Efeito do tempo de alojamento em grupos de diferentes densidades sobre a ansiedade em Danio rerio

Abstract

The physiological and behavioral effects of animal agglomeration or isolation have been studied extensively, either in models for psychopathological studies or even to identify possible consequences for data collection in scientific research. In sociable species such as Danio rerio, variation in lodging density represents a relevant variable that needs to be considered. Thus in this study we evaluated the effects of lodging at different densities per liter, for different exposure times, on the anxiety response measured in the Light/Dark preference test, Predator Inspection Test and Plus Maze with Ramp in Danio fish. Fishes of the species Danio rerio (216) were divided into 3 large groups according to Time of lodging (1, 7 and 30 days), each group was divided into 6 subgroups according to Density of fish (0,25, 0, 5, 1, 2, 4, 6 fish/liter) and housed in a 4 liter aquarium (n = 8). The 16 and 24 groups were filled with D. rerio confederates who were not tested but who remained in the aquarium to make up the population. After the lodging conditions each animal was tested in the protocols: Light/Dark Preference (CE), Predator Inspection (IP) and Plus Maze with Ramp (PMR). The lodging conditions altered the exploratory behavior of the subjects in the three protocols. In CE the time of lodging intensified the effects of agglomeration and reduced the motor activity in groups housed at densities of 2 and 6 fish/liter. In the IP tests Density reduced the number of crosses between quadrants in the 24-subject group, and increased the time of animals inspecting the predator. In the Plus Maze with Ramp Time and Density altered the behavior of the apparatus, the groups with 2 and 6 subjects reduced the exploration of the ramp arms and increased in the flat arms, in counterpart the isolation increased the exploration of the ramp arms. In this study we showed that conditions of lodging can act as low-intensity chronic stressors that alter anxiety-type behavior in zebrafish when tested in Light/Dark and Plus Maze with Ramp protocols and fear-type behavior when exposed to the Predator Inspection test.