2000 Volume 13 Issue 1 Pages 27-32
Postural control in fish is mainly regulated by vestibular information under normal gravity conditions (1G). The aim of this study is to compare the ability of gravity sensations (i. e., vestibular function) in a food fish maintained at a lunar base or in a centrifuge rotor under microgravity. This experiment was conducted at low gravity (0.05G, 0.1G, and 0.2G) and under microgravity conditions to observe changes in the swimming behavior of juvenile tilapia, Oreochromis niloticus (TL 3-4cm) using a parabolic flight of an aircraft. The swimming behavior of the fish was similar under microgravity and at 0.05G conditions, indicating that their postural control depends on dorsal light response (i. e., visual information) rather than vestibular function. At 0.1G conditions about 40% of the fish showed normal swimming behavior when the direction of the light and gravity were same, demonstrating that both factors were helping the fish in controlling their posture. In contrast, 80% of the fish were oriented perpendicular to the direction of gravity, independent of the light direction under 0.2G condition. These results suggest that tilapia can sense gravity around 0.1G and their postural control depends on vestibular information at 0.2G.
