Decreased Swimming Activity Research Articles

Tri-iso-butyl phosphate (TiBP) exposure induces neurotoxicity by triggering oxidative stress accompanied by neurotransmitter system disruptions and apoptosis in zebrafish larvae

The current research sheds light on the biological toxicity of organophosphate flame retardants (OPFRs), yet it overlooks the neurotoxicity and potential molecular mechanisms of tris(1,3-dichloro-2-propyl) phosphate (TiBP), a prominent constituent of the OPFRs. To address this, we utilized zebrafish larvae as a model to investigate TiBP's acute toxicity and neurotoxic effects, along with the associated molecular pathways. Our findings revealed that the 96 h and 120 h LC50 values for TiBP were 56.51 mg/L and 48.85 mg/L, respectively. Gradient exposure based on the 120 h LC50 demonstrated that TiBP induced developmental toxicity, characterized by elevated heart rate, reduced body length, and diminished eye distance. Additionally, a decrease in swimming activity was observed in the light test, along with the inhibition of the neuro crest cell development in Tg (HuC:eGFP) and Tg (sox10: eGFP) zebrafish larvae following TiBP exposure, as well as the alterations of neurogenesis and ACh-related genes. Expression of key neurodevelopment genes, including mbpa, gap43, nestin, ngfra, was significantly downregulated. Furthermore, heightened anxiety-like behaviors in open field and phototaxis tests were observed, concomitant with neurotransmitter imbalances. Specifically, there was an increase in DA levels, a decrease in GABA, and an upregulation of AChE activity. These disruptions were primarily mediated through transcriptional dysregulation of neurotransmitter synthesis, transport, and reception. Upon exposure to TiBP, zebrafish larvae exhibited a concentration-dependent increase in both ROS level and apoptosis. An upregulation of antioxidant enzymes and their transcription levels indicated the presence of oxidative stress in the larvae. The induction of ddit3 was congruent with the observed apoptosis, suggesting that it may be triggered by oxidative stress via the ERs-CHOP pathway. In summary, our study indicates that oxidative stress is a pivotal molecular event in the neurotoxicity induced by TiBP, implicating the disruption of the GABAergic, dopaminergic, and cholinergic systems, as well as triggering apoptosis.

Effects of Metabolic Disruption on Lipid Metabolism and Yolk Retention in Zebrafish Embryos.

A subgroup of endocrine-disrupting chemicals have the ability to disrupt metabolism. These metabolism-disrupting chemicals (MDCs) can end up in aquatic environments and lead to adverse outcomes in fish. Although molecular and physiological effects of MDCs have been studied in adult fish, few studies have investigated the consequences of metabolic disruption in fish during the earliest life stages. To investigate the processes affected by metabolic disruption, zebrafish embryos were exposed to peroxisome proliferator-activated receptor gamma (PPARγ) agonist rosiglitazone, the PPARγ antagonist T0070907, and the well-known environmentally relevant MDC bisphenol A. Decreased apolipoprotein Ea transcript levels indicated disrupted lipid transport, which was likely related to the observed dose-dependent increases in yolk size across all compounds. Increased yolk size and decreased swimming activity indicate decreased energy usage, which could lead to adverse outcomes because the availability of energy reserves is essential for embryo survival and growth. Exposure to T0070907 resulted in a darkened yolk. This was likely related to reduced transcript levels of genes involved in lipid transport and fatty acid oxidation, a combination of responses that was specific to exposure to this compound, possibly leading to lipid accumulation and cell death in the yolk. Paraoxonase 1 (Pon1) transcript levels were increased by rosiglitazone and T0070907, but this was not reflected in PON1 enzyme activities. The present study shows how exposure to MDCs can influence biochemical and molecular processes involved in early lipid metabolism and may lead to adverse outcomes in the earliest life stages of fish. Environ Toxicol Chem 2024;43:1880-1893. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effects of handling and surgical implant on juvenile wild trout: Physiological and behavioral impact.

