Wall following inXenopus laevisis passive

Abstract

2 1 2 2Summary statement: Xenopus laevis tadpoles and froglets tend to swim along the walls of a square tank; but this 2 3 wall following is passive -in a convex tank, they leave the wall. 2 4 2 5 2 6 2 Abstract 2 7The tendency of animals to follow boundaries within their environment can serve as a strategy for spatial learning or 2 8 defence. We examined whether animals of Xenopus laevis employ such a strategy by characterizing their swimming 2 9behaviour. We also investigated potential developmental changes, the influence of tentacles, which some of the 3 0 developmental stages possess, and whether wall-following is active (animals seek out wall contact) or passive. 1Animals' swimming movements were recorded with a camera from above in a square tank with shallow water and 3 2 their trajectories were analysed especially for proximity to the nearest wall. With the exception of young larvae, in 3 3 which wall following was less strong, the vast majority of animals -tadpoles and froglets -spent more time near the 3 4wall than what would be expected from the proportion of the area near the wall. The total distance covered was not a 3 5 confounding factor. Wall following was also not influenced by whether the surrounding of the tank was black or 3 6 white, illuminated by infrared light, or by the presence or absence of tentacles. Animals were stronger wall followers 3 7 in smaller tanks. When given a choice in a convex tank to swim straight and leave the wall or turn to follow the wall, 3 8 the animals consistently left the wall, indicating that wall following in Xenopus laevis is passive. This implies that 3 9 wall following behaviour in Xenopus derives from constraints imposed by the environment (or the experimenter) 4 0 and is unlikely a strategy for spatial learning or safety-seeking. 4 1