Teste de aprendizagem e preferência com o uso de labirinto em peixes

Abstract

Research related to cognitive science has been the key to understanding the internal state of animals and through the maze it is possible to reliably measure the maintenance of visual and spatial information by animals. Seeking to understand the effect of different factors on the cognitive capacities of freshwater fish, two articles were carried out. The objective of the first article was to assess whether there is a difference in learning and preference between males and females of Aulonocara nyassae blue orchid. While the second article aimed to evaluate the effect of the color of the environment on the performance of tasks involving cognition in a T-maze and the effect on preference for color in a plus-maze of the fish Pangasianodon hypothalmus. The first article was divided into two experiments, in which experiment 1, the animals were submitted to the learning test by association in a T-maze. Inside the maze, a Lego® piece was placed, as a neutral stimulus, associated with pellets of food, as a positive stimulus. After 10 days of training, a visual barrier was inserted between the Lego® piece and the food, as a challenge, maintained during the last 5 days of the study. In both stages, the time spent in latency to make the first choice, which remained in the first choice, to capture the food and the number of associations were observed. In the second experiment, males and females were also subjected to a preference test in a T-maze, where each arm received a positive stimulus, shelter or food. The animals underwent 10 days of training. Subsequently, they remained 20 days without contact with the maze and after that period they returned to the maze, after being subjected to stress by exposure to air for five minutes. It was also identified the time that the animal spent in latency, to make the first choice, time in the first choice and which was the first choice made. In experiment 1, both sexes were able to learn the association between a neutral stimulus and a positive stimulus, without distinction. Over the course of the experimental days, there was a decrease in the time spent in latency and in the time spent to capture food, for both sexes. In experiment 2, regardless of sex, the animals frequented the arm with the presence of shelter more. Even after the stress challenge, the shelter visit rate was higher than the food capture rate. Article 2 was divided into two phases: Phase 1, which consisted of analyzing the behavior learned in a T-maze; and Phase 2 which evaluated whether tank color affects color preference in a plus maze. 24 specimens of P. hypothalmus that participated in both experiments were used. The experimental period was 37 days in total. The fish were housed in groups of 6 individuals, regardless of gender, in each blue, white, black or green tank. In phase 1, the animals underwent a 2-day acclimatization period to the T-maze. After this period, they went to the maze once a day for 15 consecutive days to observe behavior. Inside the labyrinth, a Lego® piece was placed at the entrance of one of the arms, chosen by lot, and at the end of the same arm a piece of PVC pipe was placed in order to provide shelter. The behaviors analyzed during the 15 minutes that the fish remained in the T-maze were: latency time; time the fish took to make the first choice; time the fish remained in the first choice; time the fish remained idle and time to use the PVC pipe as a shelter. On the last day of the T-maze test, at the end of each observation, blood was collected for hemoglobin, glucose, cholesterol and lactate analysis. In phase 2, the fish underwent a 2-day acclimatization period to the plus maze. After this period, they went to the maze once a day for 8 consecutive days. The arms of the maze were coated with opaque paper in blue, white, green or black. The fish were allowed to swim freely in the maze for 15 minutes. During this period, the time and frequency of visitation in each arm of the maze was evaluated. The color of the environment in which it was housed had an effect on the behavior of the fish in the T-maze and on the level of blood lactate. In the plus maze P. hypothalmus showed a preference for the green color. We conclude that males and females of A. nyassae blue orchid were able to learn the task of object and food association and that learning is maintained in a challenging condition. Both sexes also prefer shelter to food even after exposure to stress. Regarding article 2, we concluded that the color of the environment interferes with the learning behavior and preference in the labyrinth of the fish P. hypothalmus.