單眼在美洲蟑螂避光行為的角色

Abstract

美洲蟑螂 (Periplaneta americana) 為夜行性昆蟲，具有二個複眼和二個單眼，強光剌激會激發蟑螂產生避光的逃跑行為。本研究利用自行研發設計的紅外光閘結合自動記錄裝置，以量化蟑螂避光反應的反應時間 (reaction time) 及運動速率，比較切除蟑螂複眼或單眼對其避光行為的影響。結果證明切除兩個複眼時，蟑螂完全喪失避光行為，但只切除兩個單眼時，強光誘發蟑螂逃跑的反應顯著變慢，而且逃跑的運動速率也顯著變快，但是遇暗停止反應 (shade response) 會延遲。此一結果證明複眼對蟑螂的避光行為有決定性的影響，而單眼也具有調節性的效應，單眼的訊息和複眼同樣有效，可以影響調控避光行為的相關中樞。

The American cockroach Periplaneta americana is a nocturnal insect having two compound eyes and two ocelli. The light-avoiding response of cockroach is always induced by illumination. In order to investigate the role of ocelli in the light–avoiding response of cockroach, we have occluded the ocelli or compound eyes to block the visual signals and measured quantitatively the light-avoiding response by using an infrared detector. We found that the light-avoiding response disappeared by occluding compound eyes, however, the reaction time of the treated groups (ocellar occlusion) were significantly longer than that of control groups. Furthermore, the speed of the treated groups through the infrared detector was always faster than that of the control groups. These results suggest the existence of parallel pathways each convening information from illumination of compound eyes and ocelli that would converge in the same higher center.