Shoaling, boldness, anxiety-like behavior and locomotion in zebrafish (Danio rerio) are altered by acute benzo[a]pyrene exposure.

Environmental exposure to crude oil and/or its derivatives in fishes can negatively impact survival, morphology and physiology, but relatively little focus has been on behavior. Exposures can influence prey-predator interactions, courtship and other vital behaviors, leading to individual or population disruption at toxicant levels well below those producing morphological or physiological changes. The few behavioral studies of polycyclic aromatic hydrocarbons (PAHs) on fish behavior have yielded highly inconsistent results, likely relating to chronic vs. acute treatment. A few studies report lethargy and decreased exploratory behavior, while others indicate increased anxiety and greater exploratory behavior with PAH exposure. In our study on zebrafish (Danio rerio), we hypothesized that even relatively brief (30 min) exposure to the PAH benzo[a]pyrene (B[a]P) would impact group shoaling and individual behaviors in open field and novel object exploration tests. Exposures comprised measured concentrations of 1.0 μM, 10 μM, or 100 μM, B[a]P. Compared to controls, inter-individual distance (IID) was significantly increased by 100 μM B[a]P, but not by 1.0 μM or 10 μM B[a]P. Total distance moved by shoals was decreased significantly at B[a]P concentrations of 1.0 μM, 10 μM and 100 μM. In the open field test of individual locomotion and anxiety-like behavior, time spent in the thigmotaxis zone along the walls of the circular test arena (a proxy for anxiety-like behavior), was decreased at 100 μM. In the novel object approach test to investigate boldness, time spent near the object was significantly increased by both 10 μM and 100 μM B[a]P. Collectively, these data indicate a complex suite of changes in zebrafish including altered shoal dynamics, decreased anxiety, increased boldness, and decreased locomotion associated with exposure to B[a]P.