples were analyzed for cytochrome P450 and acetylcholinesterase levels to discern mechanism of detoxification and mode of action of atrazine. Atrazine delivered via runoff decreased crayfish overall fight intensity and contrastingly ground water delivery increased overall fight intensity. The behavioral differences were mirrored by increases in cytochrome P450 activity, whereas no differences were found in acetylcholinesterase activity. This study demonstrates that method of delivery into fluvial systems has differential effects on both behavior and physiology of organisms and emphasizes the need for the consideration of delivery pathway in ecotoxicological studies and water-impairment standards.

Atrazine-xenobiotic nuclear receptor interactions induce cardiac inflammation and endoplasmic reticulum stress in quail (Coturnix coturnix coturnix)

Atrazine (ATR) is one of the most extensively used herbicide that eventually leaches into groundwater and surface water from agricultural areas. Exposure to ATR does harm to the health of human and animals, especially the heart. However, ATR exposure caused cardiotoxicity in bird remains unclear. To evaluate ATR-exerted potential cardiotoxicity in heart, quail were exposed with 0, 50, 250, and 500 mg/kg BW/day ATR by gavage treatment for 45 days. Cardiac histopathological alternation was observed in ATR-induced quail. ATR exposure increased the Cytochrome P450s and Cytochrome b5 contents, Cytochrome P450 (CYP) enzyme system (APND, ERND, AH, and NCR) activities and the expression of CYP isoforms (CYP1B1, CYP2C18, CYP2D6, CYP3A4, CYP3A7, and CYP4B1) in quail heart. The expression of nuclear xenobiotic receptors (NXRs) was also influenced in the heart by ATR exposure. ATR exposure significantly caused the up-regulation of pro-inflammatory cytokines (TNF-α, IL-6, NF-κB, and IL-8), down-regulation of anti-inflammatory cytokines (IL-10) expression levels and increased NO content and iNOS activity. The present research provides new insights into the mechanism that ATR-induced cardiotoxicity through up-regulating the expression levels of GRP78 and XBP-1s, triggering ER stress, activating the expression of IRE1α/TRAF2/NF-κB signaling pathway related factors (IRE1α, TRAF2, IKK, and NF-κB) and inducing an inflammatory response in quail hearts. In conclusion, ATR exposure could induce cardiac inflammatory injury via activating NXRs responses, disrupting CYP homeostasis and CYP isoforms transcription, altering NO metabolism and triggering ER stress and inflammatory response by activating IRE1α/TRAF2/NF-κB signaling pathway.

Lethal and Sublethal Effects of the Herbicide Atrazine in the Early Stages of Development of Physalaemus gracilis (Anura: Leptodactylidae)

Water sources used as reproductive sites by crying frog, Physalaemus gracilis, are extensively associated with agroecosystems in which the herbicide atrazine is employed. To evaluate the lethal and sublethal effects of atrazine commercial formulation, acute and chronic toxicity tests were performed in the embryonic phase and the beginning of the larval phase of P. gracilis. Tests were started on stage 19 of Gosner (Herpetologica 16:183-190, 1960) and performed in 24-well cell culture plates. Acute tests had a duration of 96 h with embryo mortality monitoring every 24 h. Chronic assays contemplated the transition from the embryonic to larval stages and lasted 168 h. Every 24 h the embryos/larvae were observed for mortality, mobility, and malformations. The LC50 of atrazine determined for P. gracilis embryos was 229.34 mg L^-1. The sublethal concentrations did not affect the development of the larvae but were observed effects on mobility and malformations, such as spasmodic contractions, reduced mobility, malformations in mouth and intestine, and edema arising. From 1 mg L^-1 atrazine, the exposed larvae began to have changes in mobility and malformations. The atrazine commercial formulation has caused early life effects of P. gracilis that may compromise the survival of this species but at higher concentrations than recorded in the environment, so P. gracilis can be considered tolerant to this herbicide at environmentally relevant concentrations.

