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1.
Environ Sci Pollut Res Int ; 27(23): 29341-29351, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32440876

RESUMO

The synthetic estrogen, 17-α-ethinylestradiol (EE2), present in contraceptive pills, is an endocrine-disrupting chemical (EDC) that can be found in the aquatic environment. We examined the impacts of EE2 on zebrafish behavioral and physiological responses through the novel tank test (NTT), which measures anxiety-like behavior; the mirror-induced aggression (MIA) test, which measures aggressiveness; and the social preference test (SPT), which measures social cohesion. The steroid hormone levels were also measured. Here, we show that exposure to EE2 impairs stress responses by regulating the levels of specific hormones and eliciting an anxiolytic response, increasing aggression, and reducing social preference in zebrafish. In nature, these changes in behavior compromise reproduction and anti-predator behaviors, which, in turn, affects species survival. The maintenance of an intact behavioral repertoire in zebrafish is essential for their survival. Thus, our results point to the danger of environmental contamination with EE2 as it may alter the dynamics of the prey-predator relationship.


Assuntos
Poluentes Químicos da Água , Peixe-Zebra , Animais , Etinilestradiol , Reprodução
2.
Arch Environ Contam Toxicol ; 77(3): 443-451, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31190101

RESUMO

Environmental contamination caused by the human occupancy and economic activities that generate a wide range of contaminated effluents that reach natural water resources, is a current reality. Residues of agrichemicals used in plant production were detected in different environments and in different countries. Among these agrochemicals, we studied a glyphosate-based herbicide (GBH), a fipronil-based insecticide (FBI), and their mixtures (GBH + FBI). Zebrafish exposed to 3 and 5 mg/L of GBH spend more time in the top zone and less time in the bottom zone. Fish exposed to 0.009 and 0.018 mg/L of FBI spent less time in the bottom zone, whereas zebrafish exposed to the three GBH + FBI mixtures spend more time in the top zone compared with unexposed control fish. This clear anxiolytic pattern, in an environmental context, can directly impair the ability of fish to avoid or evade predators. We concluded that both glyphosate-based herbicide and fipronil-based insecticide and their mixtures alter zebrafish behavior, which may result in significant repercussions on the maintenance of the species as well as on the food chain and the ecosystem.


Assuntos
Glicina/análogos & derivados , Praguicidas/toxicidade , Pirazóis/toxicidade , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/fisiologia , Animais , Comportamento Animal/efeitos dos fármacos , Ecossistema , Feminino , Glicina/toxicidade , Humanos , Masculino , Comportamento Predatório
3.
Sci Rep ; 8(1): 13908, 2018 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-30224742

RESUMO

Here we show that the novel object recognition test can discriminate between high (HRN, neophobic) and low (LRN, neophilic) novelty responders in zebrafish populations. Especially when we observe the latency to the first entry in the novel object zone, zebrafish did not maintain these behavioral phenotypes in sequential tests and only the HRN group returned to their initial responsive behavior when exposed to fluoxetine. Our results have important implications for behavioral data analysis since such behavioral differences can potentially increase individual response variability and interfere with the outcomes obtained from various behavioral tasks. Our data reinforce the validity of personality determination in zebrafish since we show clear differences in behavior in response to fluoxetine.


Assuntos
Comportamento Animal/efeitos dos fármacos , Fluoxetina/farmacologia , Peixe-Zebra/fisiologia , Animais , Masculino
4.
Behav Brain Res ; 336: 85-92, 2018 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-28822694