Fish involved in telemetry studies are usually handled, anaesthetized, and subjected to internal tag implantation, all of which have the potential to disrupt the fish's physiology, migratory patterns, food-seeking behavior, growth, and survival. As fish tagging is a widespread standard method in aquaculture, it is crucial to gain a better understanding of the short- and long-term effects on various aspects of fish welfare. The experimental outcomes of each phase of the surgical process and how it affects the fish's ability to recover during the post-tagging period, particularly in small salmonids, are poorly understood. Thus, it is essential to measure the extent of these adverse effects to precisely extrapolate differences in surgical intervention for tagged fish compared to their unmanipulated counterparts. In our study, we explored the post-tagging impacts on wild-captured brown trout (Salmo trutta) (1+) juveniles. We examined the time effect on fish recovery after each phase of the surgical procedure, which included anaesthetized fish, followed by surgery with/without internal tagging, within the first 2 and 25 h post-surgery. Common blood parameters (glucose levels and haematocrit) and endpoints related to swimming behavior, including fish movement, direction, and social distancing aspects, were studied. The findings of the study indicated no significant changes in glucose and haematocrit levels over the observational period. Fish subjected to anesthesia and tagging procedures exhibited a significant decrease in swimming activity, recovering to baseline levels 1 h after anesthesia and 24 h after surgical (tagging) procedures in recirculating aquaculture systems. Tagged fish showed less social proximity than non-tagged fish in the first 2 h post-surgery. A significant effect size was observed between nonsurgical (anesthesia) and surgical (non-tagged/tagged) groups, highlighting a more pronounced impact associated with surgical tag interventions. Our data indicate that the magnitude of behavioral response was significantly influenced by tag weight (~1.4% body/tag weight ratio in water) among manipulated fish groups. Consequently, our study reveals that wild-captured S. trutta juveniles, tagged with commercially available low-weight acoustic tags (V6, 69 kHz), experienced negative effects on swimming performance. In surgical studies, acknowledging potential influences is crucial for accurately inferring fish physiological and behavioral status. Emphasizing fish recovery potential in both short- and long-term periods is essential for quantifying tagging effects. Future research should prioritize exploring alternative tagging technologies and refining methodologies, with a particular focus on assessing telemetry's impact on socioeconomically relevant small salmonids.

The effect of fishing-capture stress on the oxygen uptake rate and swimming activity of the holocephalan Callorhinchus milii.

Overfishing, capture mortality, and consequences following the release of surviving animals represent severe threats to chondrichthyans. Although holocephalans are common bycaught and discarded species, other than postrelease mortality, little is known of fishing capture stress impacts. The stress response elicited after capture, essential to increase survival chances, is energetically demanding and affects the amount of energy available for other biological activities, with potential long-term impairments. We measured the effect of 30-min simulated gillnet capture on oxygen uptake rate (ṀO2 ), a proxy for metabolic rate and energy use, on recovery pattern, and on swimming activity of elephant fish (Callorhinchus milii). Immediately after simulated capture, Active and Inactive ṀO2 , measured during swimming and resting periods, respectively, were 27.5% and 43.1% lower than precapture values. This metabolic decline is likely an adaptation for reducing the energy allocated to non-essential activities, thus preserving it to sustain the stress response and processes essential for immediate survival. Supporting this, after gillnet capture, animals decreased their swimming time by 26.6%, probably due to a reduction in the energy allocated to movement. After 7 days, swimming activity and both Inactive ṀO2 and Active ṀO2 returned to precapture values. Although metabolic decline may enhance survival chances, the associated decreased swimming activity might increase predation risk and slow the physiological recovery after a fishing event. Moreover, some of the activities involved in Inactive ṀO2 are fundamental for life maintenance and therefore its depression after a capture event might have long-term repercussions for life sustenance and health.

