Pez-cebra (Danio rerio) como modelo de bienestar animal

Abstract

Zebrafish has become an important model for various disciplines such as neuroscience and the testing of new pharmacological molecules. Therefore, the way in which it is housed and the consequences of its accommodation on its well-being represent an important aspect to study. Very few studies have evaluated the effect of environmental enrichment on the welfare of zebrafish and its negative or positive impacts have yet to be elucidated. An important challenge is to establish the consequences not only of the presence of enrichment but also of its loss. Likewise, the form of presentation of a stimulus, either predictably or unpredictably, influences the physiological and behavioural responses of the animal. Therefore, the form of presentation of the enrichment represents another important aspect to assess. The evaluation of emotional (affective) states is crucial for the study of zebrafish welfare, in particular to evaluate the influences of the environment on the animal. However, directly assessing these states is difficult due to their subjective nature. Therefore, the current approach focuses on estimating them from the resulting physiological and behavioral components. Today there are robust standardized tests that assess and correlate neuroendocrine responses with well-established behavioural assessment criteria for stress and anxiety in zebrafish. However, there are no similar tests to measure positive emotional states in this species. An alternative metric to assess both the positive and negative affective states of animals is the cognitive bias. These tests allow researchers to infer an individual's emotional state from cognition. Therefore, the evaluation of apparently negative (Unpredictable conditions and absence or loss of enrichment) and positive ones (Predictable conditions and presence or gain of enrichment) accommodation contrasts through a type of cognitive bias (cognitive judgment bias (CJB) in zebrafish may constitute a promising model to understand the effects of housing on affective states and well-being in this fish. Additionally, it has been shown that individual variations such as personality influence the central nervous system, behaviour and cognitive judgment bias results in other species. These differences and their impacts on zebrafish have not yet been studied. Consequently, the general objective of this thesis was to establish if the cognitive judgment bias can be used in zebrafish for the evaluation of positive and negative emotional states produced by environmental modifications and its relationship with personality.