Increase in environmental temperature affects exploratory behaviour, anxiety and social preference in Danio rerio

Abstract

The aim of this work is to investigate the effect of a temperature increase on the behaviour of adult zebrafish (Danio rerio) maintained for 21 days at 34 °C (treatment) and 26 °C (control). The temperatures chosen are within the vital range of zebrafish and correspond to temperatures that this species encounters in the natural environment. Previous results showed that the same treatment affects the brain proteome and the behaviour of adult zebrafish by producing alterations in the proteins involved in neurotransmitter release and synaptic function and impairing fish exploratory behaviour. In this study, we have investigated the performance of treated and control zebrafish during environmental exploration by using four behavioural tests (novel tank diving, light and dark preference, social preference and mirror biting) that are paradigms for assessing the state of anxiety, boldness, social preference and aggressive behaviour, respectively. The results showed that heat treatment reduces anxiety and increases the boldness of zebrafish, which spent more time in potentially dangerous areas of the tank such as the top and the uncovered bright area and at a distance from the social group, thus decreasing protection for the zebrafish. These data suggest that the increase in ambient temperature may compromise zebrafish survival rate in the natural environment.

Acute environmental temperature variation affects brain protein expression, anxiety and explorative behaviour in adult zebrafish

“…3 l) could reflect the reduced swimming activity of fish at low temperature. By contrast, 21-d chronic exposure at 34 °C showed a reduction in the time and distance spent in the social area 56 . This result suggests that the stress condition induced by 4-d heat treatment at 34 °C does not alter the interest in conspecifics; however, prolonged exposure to the same temperature for three weeks causes an alteration of the social interaction.…”

“…Behavioural tests were conducted using the same apparatus and protocol used in our previous studies to which reference is made for details (YMT 14 and NTT, LDT, SPT, MBT 56 ).…”

“…To reduce stress on individuals and to allow comparisons with behavioural results previously obtained after a 21-day chronic thermal treatment 14 , 56 , we decided to use 15 individuals exclusively for the YMT test and 15 individuals for LDT, NTT, SPT and MBT. The number of experimental subjects was chosen, given the reduction criteria, on the basis of data in the literature suggesting that in zebrafish, significant data may be obtained with n = 12–15 per group for strong effects 40 .…”

“…Previous research from our group investigated the effect of chronic exposure (21 d) to the same temperatures of 18 °C, 26 °C and 34 °C on adult zebrafish 14 , 56 . The three temperature values were chosen according to Vergauwen et al 49 within the zebrafish vital range and correspond to temperatures the fish cope with in the natural environment.…”

“…In particular, we found that reduced expression of synaptic proteins and downregulated protein pathways were positively correlated with impairments of the cognitive abilities of fish in the Y-Maze test. In addition, behavioural tests showed that long exposure to 34 °C reduces the anxiety-like status of zebrafish 56 .…”