RESUMO

Studies with zebrafish use acclimatizing periods of at least one week immediately before the experiments. During this time, animals can be housed in sexually segregated conditions (only females or males in the tank) or in mixed-sex conditions (both sexes in the tank). The influence of sex and housing conditions regarding the presence of one or two sexes is largely unknown in zebrafish. Our aim was to evaluate the influence that sex and housing regarding the sex of animals had in the open tank task, in the inhibitory avoidance memory test, in cortisol levels and weight in zebrafish. Four groups of animals were used: 1) segregated housed females (only females were kept in the tank); 2) segregated housed males (only males were kept in the tank); 3) mixed-sex housed females (only females were analyzed from a tank containing 50% ratio of each sex); 4) mixed-sex housed males (only males were analyzed from a tank containing 50% ratio of each sex). Males showed higher total distance travelled and mean speed when compared to females. In the inhibitory avoidance memory, sexually segregated animals had higher latencies than their mixed-sex counterparts in the 1day test and sexually segregated females presented a memory that persisted longer and was able to be reinstated. Whole-body cortisol levels were higher in mixed-sex animals while weight was lower in these fish. To the best of our knowledge, this is the first time that effects of sex and housing regarding sex were investigated in behavior and physiology of zebrafish.


Assuntos
Peixe-Zebra/fisiologia , Animais , Comportamento Animal/fisiologia , Peso Corporal/fisiologia , Feminino , Abrigo para Animais , Hidrocortisona/análise , Masculino , Fatores Sexuais , Comportamento Sexual
5.
Sci Rep ; 7(1): 14121, 2017 10 26.
Artigo em Inglês | MEDLINE | ID: mdl-29074994

RESUMO

The ability to avoid and escape from predators are clearly relevant behaviors from the ecological perspective and directly interfere with the survival of organisms. Detected in the aquatic environment, risperidone can alter the behavior of exposed species. Considering the risk of exposure in the early stages of life, we exposed zebrafish embryos to risperidone during the first 5 days of life. Risperidone caused hyperactivity in exposed larvae, which in an environmental context, the animals may be more vulnerable to predation due to greater visibility or less perception of risk areas.


Assuntos
Comportamento Animal/efeitos dos fármacos , Resíduos de Drogas/farmacologia , Larva/efeitos dos fármacos , Psicotrópicos/farmacologia , Risperidona/farmacologia , Poluentes Químicos da Água/farmacologia , Peixe-Zebra , Animais , Relação Dose-Resposta a Droga
6.
Gen Comp Endocrinol ; 252: 236-238, 2017 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-28716505

RESUMO

In this article, we show that the tyrosine hydroxylase inhibitor α-Methyl-l-tyrosine (AMPT) decreased the responsiveness of the zebrafish stress axis to an acute stressful challenge. These effects were specific for responses to stimulation, since unstimulated (basal) cortisol levels were not altered by AMPT. Moreover, AMPT decreased the stress response 15min after stimulation, but not after that time period. To our knowledge, this is the first report about the effects of AMPT on the neuroendocrine axis of adult zebrafish in acute stress responses. Overall, these results suggest a mechanism of catecholamine-glucocorticoid interplay in neuroendocrine responses of fish, pointing an interesting avenue for physiological research, as well as an important endpoint that can be disrupted by environmental contamination. Further experiments will unravel the mechanisms by which AMPT blocked the cortisol response.


Assuntos
Inibidores Enzimáticos/farmacologia , Estresse Fisiológico/efeitos dos fármacos , Tirosina 3-Mono-Oxigenase/antagonistas & inibidores , Peixe-Zebra/fisiologia , alfa-Metiltirosina/farmacologia , Animais , Feminino , Hidrocortisona/sangue , Masculino , Tirosina 3-Mono-Oxigenase/metabolismo , Peixe-Zebra/sangue
7.
Environ Toxicol ; 32(7): 1964-1972, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28371364

RESUMO

The glucocorticoid cortisol, the end product of hypothalamus-pituitary-interrenal axis in zebrafish (Danio rerio), is synthesized via steroidogenesis and promotes important physiological regulations in response to a stressor. The failure of this axis leads to inability to cope with environmental challenges preventing adaptive processes in order to restore homeostasis. Pesticides and agrichemicals are widely used, and may constitute an important class of environmental pollutants when reach aquatic ecosystems and nontarget species. These chemical compounds may disrupt hypothalamus-pituitary-interrenal axis by altering synthesis, structure or function of its constituents. We present evidence that organophosphorus exposure disrupts stress response by altering the expression of key genes of the neural steroidogenesis, causing downregulation of star, hsp70, and pomc genes. This appears to be mediated via muscarinic receptors, since the muscarinic antagonist scopolamine blocked these effects.


