Waterborne agrichemicals compromise the anti-predatory behavior of zebrafish.

Due to human activities, there is an increasing presence of agrochemicals residues in water bodies, which could be attributed to an increased use of these chemicals, incorrect disposal of packaging materials, and crop leaching. The effects of these residues on prey-predator relationship of aquatic animals are poorly known. Here, we show that fish acutely exposed to glyphosate, 2,4-D, and methylbenzoate-based agrichemicals have their anti-predatory responses impaired. We exposed zebrafish to sub-lethal concentrations of agrichemicals and evaluated their behavioral reaction against a simulated bird predatory strike. We observed that agrichemical-exposed fish spent more time in a risky area, suggesting that the pesticides interfered with their ability of risk perception. Our results highlight the impairment and environmental consequences of agrochemical residues, which can affect aquatic life and crucial elements for life (food web) such as the prey-predator relationship.

Aripiprazole prevents stress-induced anxiety and social impairment, but impairs antipredatory behavior in zebrafish.

Environmental pollution caused by antipsychotic residues is a relevant ecological problem. Studies revealed that residues of these drugs are present in a wide range of different ecosystems and can have adverse effects on non-target organisms even in low environmental concentrations. Among these antipsychotic drugs, aripiprazole (APPZ) is a second-generation atypical antipsychotic that is a partial agonist of dopaminergic and serotoninergic receptors. APPZ is used to treat schizophrenia, bipolar disorder, autism, obsessive-compulsive disorder, and anxiety or panic disorders. Thus, in this study we posed the following question: "What will be the behavioral effects of waterborne APPZ on fish?" To answer this question, we exposed adult zebrafish to different APPZ concentrations (0.556, 5.56, and 556 ng/L) for 15 min and evaluated their exploratory, anxiety-like, social, and anti-predatory behaviors. Our results showed that, despite the apparent beneficial reversal of stress-induced social impairment and anxiety-like behavior, APPZ exposure impaired the anti-predatory reaction of adult zebrafish. Taken altogether, our results show that APPZ-exposed zebrafish may have a decreased perception of predators, even at concentrations lower than those already detected in the environment. A failure to exhibit an antipredatory response may favor the predator, decrease the fitness of the prey species, and, consequently, affect the food chain. Our results highlight the risks and consequences associated with APPZ residues in water, which may affect aquatic life and endanger species that depend on appropriate behavioral responses for survival.

Persistent and transgenerational effects of risperidone in zebrafish.

Since behavior is the connection between the internal physiological processes of an animal and its interaction with the environment, a complete behavioral repertoire is crucial for fish survival and fitness, at both the individual and population levels. Thus, unintended exposure of non-target organisms to antipsychotic residues in the environment can impact their normal behavior, and some of these behavioral changes can be seen during the entire life of the animal and passed to subsequent generations. Although there are some reports related to transgenerational toxicology, little is known of the long-term consequences of exposure to pharmaceutical compounds such as risperidone. Here, we show that zebrafish exposed to risperidone (RISP) during embryonic and larval stages presented impaired anti-predatory behavior during adulthood, characterizing a persistent effect. We also show that some of these behavioral changes are present in the following generation, characterizing a transgenerational effect. This suggests that even short exposures to environmentally relevant concentrations, at essential stages of development, can persist throughout the whole life of the zebrafish, including its offspring. From an environmental perspective, our results suggested possible risks and long-term consequences associated with drug residues in water, which can affect aquatic life and endanger species that depend on appropriate behavioral responses for survival.

Modulation of Cortisol Responses to an Acute Stressor in Zebrafish Visually Exposed to Heterospecific Fish During Development.

Studies regarding predator-prey relationships have often focused on prey assessment and the responses to predation risk, but few have verified the relationship in the presence or absence of visual contact with a predator (e.g., tiger oscar, Astronotus ocellatus) or a nonpredator (e.g., goldfish, Carassius auratus) during the developmental phase, which could alter several physiological and neuroendocrine mechanisms in adulthood. Herein, we determined responses to physical (chasing with a net) and biological stressors (visualization to predator) in adult zebrafish raised in visual contact with a predator or nonpredator fish. We demonstrated that adult naive zebrafish show a more intense cortisol stress response than fish housed in visual contact with the stimulus fish (predator or nonpredator) when larvae, and that this alteration is related with movement specificity of the stimulus fish.

Alterations on piscivorous diet following change in abundance of prey after impoundment in a Neotropical river

The goal of this study was to investigate the alterations of diet of a piscivorous fish (Acestrorhynchus pantaneiro) following changes in abundance of a forage fish (Moenkhausia dichroura) during the trophic upsurge stage in a reservoir. Fish samplings were taken monthly in the Manso Reservoir (State of Mato Grosso, Brazil) from March 2000 to February 2001 (period I) and from March 2003 to February 2004 (period II). The abundance of Moenkhausia dichroura in the reservoir was significantly different in both periods, representing 9.6% of the individuals in period I and 66.4% in period II. Stomach contents analyses showed that the number of prey species consumed by A. pantaneiro decreased from 41 prey in period I to 14 in period II. In the last period M. dichroura was the most important prey, comprising 95% of the diet, in contrast with the period I when this species represented only 15% of the diet. The predator and prey size relationship was positive in both periods, however was significantly different, because small and large predators consumed mainly small prey (M. dichroura) in period II. Thus, the results showed that A. pantaneiro altered its diet composition, trophic niche breadth and prey sizes to feed on more abundant and accessible prey. These alterations probably caused a decrease in energy costs related to prey searching, maximizing the energy gain of the predator.

O objetivo deste estudo foi investigar alterações na dieta de um peixe piscívoro (Acestrorhynchus pantaneiro) após mudanças na abundância de um peixe forrageiro (Moenkhausia dichroura) durante a colonização de um reservatório. Os peixes foram amostrados mensalmente entre março/2000 e fevereiro/2001 (período I) e março/2003 e fevereiro/2004 (período II), no reservatório de Manso (Mato Grosso, Brasil). A abundância de M. dichroura foi significativamente diferente entre os períodos, representando 9,6% dos indivíduos no período I e 66,4% no período II. No período I A. pantaneiro consumiu 41 presas, enquanto que no período II foram registradas 14 presas, sendo que M. dichroura foi a presa mais consumida, passando a representar 95% da dieta, enquanto no período I representava apenas 15%. A relação entre o tamanho do predador e da presa foi positiva em ambos os períodos, porém significativamente diferente. No período II pequenos e grandes predadores consumiram principalmente pequenas presas (M. dichroura). Os resultados mostraram que A. pantaneiro consumiu, no período II, a presa mais abundante e disponível, alterando a composição de sua dieta, amplitude do nicho alimentar e tamanho da presa. Estas alterações provavelmente causaram um decréscimonos custos energéticos associados à procura da presa, maximizando o ganho de energia do predador.