They are also a shoaling species, which means they prefer to group together. Dr Brennan and her team predicted that the environment they were kept in would affect their stress levels and, therefore, their response in the tank diving procedure.
They tested various aspects of how the fish were housed in a series of experiments. Some were kept in large groups, some in pairs; some were allowed only visual contact with other fish and some only could only smell each other.
They found that individually housed fish spent less time on the bottom of the tank compared to their group housed colleagues.
The team also studied how the fish reacted to ethanol, which is known to have an anti-anxiety effect on zebra fish. Their results showed that fish kept on their own responded to the ethanol, but those in a group did not.
In a third experiment, the team tested the levels of cortisol - a common hormone produced when animals are under stress - of both the group and individually housed fish, and found that individually housed fish had lower levels.
In their final experiment, they examined the effects of changing the fishes' water prior to tank diving. It had no effect on individually housed fish, but appeared to affect the typical tank diving responses of the group housed individuals.
Dr Brennan believes that the way in which the zebrafish are housed plays an important factor in obtaining reliable data from tests like this, and should be considered by researchers interested in comparative models of anxiety or indeed any behavioural test in zebrafish in order to refine their approach and increase experimental power.
She adds: "Not only will publication of our results improve the reliability of zebrafish behavioural analysis, but, by demonstrating that by refining housing one can increase the power of our analysis and reduce the number of animals used, we contribute to the 3Rs aim of UK and international science poli
|Contact: Bridget Dempsey|
Queen Mary, University of London