Assuntos
Disruptores Endócrinos/toxicidade , Inseticidas/toxicidade , Metil Paration/toxicidade , Receptores Muscarínicos/metabolismo , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/metabolismo , Animais , Proteínas de Choque Térmico HSP72/genética , Proteínas de Choque Térmico HSP72/metabolismo , Hidrocortisona/metabolismo , Locomoção/efeitos dos fármacos , Antagonistas Muscarínicos/farmacologia , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Pró-Opiomelanocortina/genética , Pró-Opiomelanocortina/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , RNA Mensageiro/metabolismo , Escopolamina/farmacologia , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismo
8.
Neurosci Lett ; 650: 114-117, 2017 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-28445770

RESUMO

Several studies have reported the presence of methylphenidate (MPH) in effluents; however, its impacts on aquatic life are not yet well understood. Here, we investigated the effects of acute exposure on endocrine and behavioral stress responses to environmentally relevant concentrations of MPH in zebrafish. We show that MPH blunts the response of cortisol to stress in zebrafish. On the other hand, MPH stresses fish per se. Additionally, MPH seems to modulate anxiety-like behaviors. We conclude that the presence of MPH in aquatic environments can alter neuroendocrine and behavior responses, which might considerably impact fish survival and welfare.


Assuntos
Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Hidrocortisona/metabolismo , Metilfenidato/administração & dosagem , Estresse Fisiológico/efeitos dos fármacos , Poluentes Químicos da Água/administração & dosagem , Peixe-Zebra/fisiologia , Animais , Estimulantes do Sistema Nervoso Central/administração & dosagem , Relação Dose-Resposta a Droga , Sistema Endócrino/efeitos dos fármacos , Sistema Endócrino/fisiologia , Feminino , Humanos , Estresse Fisiológico/fisiologia
9.
Zebrafish ; 14(1): 51-59, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27672711

RESUMO

In this study, we show that an adaptation of the spinning test can be used as a model to study the exercise-exhaustion-recovery paradigm in fish. This forced swimming test promotes a wide range of changes in the hypothalamus-pituitary-interrenal axis functioning, intermediary metabolism, as well in fish behavior at both exercise and recovery periods. Our results pointed that this adapted spinning test can be considered a valuable tool for evaluating drugs and contaminant effects on exercised fish. This can be a suitable protocol both to environmental-to evaluate contaminants that act in fish energy mobilization and recovery after stressors-and translational perspectives-effects of drugs on exercised or stressed humans.


Assuntos
Glucose/análise , Hidrocortisona/análise , Condicionamento Físico Animal/métodos , Natação , Peixe-Zebra/fisiologia , Animais , Comportamento Animal , Creatina Quinase/análise , Metabolismo Energético , Modelos Animais , Estresse Fisiológico , Peixe-Zebra/sangue
10.
Sci Rep ; 6: 37612, 2016 11 22.
Artigo em Inglês | MEDLINE | ID: mdl-27874070

RESUMO

Here we provide, at least to our knowledge, the first evidence that aripiprazole (APPZ) in the water blunts the stress response of exposed fish in a concentration ten times lower than the concentration detected in the environment. Although the mechanism of APPZ in the neuroendocrine axis is not yet determined, our results highlight that the presence of APPZ residues in the environment may interfere with the stress responses in fish. Since an adequate stress response is crucial to restore fish homeostasis after stressors, fish with impaired stress response may have trouble to cope with natural and/or imposed stressors with consequences to their welfare and survival.