Long-term tralopyril exposure results in endocrinological and transgenerational toxicity: A two-generation study of marine medaka (Oryzias melastigma)

This study aims to investigate the impact of tralopyril, a newly developed marine antifouling agent, on the reproductive endocrine system and developmental toxicity of offspring in marine medaka. The results revealed that exposure to tralopyril (0, 1, 20 μg/L) for 42 days resulted in decreased reproductive capacity in marine medaka. Moreover, it disrupted the levels of sex hormones E2 and T, as well as the transcription levels of genes related to the HPG axis, such as cyp19b and star. Sex-dependent differences were observed, with females experiencing more pronounced effects. Furthermore, intergenerational toxicity was observed in F1 offspring, including increased heart rate, changes in retinal morphology and cartilage structure, decreased swimming activity, and downregulation of transcription levels of relevant genes (HPT axis, GH/IGF axis, cox, bmp4, bmp2, runx2, etc.). Notably, the disruption of the F1 endocrine system by tralopyril persisted into adulthood, indicating a transgenerational effect. Molecular docking analysis suggested that tralopyril's RA receptor activity might be one of the key factors contributing to the developmental toxicity observed in offspring. Overall, our study highlights the potential threat posed by tralopyril to the sustainability of fish populations, as it can disrupt the endocrine system and negatively impact aquatic organisms for multiple generations.

Molecular underpinnings underlying behaviors changes in the brain of juvenile common carp (Cyrinus carpio) in response to warming

IntroductionGlobal warming is increasing interest in how aquatic animals can adjust their physiological performance and cope with temperature changes. Therefore, understanding the behavioral changes and molecular underpinnings in fish under warming is crucial for both the individual and groups survival. This could provide experimental evidence and resource for evaluating the impact of global warming. ObjectiveThree genetic families of common carp (Cyprinus carpio) were generated. These juveniles were constructed short-term (4 days) and long-term (30 days) warming groups to investigate the effects of warming on behavioral responses and to elucidate the potential underlying mechanisms of warming-driven behavior. MethodsBehavioral tests were used to explore the effects of short- and long-term exposure to warming on the swimming behavior of C. carpio. Brain transcriptome combined with measurement of nervous system activity was used to further investigated the comprehensive neuromolecular mechanisms under warming. ResultsLong-term warming groups had a more significant impact on the decline of swimming behavior in juvenile C. carpio. Furthermore, brain comparative transcriptomic analysis combined with measurement of nervous system activity revealed that genes involved in cytoskeletal organization, mitochondrial regulation, and energy metabolism are major regulators of behavior in the juvenile under warming. Importantly, especially in the long-term warming groups, enrichment analysis of associated gene expression suggested functional alterations of synaptic transmission and signal transduction leading to swimming function impairment in the central nervous system, as revealed by behavioral tests. ConclusionsOur study provides evidence of the neurogenomic mechanism underlying the decreased swimming activity in juvenile C. carpio under warming. These findings have important implications for understanding the impacts of climate change on aquatic ecosystems and the organisms that inhabit them.

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.

Life history traits of low-toxicity alternative bisphenol S on Daphnia magna with short breeding cycles: A multigenerational study

Due to relatively lower toxicity, bisphenol S (BPS) has become an alternative to previously used bisphenol A. Nevertheless, the occurrence of BPS and its ecological impact have recently attracted increasing attentions because the toxicology effect of BPS with life cycle or multigenerational exposure on aquatic organisms remains questionable. Herein, Daphnia magna (D. magna) multigenerational bioassays spanning four generations (F0–F3) and single-generation recovery (F1 and F3) in clean water were used to investigate the ecotoxicology of variable chronic BPS exposure. For both assays, four kinds of life-history traits (i.e., survival, reproduction, growth and ecological behavior) were examined for each generation. After an 18-day exposure under concentration of 200 μg/L, the survival rate of D. magna was less than 15 % for the F2 generation, whereas all died for the F3 generation. With continuous exposure of four generations of D. magna at environmentally relevant concentrations of BPS (2 μg/L), inhibition of growth and development, prolonged sexual maturity, decreased offspring production and decreased swimming activity were observed for the F3 generation. In particular, it is difficult for D. magna to return to its normal level through a single-generation recovery in clean water in terms of reproductive function, ecological behavior and population health. Hence, multi-generational exposure to low concentrations of BPS can have adverse effects on population health of aquatic organisms with short breeding cycles, highlighting the necessity to assess the ecotoxicology of chronic BPS exposure for public health.

