Behavioral, biochemical, and endocrine responses of zebrafish to 30-min exposure with environmentally relevant concentrations of imidacloprid-based insecticide.

The imidacloprid-based insecticides (IBIs) are among the most used insecticides worldwide, and chronic and acute toxic effects (days exposure protocols) have been reported in several species in studies of IBIs at lethal concentrations. However, there is little information on shorter time exposures and environmentally relevant concentrations. In this study, we investigated the effect of a 30-min exposure to environmentally relevant concentrations of IBI on the behavior, redox status, and cortisol levels of zebrafish. We showed that the IBI decreased fish locomotion and social and aggressive behaviors and induced an anxiolytic-like behavior. Furthermore, IBI increased cortisol levels and protein carbonylation and decreased nitric oxide levels. These changes were mostly observed at 0.013 and 0.0013 µg·L-1 of IBI. In an environmental context, these behavioral and physiological disbalances, which were immediately triggered by IBI, can impair the ability of fish to evade predators and, consequently, affect their survival.

Exposure to levonorgestrel-based birth control pill in early life and its persistent effects in zebrafish.

The consumption of progestins has increased considerably in recent decades, as has their disposal into the environment. These substances can negatively affect the reproduction, physiology, and behavior of non-target organisms, such as fish. We aimed to evaluate the effects of exposure to environmentally relevant concentrations of levonorgestrel-control birth based (1.3, 13.3, 133, and 1330 ng/L) on the development and behavior of zebrafish (Danio rerio) in terms of mortality, hatching, spontaneous movement, and larval and adult behavioral tests. Exposure caused anxiogenic-like behavior in larvae, which persisted in adults, as demonstrated by the light-dark test. In contrast, it caused anxiolytic-like behavior in the novel tank test. There was a high mortality rate at all tested concentrations and increases in the hormone cortisol at 13.3 ng/L that affected the sex ratio. These changes may lead to an ecological imbalance, emphasizing the risk of early exposure to progestins in the environment.

Dietary transference of 17α-ethinylestradiol changes the biochemical and behavioral biomarkers in adult zebrafish (Danio rerio).

The endocrine disruptors (ED), even in low concentration, can change the homeostasis of an organism through the biochemical and physiological pathways; and are gaining more relevance due to their well-reported presence in the natural environment. EDs mainly affect non-target animals, which can bioaccumulate, leading to changes in metabolism. Another problem is due to several organisms that compose the aquatic biota serving as a basis of the food chain and transferring it to higher trophic levels. Here we evaluated the dietary transference of 17α-ethinylestradiol (EE2), in adult zebrafish chronically fed by EE2-bioaccumulated brine shrimp (BS). For this, we evaluated behavioral biomarkers such as the novel tank test (NTT), social preference test (SPT), mirror-induced aggressivity (MIA), and biochemical biomarkers such as acetylcholinesterase (AChE), superoxide dismutase (SOD), catalase (CTL), and glutathione-S-transferase (GST) activity, cortisol, and lipid peroxidation levels in adult zebrafish. The behavioral effects can be explained by the changed effects on acetylcholinesterase activity as well as in the antioxidant system mainly affected by the high levels of EE2 identified by HPLC shown that had occurred during a dietary transfer for fish. EE2 has a potential pattern for bioaccumulation and dietary transfer in biological tissue and EE2 can affect the behavior of fish. The observed effects could be dangerous to the environment, affecting, other animals and even human health.

Impaired initial development and behavior in zebrafish exposed to environmentally relevant concentrations of widely used pesticides.

Pesticides reach water bodies through different routes, either owing to incorrect packaging disposal, direct application to control macrophytes, leaching from fields, or natural degradation processes. In the aquatic environment, adverse effects in non-target species that come in contact with these substances are poorly understood. Currently, the most used pesticides are glyphosate (GBH) and 2,4-dichlorophenoxyacetic acid-based herbicides (DBH), as its presence in water bodies is already known, we used environmental concentrations and our exposure time comprised the entire period of organogenesis (3-120 h post-fertilization). We evaluated the response of embryos in their early development with the parameters of mortality, hatching, spontaneous movement, and heart rate; and it's through behavior the open field test and aversive stimulus, as well as biochemical analyzes of acetylcholinesterase activity (AChE), catalase (CTL) and superoxide dismutase (SOD) as a possible mechanism of action. Exposure to GBH decreased survival, caused hypermobility and anxiolytic behavior, negatively affected the anti-predatory behavior of the larvae, and increases acetylcholinesterase activity, whereas exposure to DBH caused only slight hypermobility in the larvae and increases acetylcholinesterase activity. These changes may compromise the perpetuation of the species, the search for partners/food, and facilitate the action of predators, which can result in serious ecological consequences.

Embryonic exposure to genistein induces anxiolytic and antisocial behavior in zebrafish: persistent effects until the adult stage.

Genistein is a phytoestrogen, which is structurally similar to 17ß-estradiol. It is present in plants, food, and as a contaminant in effluents. In this article, we demonstrate the effects of embryonic exposure to three different concentrations of genistein (10 µg/L, 40 µg/L, and 80 µg/L) which is similar to those found in effluents. Zebrafish eggs were exposed during the first 72 h post-fertilization (hpf). Heart rate was evaluated at 48 hpf and mortality rate was assessed during the first 72 hpf. The light/dark (LDT) and open field (OFT) behavioral tests were applied to the larvae (6 dpf), and the novel tank (NTT), social preference (SPT), light-dark (LDT), and sexing tests were performed on adult fish (90 dpf). Embryonic exposure to genistein caused anxiolytic-like behavior in both larvae and adult animals. In adult stage, we observed an increase in locomotor activity and antisocial behavior in the concentration of 40 µg/L. There was an increase in the mortality rate in all concentrations when compared to the control and an increase in heart rate at the concentration of 80 µg/L. Exposure to 10 µg/L generated a higher frequency of females when compared to the control group. Our results show that exposure to genistein during the embryonic phase brings damage in the short and long term as it increases the mortality rate and leads to behavioral disorders both in the larval stage, with perpetuation until adult stage. The anxiolytic-like effect and less social interaction are effects that harm fish survival.

Stimulants cocktail: Methylphenidate plus caffeine impairs memory and cognition and alters mitochondrial and oxidative status.

Methylphenidate (MPH) is a psychostimulant widely misused to increase wakefulness by drivers and students. Also, MPH can be found in dietary supplements in a clandestine manner aiming to burst performance of physical exercise practitioners. The abusive use of high doses of caffeine (CAF) in these contexts is equally already known. Here, we demonstrate the behavioral, oxidative and mitochondrial effects after acute exposure to high doses of MPH (80 mg/L) and CAF (150 mg/L), alone or associated (80 mg/L + 150 mg/L, respectively). We used zebrafish as animal model due to its high translational relevance. We evaluated the behavioral effects using the Novel Tank Test (NTT), Social Preference Test (SPT) and Y-maze Task and analyzed biomarkers of oxidative stress and activity of mitochondrial respiratory chain complexes. MPH alone induced antisocial behavior. MPH inhibited lipid peroxidation. The association of MPH + CAF presented memory impairment and anxiogenic behavior. In oxidative status, it inhibited lipid peroxidation, increased protein carbonylation and mitochondrial complex II, III and IV activity. Our results demonstrate that MPH and CAF alone negatively impact the typical behavioral of zebrafish. When associated, changes in cognition, memory, oxidative and mitochondrial status are more relevant.