Assuntos
Aripiprazol/toxicidade , Estresse Fisiológico/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/fisiologia , Animais , Feminino , Hidrocortisona/metabolismo , Masculino
11.
Arch Environ Contam Toxicol ; 71(3): 415-22, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27423874

RESUMO

In agriculture intensive areas, fishponds and natural water bodies located in close proximity to these fields receive water with variable amounts of agrichemicals. Consequently, toxic compounds reach nontarget organisms. For instance, aquatic organisms can be exposed to tebuconazole-based fungicides (TBF), glyphosate-based herbicides (GBH), and atrazine-based herbicides (ABH) that are potentially dangerous, which motivates the following question: Are these agrichemicals attractant or aversive to fish? To answer this question, adult zebrafish were tested in a chamber that allows fish to escape from or seek a lane of contaminated water. This attraction and aversion paradigm was evaluated with zebrafish in the presence of an acute contamination with these compounds. We showed that only GBH was aversive to fish, whereas ABH and TBF caused neither attraction nor aversion for zebrafish. Thus, these chemicals do not impose an extra toxic risk by being an attractant for fish, although TBF and ABH can be more deleterious, because they induce no aversive response. Because the uptake and bioaccumulation of chemicals in fish seems to be time- and dose-dependent, a fish that remains longer in the presence of these substances tends to absorb higher concentrations than one that escapes from contaminated sites.


Assuntos
Agroquímicos/toxicidade , Peixes/fisiologia , Poluentes Químicos da Água/toxicidade , Animais , Aprendizagem da Esquiva , Comportamento Animal , Testes de Toxicidade , Peixe-Zebra
12.
J Toxicol Environ Health A ; 79(1): 1-7, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26699931

RESUMO

Fish production ponds and natural water body areas located in close proximity to agricultural fields receive water with variable amounts of agrochemicals, and consequently, compounds that produce adverse effects may reach nontarget organisms. The aim of this study was to investigate whether waterborne methyl-parathion-based insecticide (MPBI) affected gene expression patterns of brain glucocorticoid receptor (GR), steroidogenic acute regulatory protein (StAR), and heat shock protein 70 (hsp70) in adult zebrafish (Danio rerio) exposed to this chemical for 96 h. Treated fish exposed to MPBI-contaminated water showed an inhibition of brain StAR and hsp70 gene expression. Data demonstrated that MPBI produced a decrease brain StAR and hsp70 gene expression.


Assuntos
Química Encefálica/efeitos dos fármacos , Proteínas de Choque Térmico HSP70/biossíntese , Inseticidas/toxicidade , Metil Paration/toxicidade , Fosfoproteínas/biossíntese , Agroquímicos/toxicidade , Animais , Expressão Gênica/efeitos dos fármacos , Masculino , Receptores de Glucocorticoides/biossíntese , Receptores de Glucocorticoides/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Peixe-Zebra
13.
Physiol Behav ; 139: 182-7, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25449397

RESUMO

Here, we show that individually housed zebrafish presented a reduced cortisol response to an acute stressor (persecution with a pen net for 120 s) compared to zebrafish housed in groups of 10. We hypothesized that the cortisol response to stress was reduced in individually housed zebrafish because they depend solely on their own perceptions of the stressor, whereas among grouped zebrafish, the stress response might be augmented by chemical and/or behavioral cues from the other members of the shoal. This hypothesis was based on previous described chemical communication of stress in fish as well on individual variation in stressor perception and potential individual differences in fish personality.


Assuntos
Hidrocortisona/metabolismo , Comportamento Social , Isolamento Social , Estresse Psicológico/fisiopatologia , Peixe-Zebra/fisiologia , Animais , Feminino , Abrigo para Animais , Masculino , Percepção , Isolamento Social/psicologia
14.
Chemosphere ; 112: 85-91, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25048892

RESUMO

We studied the stress response of Rhamdia quelen fingerlings at 45, 90, 135 and 180 d following acute exposure to agrichemicals. Herein, we report the novel observation that acute exposure of fingerling-aged fish to a methyl parathion-based insecticide (MPBI) and to a tebuconazole-based fungicide (TBF) induced chronic inhibition of the stress response. In contrast, fish exposed to an atrazine-simazine-based herbicide (ASBH) recovered the stress response on day 45, and fish exposed to a glyphosate-based herbicide (GBH) did not present stress response inhibition. Additionally, fish exposed to MPBI, GBH and ASBH showed lower survival rates and attained lower final weights. In the case of TBF, the presence of the stressful stimulus more strongly influenced the changes in the performance parameters than did the agrichemical exposure itself. An impairment of the cortisol response may seriously hamper the adaptive response and the ability to promote the necessary metabolic and ionic adjustments to respond to environmental stress.