N-acetylcysteine and cysteamine bitartrate prevent azide-induced neuromuscular decompensation by restoring glutathione balance in two novel surf1-/- zebrafish deletion models of Leigh syndrome.

SURF1 deficiency (OMIM # 220110) causes Leigh syndrome (LS, OMIM # 256000), a mitochondrial disorder typified by stress-induced metabolic strokes, neurodevelopmental regression and progressive multisystem dysfunction. Here, we describe two novel surf1-/- zebrafish knockout models generated by CRISPR/Cas9 technology. While gross larval morphology, fertility, and survival into adulthood appeared unaffected, surf1-/- mutants manifested adult-onset ocular anomalies and decreased swimming activity, as well as classical biochemical hallmarks of human SURF1 disease, including reduced complex IV expression and enzymatic activity and increased tissue lactate. surf1-/- larvae also demonstrated oxidative stress and stressor hypersensitivity to the complex IV inhibitor, azide, which exacerbated their complex IV deficiency, reduced supercomplex formation, and induced acute neurodegeneration typical of LS including brain death, impaired neuromuscular responses, reduced swimming activity, and absent heartrate. Remarkably, prophylactic treatment of surf1-/- larvae with either cysteamine bitartrate or N-acetylcysteine, but not other antioxidants, significantly improved animal resiliency to stressor-induced brain death, swimming and neuromuscular dysfunction, and loss of heartbeat. Mechanistic analyses demonstrated cysteamine bitartrate pretreatment did not improve complex IV deficiency, ATP deficiency, or increased tissue lactate but did reduce oxidative stress and restore glutathione balance in surf1-/- animals. Overall, two novel surf1-/- zebrafish models recapitulate the gross neurodegenerative and biochemical hallmarks of LS, including azide stressor hypersensitivity that was associated with glutathione deficiency and ameliorated by cysteamine bitartrate or N-acetylcysteine therapy.

A Comparison of Different Tournament Weigh‐In Formats on the Short‐Term Postrelease Behavior of Black Bass Assessed with Biologgers

AbstractBlack bass Micropterus spp. live‐release tournaments are a popular activity in North America. Efforts continue to further increase survival and enhance welfare of fish released from competitive angling events. Recently, some tournaments have adopted a new weigh‐in format in which black bass are weighed immediately (hanging from a scale in air) and released at the capture location. More conventional tournaments involve retaining black bass in a live well and delivering them to a central location to be weighed (wet or dry weigh‐in). We used biologgers that measured swimming activity, depth selection, and water temperature selection to examine how different weigh‐in formats alter postrelease behavior of Smallmouth Bass M. dolomieu and Largemouth Bass M. salmoides. All fish showed a significant decrease in swimming activity as time progressed during the 10‐min monitoring period, regardless of the weigh‐in format. Swimming activity remained elevated (i.e., hyperactivity) for a longer period of time for black bass that were retained in live wells compared to those that were subjected to the catch, weigh, and release weigh‐in format and the control (fish that were caught and immediately released without air exposure). Swimming activity of black bass tended to decrease as they achieved greater depths with cooler water temperatures. For both species, the water temperature selected postrelease was influenced by the weigh‐in format. Black bass that were dry weighed and wet weighed spent more time in warmer water temperatures than fish in the control group or fish that were caught, weighed, and released. This study suggests that to reduce behavioral alterations associated with wet or dry weigh‐ins, tournament organizations need to carefully select the weigh‐in location, allowing easy access to refuge (i.e., habitat complexity similar to that of the capture location) having the cooler water temperatures commonly associated with deeper water. These results also suggest that catch, weigh, and release formats could be beneficial for black bass during periods of the year with elevated water temperature.

