Studies on the optomotor reaction of fishes : I. Examination of the conditions necessary to induce the reaction of the Japanese killfish, Oryzias latipes TEMMINCK et SCHLEGEL

Some experiments of the optomotor reaction using the Japanese killifish, Oryzias latipes TEMMINCK et SCHLEGEL, were carried out in the apparatus slightly modified from the one used by CRONL Y -DILLON and MUNTZ (1965) consisting in rotating pattern of alternating light and dark stripes around the glass vessel in which fish are held. The results obtained can be summarized as follows.

1. Wild fish do not show any clear positive optomotor reaction until they are well trained by 3 to 5 trial experiments. It takes 30 to 60 seconds even for welltrained fish to come to the state of following completely the moving pattern of stripes.

2. Fish show irregular optomotor reaction when they are reared in a small glass container, even if they have been duly trained. Besides, when reared in a small opaque container, they begin to react several minutes later than they do when normally reared.

3. Fish that have been shown the pattern of stripes prior to the experiment begin to react to the moving pattern of stripes earlier than those which have not been shown.

4. The starting time of the optomotor reaction in fish kept in darkness (darkadapted) is delayed correlatively to the time at which the process of light adaptation begins in retinas of fish held in the working apparatus.

1. ガラス円形水槽の周囲lこ明暗の縞模様が廻転するように考案されたCRONLV-DILLON and MUNTZの装置を改良した実験装置を用い，メダカの運動視反応の発現と飼育条件の関係を調べて，次の様な結果を得た.
2. 野生のメダカは少くとも3~5 回訓練して，始めて明瞭な運動視反応を確実に現わすようになる.しかし廻転する縞模様に完全に追随する迄には30~60 秒を要する.
3. 充分に訓練したメダカでも，これをガラス容器内で飼育して置くと，その運動視反応、は極めて不規則となり，叉狭い容器内に飼育した場合には，運動視反応は遅れて現われる.
4. 更に，実験装置内で予め縞模様を見せて置くと，メダカは縞の運動開始と殆んど同時にそれを追い始める.
5. 暗い中で飼育し暗順応状態になっているメダカは，実験開始後数分経ってから運動視反応を呈するが，この反応の発現の遅れは，実験装置内lこ入れられた暗順応状態のメダカの網膜において，錐体楕円部及び色素層とが明順応状態への網膜運動を開始するのに要する時間と一致する.