Assessment of toxicity of pyriproxyfen, Bacillus thuringiensis, and malathion and their mixtures used for mosquito control on embryo-larval development and behavior of zebrafish.

Pyriproxyfen (PPF), Bacillus thuringiensis israelensis (BTI), and malathion (MLT) are widely used worldwide to control the population of mosquitos that transmit arboviruses. The current work aimed to evaluate the toxicity of these single pesticides and their binary mixtures of PPF + BTI, PPF + MLT, and MLT + BTI on the embryo-larval stage of zebrafish (Danio rerio) as an animal model. Epiboly, mortality, apical endpoints, affected animals, heart rate, morphometric, thigmotaxis, touch sensitivity, and optomotor response tests were evaluated. PPF and MLT and all mixtures reduced the epiboly percentage. Mortality increased significantly in all exposed groups, except BTI, with MLT being the most toxic. The observed apical endpoints were pericardial and yolk sac edemas, and tail and spine deformation. Exposure to MLT showed a higher percentage of affected animals. A reduction in heart rate was also observed in MLT- and PPF + MLT-exposed groups. The PPF + MLT mixture decreased head measurements. Behavioral alterations were observed, with a decrease in thigmotaxis and touch sensitivity responses in PPF + MLT and MLT + BTI groups. Finally, optomotor responses were affected in all groups. The above data obtained suggest that the MLT + PFF mixture has the greatest toxicity effects. This mixture affected embryo-larval development and behavior and is close to the reality in several cities that use both pesticides for mosquito control rather than single pesticides, leading to a reevaluation of the strategy for mosquito control.

Single and joint toxic effects of thyroid hormone, levothyroxine, and amiodarone on embryo-larval stages of zebrafish (Danio rerio).

This study evaluates single and joint endocrine disruptor toxicities of thyroid hormone, levothyroxine, and amiodarone in the embryo-larval stages of Danio rerio. Single toxicity experiments were carried out in concentrations based on the environmental concentration and increasing concentrations of 10, 100, and 1000 times the environmental concentration. Joint toxicity experiments evaluated the combined effects of these compounds. Toxic effects were examined during zebrafish embryonic development, and the parameters analyzed were apical sublethal, teratogenicity, mortality endpoints, and morphometry. Thyroid hormone exhibited the highest toxicity. However, the results showed that the environmental concentrations for all 3 compounds had low risk in relation to the parameters studied, such as teratogenic effects and morphometry. The larvae were more affected than embryos, where embryos needed higher concentrations in all experiments, possibly due to the absence of the chorion. The same type of effects were observed in the joint toxicity test, except that a possible antagonistic effect was detected. However, high concentrations showed stronger effects of these toxic compounds on fish development.

Testosterone nanoemulsion produced masculinized Nile tilapia (Oreochromis niloticus).

The objective of this work was to develop a food additive for the sex reversal of Nile tilapia (Oreochromis niloticus) based on a simple oil in water (O/W) nanoemulsion with testosterone propionate for incorporation into commercial feed. Oil screening and evaluation of the organoleptic and physicochemical characteristics were carried out to determine the best formulation. A palatability test was also performed. Sex reversal test was assayed using 5 experimental groups: negative control - macerated feed without hormone; free testosterone - macerated feed with 60 mg/kg of testosterone propionate diluted in ethanol; and macerated feed with testosterone propionate nanoemulsion at a concentration of 30, 60, and 90 mg/kg. Stable nanoemulsions (size 76-210 nm) with testosterone propionate were produced. All nanoemulsion-added feed was palatable to tilapia. We obtained sex reversal values of ≈65, 75, and 72% in the groups of 30, 60, and 90 mg/kg, respectively. We can conclude that the nanoemulsion showed promising results; it is capable of inducing sex reversal in tilapia, is suitable as a commercial product, and has the potential to promote safety for rural staff and reduce the environmental impact of hormones.

Folic acid reduces the ethanol-induced morphological and behavioral defects in embryonic and larval zebrafish (Danio rerio) as a model for fetal alcohol spectrum disorder (FASD).