Individual and combined multigenerational effects induced by polystyrene nanoplastic and glyphosate in Daphnia magna (Strauss, 1820)

In this study, the acute and multigenerational effects of the individual and combined toxicity of polystyrene nanoplastic (PSNP - 15.6, 31.2 62.5, 125, 250 and 500 mg/L) and glyphosate (Gly - 6.2, 12.5, 25, 50, 100 and 200 mg/L) on the freshwater crustacean Daphnia magna were investigated. The acute toxicity interactions were predicted mathematically using Abbott's model and multiple toxicological endpoints. In the multigenerational tests, we evaluated the effects in filial (F1 and F2) generations of daphnids after parental (F0) exposure to Gly and PSNP, as individual compounds and as a mixture, during their life history. Based on Abbott's model, the combined individual toxicities of Gly and PSNP are increased when they are present as a mixture. This indicates synergy between the components of the mixture, especially in the case of co-exposure to Gly and PSNP in higher equitoxic proportions. The mixture of PSNP and Gly caused an increase in immobility and ROS production and decrease in swimming activity. Multigenerational responses indicated that the exposure of F0 daphnids to Gly and PSNP as a mixture induced effects in the F1 and F2 reproduction parameters in the recovery tests. Thus, the results reported herein provide important information on the interaction of hydrophilic organic and nanoplastic pollutants in aqueous ecosystems. This will be useful in future studies on the toxicity of mixtures and multigenerational effects and provide a basis for management decisions aimed at the protection of environmental health.

Microplastics alone or co-exposed with copper induce neurotoxicity and behavioral alterations on zebrafish larvae after a subchronic exposure.

Microplastics (MPs, <5mm) have been frequently detected in aquatic ecosystems, representing both health and ecological concerns. However data about the combined effects of MPs and other contaminants is still limited. This study aimed to evaluate the impact of MPs and the heavy metal copper (Cu) on zebrafish (Danio rerio) larvae development and behavior. Zebrafish embryos were subchronically exposed to MPs (2mg/L), two sub-lethal concentrations of Cu (60 and 125µg/L) and binary mixtures of MPs and Cu using the same concentrations, from 2-h post fertilization until 14 days post fertilization. Lethal and sub-lethal responses (mortality, hatching, body length) were evaluated during the embryogenesis period, and locomotor, avoidance, anxiety and shoaling behaviors, and acetylcholinesterase (AChE) activity were measured at 14 dpf. The results showed that survival of larvae was reduced in groups exposed to MPs, Cu and Cu+MPs. Regarding the behavioral patterns, the higher Cu concentration and mixtures decreased significantly the mean speed, the total distance traveled and the absolute turn angle, demonstrating an adverse effect on swimming competence of zebrafish larvae. Exposure to MPs and Cu, alone or combined, also affected avoidance behavior of zebrafish, with larvae not reacting to the aversive stimulus. There was a significant inhibition of AChE activity in larvae exposed to all experimental groups, compared to the control group. Moreover, a higher inhibition of AChE was noticed in larvae exposed to MPs and both Cu+MPs groups, comparatively to the Cu alone groups. Our findings demonstrate the adverse effects of MPs, alone or co-exposed with Cu, on fish early life stages behavior. This study highlights that MPs and heavy metals may have significant impacts on fish population fitness by disrupting locomotor and avoidance behaviors.

