Female zebrafish (Danio rerio) demonstrate stronger preference for established shoals over newly-formed shoals in the three-tank open-swim preference test

Enhanced behavioral assays in adult Zebrafish using an LED-based experimental tool

Animals, which serve as models in human behavior and neuroscience research, offer invaluable insights into the intricate systems that underpin our actions and cognitive processes. Among the diverse array of organisms utilized in such studies, zebrafish are particularly promising subjects for behavioral experimentation. Although various behavioral assays have been developed to analyze neurological abnormalities in adult zebrafish, including anxiety, fear responses, cognitive impairment, and social interaction deficits, these assays are limited by numerous factors, including the spatial constraints of traditional cage setups, variability in experimental techniques, and the impact of animal handling on behavioral outcomes. To address these limitations, we developed a screen-based behavioral tool featuring LED displays positioned on either side of the experimental enclosure. Subsequently, we conducted a series of behavioral analyses, including assessments of learning, social interaction, fear, and preference in adult zebrafish, using this cutting-edge behavioral apparatus. This new approach effectively alleviates spatial constraints by projecting stimuli onto a screen and standardizing the experimental conditions across multiple researchers. Moreover, the screen-based setup minimized experimenter interference within the testing environment, ensuring improved consistency and objectivity in data collection. By overcoming traditional constraints and simplifying experimental procedures, this innovative approach marks a new era in behavioral research, enabling deeper insight into the complex mechanisms of behavior and cognition.

Personality Affects Zebrafish Response to Sertraline

Sertraline is widely prescribed to treat anxiety and depression. Sertraline acts by blocking serotonin, norepinephrine, and dopamine transporters systems and has been detected in surface waters globally, where it may impact fish behavior. We classified zebrafish personality on three behavioral axes, boldness, anxiety, and sociability, assigning fish as either high or low in each category. The fish were exposed to nominal concentrations of 0, 5, 50, 500, or 5000 ng/L sertraline (measured concentrations: <10, 21.3, 370, and 2200 ng/L, respectively) to assess changes in boldness, anxiety, and sociability after 7 and 28 days. We also measured shoaling behavior and response to an alarm cue, and determined the gut microbiome of a subset of fish. After 7 days there was no overall effect of sertraline on boldness, but there was an interaction between initial personality and sex, with a stronger impact on females classified as low-boldness personality. Sertraline reduced sociability in all treatments compared with the control, but there was again an interaction between sertraline and initial personality. Fish that were classified as low-sociability responded more strongly to sertraline. After 7 days, fish exposed to a nominal concentration of 5000 ng/L (2200 ng/L measured) showed higher anxiety than controls, with the overall pattern of initial behavior retained. After 28 days, similar patterns were observed, but with higher variation. There was only a weak association between the gut microbiome and personality. Overall, the study highlights the importance of considering initial behavior, which can affect response to pollutants. Our results may also be applicable to human studies and provide a mechanism to explain why different individuals respond differently to the drug. Environ Toxicol Chem 2024;43:132-146. © 2023 SETAC.