Orexin receptor expression is increased during mancozeb-induced feeding impairments and neurodegenerative events in a marine fish

Food intake ensures energy resources sufficient for basic metabolism, immune system and reproductive investment. It is already known that food-seeking performances, which are crucially controlled by orexins (ORXs), may be under the influence of environmental factors including pollutants. Among these, mancozeb (mz) is becoming an environmental risk for neurodegenerative diseases. Due to few studies on marine fish exposed to mz, it was our intention to correlate feeding latency, food intake and feeding duration to potential neurodegenerative processes in key diencephalic sites and expression changes of the ORX neuroreceptor (ORXR) in the ornate wrasses (Thalassoma pavo). Hence, fish exposed for 4 days (d) to mz 0.2 mg/l (deriving from a 0.07, 0.14, 0.2, 0.3 mg/l screening test) displayed a significant reduction (p < 0.05) of food intake compared to controls as early as 1d that became more evident (p < 0.01) after 3d. Moreover, significant enhancements of feeding latency were reported after 1d up to 3d (p < 0.001) and even feeding duration was enhanced up to 3d (p < 0.001), which instead moderately increased after 4d (p < 0.05). A reduction (-120%; p < 0.001) of mean body weight was also detected at the end of exposure. Likewise, a notable (p < 0.001) activation of ORXR protein occurred together with mRNA up-regulations in diencephalic areas such as the diffuse nucleus of the inferior lobe (+48%) that also exhibited evident degenerative neuronal fields. Overall, these results highlight an ORX role as a vital component of the neuroprotective program under environmental conditions that interfere with feeding behaviors.

Exposure to Sublethal Ammonia Concentrations Alters the Duration and Intensity of Agonistic Interactions in the Crayfish, Orconectes rusticus

Crayfish extract information from chemical stimuli during social interactions. Commercial fertilizers increase background ammonia concentrations which may interfere with chemical communication. Background pollution can disrupt perception of chemical stimuli in three ways: masking, sensory impairment, physiological impairment or in combination. We investigated whether exposure to ammonia alters agonistic behavior. Crayfish pairs exposed to 0.9 mg/L ammonia fought for a longer duration, while crayfish exposed to 9.0 mg/L ammonia fought for a shorter duration. Altering activity patterns of crayfish may alter crayfish populations leading to a nonproportional impact because of their importance to the structure and function of aquatic ecosystems.

Diminished Conspecific Odor Recognition in the Rusty Crayfish (Orconectes rusticus) Following a 96-h Exposure to Atrazine

The presence of agricultural contaminants has been shown to disrupt olfactory-mediated behaviors in aquatic animals. We assessed the effects of atrazine on the ability of reproductively active (form I), male crayfish (Orconectes rusticus) to identify and respond to conspecific chemical signals involved in mating. Male crayfish were exposed to atrazine (80 ppb) and water (control) for 96 h. We analyzed odor localization and locomotor behaviors of herbicide-treated and control male crayfish to two different odor sources: female odor or water (control) delivered from the proximal end of a test arena. Control crayfish spent more time in the proximal region of the test arena and at the odor source. Atrazine-exposed crayfish showed no preference for the proximal region of the test arena and odor source when female odor was delivered. Atrazine exposure did not affect locomotor behaviors. Overall, atrazine-mediated chemosensory deficits have the potential to disrupt mating and affect population size.

Immunotoxic effects of atrazine and its main metabolites at environmental relevant concentrations on larval zebrafish (Danio rerio)

Atrazine (ATZ) and its main metabolites, i.e., diaminochlorotriazine (DACT), deisopropylatrazine (DIP), and deethylatrazine (DE), have been widely detected in surface water around the world. In the present study, to determine their immunotoxic effects, zebrafish during the early developmental stage were exposed to ATZ and its main metabolites at environmental concentrations (30, 100, 300 μg L^-1). It was observed that ATZ, DACT, DIP and DE selectively induced the transcription of immunotoxic related genes including Tnfα, Il-1β, Il-6, Il-8, Cxcl-clc and Cc-chem in larval zebrafish. Pretreatment with ATZ and its metabolites also changed the immune response of larval zebrafish to LPS and E. coli challenge, which was indicated by the alternation in the mRNA levels of some cytokines. In addition, 300 μg L^-1 ATZ and DACT exposure could also increase the release of tryptase into water, indicating that they increased the anaphylactoid reaction in the larval zebrafish. According to these results, both of ATZ and its metabolites exposure could cause the immunotoxicity in larval zebrafish. Thus, we thought that the ecological risks of the metabolites of ATZ on aquatic organisms could not be ignored.