Assuntos
Peixes-Gato/fisiologia , Hidrocortisona/antagonistas & inibidores , Praguicidas/toxicidade , Estresse Fisiológico/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Animais , Metil Paration/toxicidade , Taxa de Sobrevida , Fatores de Tempo
15.
Physiol Behav ; 128: 232-6, 2014 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-24548683

RESUMO

We investigated a group of Rhamdia quelen females during their entire first reproductive cycle and beginning of the 2nd cycle by evaluating the stress response at different phases of gonadal maturation. In mammals, including humans, pubertal development modulates stress response reactivity due to the maturation of the neuroendocrine stress axis. These shifts in the stress reactivity were also detected in salmonid fishes. This effect comes from changes in the sensitivity of the stress axis glands or in the capacity of the adrenal tissue to synthesise glucocorticoids. Here, for the first time, we show that similar to mammals and salmonid fishes, pre-pubertal female R. quelen exhibit a protracted stress response compared to adult fish, pointing to puberty as a key event on HPI axis modulation.


Assuntos
Peixes-Gato/fisiologia , Maturidade Sexual/fisiologia , Estresse Fisiológico/fisiologia , Animais , Estradiol/sangue , Feminino , Hidrocortisona/sangue , Reprodução/fisiologia , Testosterona/sangue
16.
PLoS One ; 8(10): e75780, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24116073

RESUMO

The effects of ethanol exposure on Danio rerio have been studied from the perspectives of developmental biology and behavior. However, little is known about the effects of ethanol on the prey-predator relationship and chemical communication of predation risk. Here, we showed that visual contact with a predator triggers stress axis activation in zebrafish. We also observed a typical stress response in zebrafish receiving water from these conspecifics, indicating that these fish chemically communicate predation risk. Our work is the first to demonstrate how alcohol effects this prey-predator interaction. We showed for the first time that alcohol exposure completely blocks stress axis activation in both fish seeing the predator and in fish that come in indirect contact with a predator by receiving water from these conspecifics. Together with other research results and with the translational relevance of this fish species, our data points to zebrafish as a promising animal model to study human alcoholism.


Assuntos
Comunicação Animal , Comportamento Animal/efeitos dos fármacos , Etanol/farmacologia , Comportamento Predatório/efeitos dos fármacos , Animais , Comportamento Animal/fisiologia , Hidrocortisona/metabolismo , Comportamento Predatório/fisiologia , Estresse Fisiológico/fisiologia , Peixe-Zebra/metabolismo
17.
PLoS One ; 8(10): e74499, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24098336

RESUMO

In southern South America and other parts of the world, aquaculture is an activity that complements agriculture. Small amounts of agrichemicals can reach aquaculture ponds, which results in numerous problems caused by oxidative stress in non-target organisms. Substances that can prevent or reverse agrichemical-induced oxidative damage may be used to combat these effects. This study includes four experiments. In each experiment, 96 mixed-sex, 6-month-old Rhamdia quelen (118±15 g) were distributed into eight experimental groups: a control group that was not exposed to contaminated water, three groups that were exposed to various concentrations of bee products, three groups that were exposed to various concentrations of bee products plus tebuconazole (TEB; Folicur 200 CE™) and a group that was exposed to 0.88 mg L(-1) of TEB alone (corresponding to 16.6% of the 96-h LC50). We show that waterborne bee products, including royal jelly (RJ), honey (H), bee pollen (BP) and propolis (P), reversed the oxidative damage caused by exposure to TEB. These effects were likely caused by the high polyphenol contents of these bee-derived compounds. The most likely mechanism of action for the protective effects of bee products against tissue oxidation and the resultant damage is that the enzymatic activities of superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) are increased.