The Effects of Live Feeding on Swimming Activity and Exhibit Use in Zoo Humboldt Penguins (Spheniscus humboldti)

Penguins are considered among the most popular animals for zoo and aquarium visitors to observe. Swimming is considered a desirable activity, both for the visitor experience and the welfare of the penguins. However, little is known about the amount of time exhibited penguins spend swimming, or how such swimming is related to regular feeding events. We examined the effects of introducing live prey in the form of trout on 22 Humboldt penguins living at the Woodland Park Zoo. Of primary interest was how the live feeds changed (1) daily and hourly swimming activity, and (2) variability in enclosure use. We hypothesized that the live feedings would increase swimming activity prior to and during the delivery of the live trout, as well as create an overall increase in total swimming activity for live feed days compared to non-live feed days. We also predicted that the penguins would be more likely to use the entire exhibit around these live feeds, since they are likely to chase fish throughout the exhibit. Penguins did show an increase in swimming activity in the hour prior to and during the live feed, with a small decrease in swimming activity following the live feed when compared to non-live feed days. There was also a more than 30% increase in the total swimming activity for live feed days when compared to all other non-live feed days. In addition, a single measure of variability in enclosure use (entropy) showed greater overall enclosure use for the live feed days compared to the non-live feed days. These results demonstrate that live fish can be a useful way of enriching the behavioural welfare of Humboldt penguins.

Artificial Light at Night Alters the Physiology and Behavior of Western Mosquitofish (Gambusia affinis)

Human population growth and its associated effects on the environment contribute to the rapid decrease of biodiversity worldwide. Artificial light at night (ALAN) is an anthropogenic pollutant that is increasing with the spread of urbanization and may contribute to biodiversity declines. ALAN alters the migration patterns of birds, communication in frogs, and impacts reproduction, behavior, and physiology of multiple other taxa. However, most of the studies on ALAN are based on terrestrial systems, and overall, the effects of ALAN on freshwater organisms are poorly understood. We investigated how ALAN affects the physiology, behavior, and reproduction of a widespread, tolerant species of freshwater fish.Gambusia affinisare small livebearing fish often found in urban streams. We exposed groups of femaleG. affinisto either a natural light cycle or a constant 24-h light cycle (ALAN) in the laboratory for 60 days. In another experiment, we exposed femaleG. affinisto the same treatments in outdoor mesocosms for 32 days. We found that exposure to ALAN lowered glucose levels in the brain and decreased swimming activity, but had no effect on cortisol release rates, reproduction, survival, or growth. This research is strengthened by measuring multiple metrics in response to ALAN and by incorporating both a field and laboratory component which confirm similar results. These results suggest that this tolerant species of fish may behaviorally adjust to ALAN rather than modulate their endocrine stress response.

The neurophysiological effects of iron in early life stages of zebrafish

Trace metal/ion homeostasis, neurophysiological performance, and molecular responses to iron (Fe) exposure were investigated in the model organism zebrafish (Danio rerio). The findings demonstrated that exposure to a sublethal concentration of ferric iron (Fe3+) increased Fe contents in both the whole body and head region of developing zebrafish. Among the various trace metals and major ion examined, a dysregulation in manganese, zinc, nickel, and calcium balance was also observed in Fe-exposed larvae. Further biochemical assay and in-vivo imaging revealed that Fe exposure resulted in possible oxidative stress-induced damage, and an increased generation of reactive oxygen species in specific regions of the larvae. Using a droplet digital PCR (ddPCR) technology, it was found that the expression levels of various oxidative stress-responsive genes were temporally modulated by Fe exposure. Additionally, Fe-exposed larvae exhibited an impairment in escape response and a decrease in swimming activity. These larvae also appeared to exhibit a reduced anxiety-like behaviour. Together, our research suggested that larvae experiencing an increased Fe loading exhibited a dysregulation in metal homeostasis and a decrease in neurophysiological performance. These results suggested that neurophysiological assessments are sensitive methods to evaluate Fe toxicity in developing fish.

Polystyrene microplastics impaired the feeding and swimming behavior of mysid shrimp Neomysis japonica.

