New findings by researchers at the New York University Polytechnic School of Engineering are helping to unravel the complex interplay between alcohol and social behaviour and may lead to new therapies for mitigating the negative impacts of alcohol use and abuse.
A team led by Maurizio Porfiri devised an original method that would allow for detailed tracking of a single, alcohol-exposed zebrafish amid a school of "sober" peers.
The research team posited that an individual's response to alcohol would vary based on the presence or absence of unexposed peers.
What they did not anticipate, however, was the remarkable effect the alcohol-exposed fish would have on unexposed shoalmates.
Porfiri and his colleagues designed an experimental procedure in which a single zebrafish was exposed to four concentrations of ethanol in water, ranging from zero to high.
Following exposure, the fish was released into a group of untreated zebrafish.
A custom tracking algorithm allowed the researchers to follow for the first time individual fish throughout the experiment as well as analyse group behaviour.
Previous studies show alcohol exposure affects zebrafish locomotion - at low concentrations, fish tend to swim faster, and as the dose increases, swimming typically slows. Alcohol can also negatively impact the school's cohesion.
In Porfiri's trials, the single exposed zebrafish showed changes in locomotion when observed alone consistent to those predicted by independent studies in the past.
In a group setting, however, the zebrafish behaviour was remarkably different: Fish exposed to intermediate or high alcohol concentrations nearly doubled their swimming speeds, suggesting that the presence of peers had a substantial impact on social behaviour under the influence of alcohol.
Most remarkably, the unexposed fish also modulated their behaviour and swimming speeds differentially in the presence of a shoalmate exposed to different levels of alcohol.
"These results were very surprising. It is clear that the untreated fish were matching the swimming speed of the alcohol-exposed fish, and this correlation was especially strong at an intermediate level of alcohol exposure. At very high or low levels, the influence decreases," said Porfiri.
Porfiri believes that one explanation for the high-speed swimming of the exposed individual may be hyper-reactivity to an enriched environment - the tank containing shoalmates.