The objective of this work was to determine whether folic acid (FA) reduces the embryonic ethanol (EtOH) exposure induced behavioral and morphological defects in our zebrafish fetal alcohol spectrum disorder (FASD) model. Teratogenic effects, mortality, the excitatory light-dark locomotion (ELD), sleep (SL), thigmotaxis (TH), touch sensitivity (TS), and optomotor response (OMR) tests were evaluated in larvae (6-7 days post-fertilization) using four treatment conditions: Untreated, FA, EtOH and EtOH + FA. FA reduced morphological defects on heart, eyes and swim bladder inflation seen in EtOH exposed fish. The larvae were more active in the dark than in light conditions, and EtOH reduced the swimming activity in the ELD test. EtOH affected the sleep pattern, inducing several arousal periods and increasing inactivity in zebrafish. FA reduces these toxic effects and produced more consistent inactivity during the night, reducing the arousal periods. FA also prevented the EtOH-induced defects in thigmotaxis and optomotor response of the larvae. We conclude that in this FASD model, EtOH exposure produced several teratogenic and behavioral defects, FA reduced, but did not totally prevent, these defects. Understanding of EtOH-induced behavioral defects could help to identify new therapeutic or prevention strategies for FASD.

Thyroxine, levothyroxine, and thyroxine complexed into cyclodextrin changed animal behavior, oxygen consumption, and photopic electroretinogram of Colossoma macropomum.

The toxic effects of thyroxine (T4F), levothyroxine (L-T4), and thyroxine complexed into ß-cyclodextrin (ß-CD-T4) on the biological parameters of tambaqui (Colossoma macropomum) were evaluated. The animals were exposed to a chronic toxicity test based on concentrations of influent (60 ng/L) for 2 months. Weight, total length, animal behavior, oxygen consumption, photopic electroretinogram (ERG), and the Flicker exam were evaluated. No significant differences were observed (p > 0.05) on the weight and total length measurements between all groups studied. Behavioral observations of the animals exposed to L-T4 and ß-CD-T4 complex showed a reduction (p < 0.05) in slow swimming and an increase in staying motionless events. The animals exposed to the ß-CD-T4 complex presented the highest O2 consumption. L-T4 and ß-CD-T4 promoted a reduction in the ability of the animals to respond to stimuli in the photoreceptors according to the photopic ERG examination. Data from the experimental Flicker exam showed no significant differences (p > 0.05) in all groups studied. It can be concluded that the complexation of T4 into ß-CD and L-T4 modified the toxicity of this hormone, promoting changes in the behavior, oxygen consumption, and electrophysiological responses of the exposed animals, suggesting that inclusion complexes should be submitted to new toxicity tests to ensure higher safety.

Evaluation of the toxic effect of endocrine disruptor Bisphenol A (BPA) in the acute and chronic toxicity tests with Pomacea lineata gastropod.

Bisphenol A (BPA) is a plasticizer and a risk when it interacts with organisms, and can cause changes in the development and reproduction of them. This study aimed to evaluate the effects of BPA, by acute and chronic toxicity tests with neonates and adults of Pomacea lineata. Adults and neonates were divided into groups exposed to BPA (1-20mg/L), or 17ß-estradiol (1mg/L) and control in the acute and chronic toxicity tests. Behavior, heart rate, reproduction and hemolymph biochemical analysis were measured. In the acute toxicity test, the 96-h LC50 with adults was 11.09 and with neonates was 3.14mg/L. In this test, it was observed lethargic behavior and an increase of 77.6% of aspartate aminotransferase in the adults' hemolymph (p<0.05); and neonates' heart rate decreased 72.7% (p<0.05). In the chronic toxicity test, it was observed behaviors associated with reproduction, as Copulate, in the groups exposed to BPA. The results that were found in this study proved that BPA is a potentially toxic agent to Pomacea lineata according to biological parameters evaluated. These data contribute to the understanding of BPA toxic effects' in the aquatic invertebrates.