Growing evidences revealed the deleterious impacts of microplastics (MPs) on marine organisms. However, the effects of MPs on the movement behavior of marine crustacean is poorly understood. Therefore, this study aims to evaluate the physiological and behavioral responses of mysid shrimp (Neomysis japonica) larvae to polystyrene (PS) and carboxylated polystyrene (PS-COOH). PS-COOH presented a greater physiological toxicity to shrimp larvae compared to PS, causing significant lethal and growth inhibition effect, owing to bioaccumulation of MPs inside stomach. Both two MPs decreased the feeding efficiency of larvae, showing weakened predation competence. Moreover, reduced hunting and/or explorative ability of shrimps caused by MPs was also identified, which was evidenced by an overall decrease in swimming activity, range and frequency after exposure. Our study firstly highlighted that micron-sized polystyrene particles had the negative effects on the movement behavior of mysid shrimp larvae, thus posing potential hazard to population dynamics and ecological function of marine crustacean.

Increased Mortality, Delayed Hatching, Development Aberrations and Reduced Activity in Brown Trout (Salmo trutta) Exposed to Phenethyl Isothiocyanate

Plants of the order Brassicaceae have evolved a chemical defence against herbivory: the glucosinolate-myrosinase system. Mechanical damage to plant tissues, such as grazing, initiates the production of phenethyl isothiocyanate (PEITC), a compound toxic to invertebrates. Mechanical damage caused during biofumigation and the harvesting and washing of watercress presents routes for PEITC release into waterbodies, such as the chalk stream spawning sites of brown trout (Salmo trutta). This laboratory study exposed developing S. trutta embryos to PEITC at concentrations of 0.01, 0.1 and 1 μg/L. S. trutta exposed to 1 μg/L PEITC during embryonic development resulted in 100% mortality after four dose days. Exposure to 0.1 μg/L PEITC resulted in an approximate fourfold increase in mortality relative to the controls, while exposure to 0.01 μg/L PEITC had a negligible effect on embryo mortality. Embryos exposed to 0.1 μg/L PEITC showed a significant delay in hatching and produced alevins with significantly shorter total lengths, lighter body weights and an approximate threefold increase in spinal deformities relative to those exposed to the controls and 0.01 μg/L PEITC. The results of a motor activity assay demonstrate that alevins exposed to PEITC showed a significant decrease in swimming activity compared with control animals during periods of illumination. The increased mortality, teratogenic effects and impaired behaviour in S. trutta following embryonic exposure to relatively low concentrations of PEITC highlight a need to accurately quantify and monitor environmental levels of PEITC.

Changes in thyroid hormone activity disrupt photomotor behavior of larval zebrafish

High throughput in vitro, in silico, and computational approaches have identified numerous environmental chemicals that interfere with thyroid hormone (TH) activity, and it is posited that human exposures to such chemicals are a contributing factor to neurodevelopmental disorders. However, whether hits in screens of TH activity are predictive of developmental neurotoxicity (DNT) has yet to be systematically addressed. The zebrafish has been proposed as a second tier model for assessing the in vivo DNT potential of TH active chemicals. As an initial evaluation of the feasibility of this proposal, we determined whether an endpoint often used to assess DNT in larval zebrafish, specifically photomotor behavior, is altered by experimentally induced hyper- and hypothyroidism. Developmental hyperthyroidism was simulated by static waterborne exposure of zebrafish to varying concentrations (3–300 nM) of thyroxine (T4) or triiodothyronine (T3) beginning at 6 h post-fertilization (hpf) and continuing through 5 days post-fertilization (dpf). Teratogenic effects and lethality were observed at 4 and 5 dpf in fish exposed to T4 or T3 at concentrations >30 nM. However, as early as 3 dpf, T4 (> 3 nM) and T3 (> 10 nM) significantly increased swimming activity triggered by sudden changes from light to dark, particularly during the second dark period (Dark 2). Conversely, developmental hypothyroidism, which was induced by treatment with 6-propyl-2-thiouracil (PTU), morpholino knockdown of the TH transporter mct8, or ablation of thyroid follicles in adult females prior to spawning, generally decreased swimming activity during dark periods, although effects did vary across test days. All effects of developmental hypothyroidism on photomotor behavior occurred independent of teratogenic effects and were most robust during Dark 2. Treatment with the T4 analog, Tetrac, restored photomotor response in mct8 morphants to control levels. Collectively, these findings suggest that while the sensitivity of photomotor behavior in larval zebrafish to detect TH disruption is influenced by test parameters, this test can distinguish between TH promoting and TH blocking activity and may be useful for assessing the DNT potential of TH-active chemicals.

