In news you never knew you wanted to know, drunk zebrafish behave differently around sober members of their own species to when swimming alone. Moreover, the fish that have not consumed alcohol take their lead from a carousing friend.
Getting fish drunk is a thing in science. Although William Hartston's book The Drunken Goldfish is subtitled "A Celebration of Irrelevant Research" there are reasons that go beyond biologists hitting the turps themselves and suddenly slurring, “Hey how's about we get one for the lab fishies?” On the other hand, that probably happens as well.
Human responses to alcohol are mixed up with our social expectations, so that sometimes we act drunker if we think there is ethanol in our drinks than if there actually is. To study the biological effects alone we need to look at animals, and fish are actually a good model, since you can control their intake by dosing their water with a small concentration of ethanol. The study that gave Harston's book its name revealed that animals have contextual learning just like humans – what they learn when drunk they are inclined to forget when sober but remember again when re-exposed to alcohol.
It seems this is not the only way that piscine responses to getting pissed resemble those of humans. In Alcoholism: Clinical & Experimental Research a team from the New York University Polytechnic found that drunk zebrafish like to show off to the rest of the school by swimming really fast.
A team led by Associate Professor Maurizio Porfiri exposed zebrafish to ethanol in their water. They weren't the first to do this, and as others have found fish swim faster when the alcohol concentration is low than if there is none at all. However, after a certain point increasing the dose causes the fish to slow down. Moreover, when you get a whole school of fish drunk at once they start to lose their capacity to stick together.
However, Porfiri also did something new. He got one zebrafish drunk and then mixed it in with others who may have wondered what was going on with their friend. He found when the inebriated individual was given an intermediate or high alcohol concentration it responded by swimming nearly twice as fast as normal, probably thinking how impressed all its friends would be.
This had an effect on the rest of the school. “These results were very surprising,” explains Porfiri. “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.” Interestingly, while the sober fish matched their inebriated fellow for speed, they were able to maintain cohesion in a way groups of fish cannot when all are exposed to alcohol together.
Ponfiri says alcohol is known to decrease inhibitions in fish, just as it does in humans, and the faster speed may reflect a greater enthusiasm to interact with the other fish. Harder to explain is why these fish sped up as well. The research team noted that aggressive risk-taking behavior in zebrafish tends to be imitated by others and that unwise activity under the influence of alcohol may be acting as a form of leadership. We can hear the groans of recognition from highschool teachers and parents of teenagers across the planet.
Zebrafish all tend to look alike, so the study relied on new techniques for tracking the movement of a single fish in the school.
The work opens up new paths for studying the way alcohol affects human behavior in groups, but anyone thinking of tipping a bottle of vodka into their aquarium should be aware that fish are quite sensitive to alcohol concentrations, and too much can be fatal.