What do male and female zebrafish prefer? Directional and colour preference in maze tasks

Studies regarding the animals' innate preferences help elucidate and avoid probable sources of bias and serve as a reference to improve and develop new behavioural tasks. In zebrafish research, data obtained in behavioural assessments are often not replicated between research groups or even inside the same laboratory raising huge concerns about replicability and reproducibility. Among the potential causes that are not well considered, sexual differences can be a probable source of bias. Thus, this study aimed to investigate the male and female zebrafish directional and colour preferences in the plus-maze and T-maze behavioural tasks. Experiment 1 evaluated directional preference, and experiment 2 evaluated colour preference in a plus-maze task; experiment 3 evaluated preference between black or white in a T-maze task. Individual preferences were expressed as the percentage of time spent in each zone. Our results showed that male and female zebrafish demonstrated no difference in directional preference in the plus-maze task. Surprisingly, male and female zebrafish showed colour preference differences in the plus-maze task; males did not show any colour preference, while female zebrafish demonstrated a red preference compared to white, blue and yellow colours. Moreover, both male and female zebrafish demonstrated a strong black colour preference compared to the white colour in the T-maze task. Our findings characterized the spontaneous preference of male and female zebrafish for direction and colour, identifying possible biases and providing insights that contribute to the standardization of future protocols.