Assuntos
Antioxidantes/farmacologia , Abelhas/metabolismo , Peixes-Gato/metabolismo , Fungicidas Industriais/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Triazóis/toxicidade , Animais , Mel/análise , Pólen/metabolismo
18.
Physiol Behav ; 107(3): 397-400, 2012 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-23017664

RESUMO

In many vertebrate species, including humans, the developmental stage directly influences an organism's reactivity to stress. For instance, fishes appear to exhibit "stress insensitive" periods early in development, which contributes to important alterations in stress responses. This phenomenon raises the important question of whether size or age influences fish stress responses, as there may be large discrepancies in size at any stage of ontogeny. We therefore posed the following question: what key role does the age and/or weight/length of fish play in contributing to different stress levels? To address this question, we conducted 2 simple experiments to compare the cortisol response to stress in the fish Rhamdia quelen. In the first experiment, we compared the cortisol response of fish of 2 different age groups (3 vs. 12 months) with the same body size, whereas in the second experiment we compared 2 groups of the same age (3 months) but with different body sizes. The results showed a similar stress response in fish of the same age but different size, but a large difference in the stress response in fish of the same size but different age. Both tests indicate that age is the determining factor for the functioning of the hypothalamo-pituitary-interrenal (HPI) axis, and is probably related to the stage of maturation. This study makes a significant contribution to our knowledge of the stress, behavior, and welfare of fish of different age classes, primarily with respect to the timing of measurements and the accurate determination of fish age, regardless of size.


Assuntos
Envelhecimento/fisiologia , Tamanho Corporal/fisiologia , Peso Corporal/fisiologia , Hidrocortisona/sangue , Estresse Fisiológico/fisiologia , Envelhecimento/sangue , Animais , Peixes , Fatores de Tempo
19.
Physiol Behav ; 106(2): 129-32, 2012 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-22289300

RESUMO

This study investigated differences in the cortisol response of fish at different developmental stages after exposure to an acute stressor. Three experiments using 126 fish each were performed using 3 different age groups of jundiá (Rhamdia quelen): fingerlings at 60 days of age, juveniles at 180 days, and adults at 360 days. In each experiment, the fish in each group were randomly distributed into either a handled experimental group or a non-handled control group. The handled group was then exposed to an acute stressor for measurement of cortisol concentrations at 5, 15, 30, 60, and 240 min after exposure and subsequent comparison of cortisol concentrations with those of the non-handled groups at the 6 sampling times. Between the experimental and control groups, the results revealed that the handled fish in each of the 3 age groups had higher cortisol concentrations compared to the non-handled fish in the equivalent age group. Among the age groups of the handled fish, the results revealed that the fingerlings and juveniles attained peak cortisol concentrations within 5 to 30 min after stressor exposure whereas the adults attained peak concentrations 60 min after exposure. This finding has important implications for the design of research into stress and welfare among fish at different developmental stages.


Assuntos
Manobra Psicológica , Hidrocortisona/sangue , Fatores Etários , Animais , Peixes-Gato , Estresse Psicológico/sangue , Fatores de Tempo
20.
J Toxicol ; 2011: 280304, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-22253623

RESUMO

Microcystins (MCs) are toxins produced by cyanobacteria (blue-green algae), primarily Microcystis aeruginosa, forming water blooms worldwide. When an organism is exposed to environmental perturbations, alterations in normal behavioral patterns occur. Behavioral repertoire represents the consequence of a diversity of physiological and biochemical alterations. In this study, we assessed behavioral patterns and whole-body cortisol levels of adult zebrafish (Danio rerio) exposed to cell culture of the microcystin-producing cyanobacterium M. aeruginosa (MC-LR, strain RST9501). MC-LR exposure (100 µg/L) decreased by 63% the distance traveled and increased threefold the immobility time when compared to the control group. Interestingly, no significant alterations in the number of line crossings were found at the same MC-LR concentration and time of exposure. When animals were exposed to 50 and 100 µg/L, MC-LR promoted a significant increase (around 93%) in the time spent in the bottom portion of the tank, suggesting an anxiogenic effect. The results also showed that none of the MC-LR concentrations tested promoted significant alterations in absolute turn angle, path efficiency, social behavior, or whole-body cortisol level. These findings indicate that behavior is susceptible to MC-LR exposure and provide evidence for a better understanding of the ecological consequences of toxic algal blooms.

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