Biology session

Zebrafish (Danio rerio) have numerous prominent characteristics that make them an ideal vertebrate model organism for neurobehavioral and ecotoxicological research. These include a relatively small body size and short generation time. Furthermore, their embryos are transparent that develop ex utero from the fertilized eggs. Recent studies have provided an excellent insight into the use of larval zebrafish for measuring locomotor activity. Adult zebrafish are highly social animals and have the tendency to form tight groups called shoals. Shoaling behaviour is an important behaviour paradigm, with the help of which we can better understand human neurological diseases and the effects of chemical substances (e.g. ethanol) on the development and biological mechanisms of behaviour disorders of the brain.

The aim of our study was to test a new measuring system that enables the monitoring and analysation of the species’ group cohesion (social interaction) in different sex and density groups. We tested group cohesion both in the absence (control) and in the presence (0.5%; 1.0%) of ethanol. We used Komi program for monitoring and each recording lasted for 2 minutes. The most important parameter that characterized the social interaction of zebrafish was the total area of the bounding polygon around the fish. The distances measured from the closest and the farthest neighbour were also calculated, thus we could model group cohesion.

The distance between the individuals of the male, female and mixed-gender groups was different in the same density but disparate sex groups. There was also a distinction between juveniles (1 to 3 months) and adults. The concentration (0.0% control, 0.5%, 1.0%) of ethanol also had an impact on the formation of group cohesion. For instance, exposure to 1.0% ethanol for 60 minutes inhibited shoaling. We conclude that this new behaviour analyser is appropriate for measuring the group cohesion (social interaction) of zebrafish. We managed to test this new system and program successfully. During the experiments we could establish a quantitative evaluation of the group cohesion created by the different age and sex groups. Furthermore, we could model the disintegration of the groups with the apply of a reference compound.