LCD画面による縞状パターン移動照射に対するメダカの行動変容と行動制御の可能性

<p>In this study, we tried to control the behavior of Medaka (Japanese Killifish) by applying their phototaxis. First, we investigated Medaka’s general phototaxis by irradiating the light of the LCD display to a portion of the pool. We examined various lighting patterns such like half portion irradiation, center irradiation, peripheral irradiation, gradation pattern irradiation, etc. We recorded the Medaka’s swimming path and analyzed the abundance ratio by brightness. Medaka, however, did not show the typical positive/negative phototaxis to the LCD display light clearly. Medaka showed negative phototaxis to the irradiation of the strong light over 20,000 lx. Therefore, the irradiation of strong light is necessary to control Medaka’s behavior by general phototaxis. On the other hand, however, Medaka showed typical reaction patterns to the flow movies of the black/white stripe irradiated by LCD display. When Medaka showed these stripe flow patterns, (1) Medaka always tried to get on and follow the stripe flow, (2) Medaka stopped swimming when the pool wall would approach, Medaka never contact the wall, (3) Medaka turned to the backflow direction, (4) Medaka swam to the upstream side with slower speed and intermittent swimming. (5) Medaka turned to the flow direction again then back to (1). The medaka seemed to misunderstand that there was actually a stream of water. We call this reaction pattern of Medaka “Stripe flow phototaxis”. The stripe condition that Medaka showed typical reaction is that the stripe width is near the body length of Medaka, and the flow speed is about the half of the Medaka’s maximum swimming speed. We found Medaka can be controlled their behaviors by showing the stripe flow to the desired direction.</p>