Varying the exposure period and duration of neuroactive pharmaceuticals and their metabolites modulates effects on the visual motor response in zebrafish (Danio rerio) larvae

Pharmaceuticals and personal care products are emerging contaminants that are increasingly detected in surface waters around the world. Despite the rise in environmental detections, measured concentrations are still typically low, raising the importance of environmental risk assessments that focus on ecologically relevant sublethal endpoints, such as altered behavior. Neuroactive pharmaceuticals, like mental health medications, pain killers, etc., may be particularly potent in this regard as they are specifically designed to cause behavioral changes without causing physiologic impairment in mammalian systems. We screened 15 different popular neuroactive pharmaceuticals, ranging from antidepressants (including 3 major antidepressant metabolites), anxiety medications, and pain killers, under three different exposure scenarios (repeated, late acute and early transient exposure) to look for behavioral effects in larval zebrafish using the visual motor response (VMR). Drugs were screened at 0, 1, 10, and 100 μg/L in the repeated exposure scenario, and at 0 and 100 μg/L in the late acute and early transient exposure scenarios. Eight of the 15 compounds tested, specifically the antidepressants amitriptyline, fluoxetine, nor-fluoxetine, paroxetine, sertraline, nor-sertraline, venlafaxine, and the antipsychotic drug haloperidol decreased swimming activity by 25% to 40% under repeated exposure conditions. Five of the compounds (amitriptyline, fluoxetine, nor-fluoxetine, paroxetine, and sertraline) also significantly decreased activity by 17% to 31% in the late acute exposure paradigm. Three compounds (fluoxetine, paroxetine and venlafaxine) significantly altered swimming activity with early transient exposure, however creating a hyperactive response and increasing activity from 24% to 28%, while haloperidol significantly decreased activity by 31%. This paper is, to our knowledge, the first to screen so many neuroactive pharmaceuticals, including major metabolites, in parallel under multiple exposure conditions. We show that antidepressants most consistently alter VMR swimming activity. Additionally, we show that major antidepressant metabolites can potentially alter behavior as much as their parent compounds. Furthermore, we show that the magnitude and direction of behavioral effect is dependent on the exposure duration and period, indicating that a more diverse experimental approach might be needed to more accurately assess the risk these compounds pose to the environment.

Behavioral effects of copper on larval white sturgeon.

Early-life stage white sturgeon are sensitive to copper (Cu), with adverse behavioral responses observed during previous studies. The objectives of the present study were to quantify the effects of Cu exposure on white sturgeon swimming and feeding behaviors and determine their time to response. Larval sturgeon (1-2, 28, or 35 d posthatch [dph]) were exposed to Cu (0.5-8 μg/L) for 4 to 14 d. Abnormal behavioral changes were observed within the first few days of exposure including loss of equilibrium and immobilization. Digital video tracking software revealed decreased swimming activity with increasing Cu concentration. Significant changes in behavior and mortality occurred at concentrations of Cu between 1 and 8 μg/L. Juvenile white sturgeon, 58 dph, exposed to 12 μg/L Cu consumed 37 to 60% less food than controls after 3 d of exposure. The present results indicate that behavioral endpoints were more sensitive than some standard toxicity test endpoints and can effectively expand the sensitivity of standard toxicity tests for white sturgeon. Swimming behavior was impaired to the extent that survival in the field would likely be jeopardized. Such data would provide managers a useful metric for characterizing the risks of Cu contamination to white sturgeon. Environ Toxicol Chem 2019;38:132-144. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.