O que há por trás das diferenças individuais? Perfis comportamentais e fisiológicos em Betta splendens

Abstract

According to environmental changes, the individuals show different strategies to coping with the varied external stimuli. The different responders comprise the different phenotypes that compose a population. These differences can be explained by endogenous changes, such as hormonal secretion. For instance, hormones modulate reproductive behaviors and cognitive processes. In order to characterize individual differences in a population, the present study aimed to testing the relationship between behavioral and hormonal profiles in a group of males Fighting fish, Betta splendens. A group of 86 males were observed for bubble nest construction, agonistic displays in conspecific contests and performance in a spatial learning protocol. After that, cortisol and testosterone plasma levels were measured. An innovative and stylish statistical procedure was applied to the data set in order to separate animal in groups related to its nest building behavior (k-means test) and then shown which behavioral and physiological parameters better explain the groups’ profiles (Random forest and Classification tree). Our results point to three distinct profiles: nest builders (nests of 30.74 ± 9.84 cm²), intermediates (nests of 13.57 ± 4.23 cm²) and non-builders (nests of 2.17 ± 2.25 cm²). These groups presented marked different in agonistic and learning behavior, as well as hormone levels. Cortisol was the main predictor prepared by the Random Forest test for the separation of individuals in the different groups: nest builders and intermediates showed lower levels of cortisol while non-builders presented the highest basal cortisol values. The second most important predictor was learning performance, that separated animals from the intermediate from the nest builders (faster learners), followed by basal testosterone levels and agonistic behavior displays. While the testosterone levels were not significant to explain behavioral differences, it seems to be related to the construction profile. Our finding shows that different profiles invest differently in reproduction and that cortisol negatively influences nesting behavior and learning. In summary, our data suggest that different profiles in a population are determined by both hormonal and behavioral responses, and these differences confer flexibility to the population, allowing the presence of animals that invest the most in reproduction while other show defense and aggression as the dominant feature expressed.