Effects of pinealectomy and bilateral enucleation on the phototactic response and on the conditioned response to light of the goldfish Carassius auratus L.

Abstract

Intact goldfish in a light gradient were unevenly distributed and spent most of their time in the darker half of the gradient. Pinealectomized, bilaterally enucleated, or pinealectomized plus bilaterally enucleated goldfish were distributed uniformly throughout the light gradient. It was concluded that the phototactic response of goldfish depends upon the presence of the pineal organ as well as the eyes.In a conditioning situation, pinealectomized animals with intact vision showed significantly more responses to the conditioned stimulus than did the control animals with intact vision when the conditioned stimulus was light, but not when the conditioned stimulus was sound. Blind goldfish, with or without an intact pineal, could not be effectively conditioned to light although they did become conditioned to sound. Pinealectomy did not affect the conditioning of either the blind or the eyed goldfish to sound.Among goldfish with intact vision, pinealectomy increased the spontaneous swimming activity. Blinding enhanced the level of spontaneous swimming activity more than did pinealectomy. But blind plus pinealectomized goldfish displayed a level of spontaneous swimming activity which was intermediate between the level shown by pinealectomized eyed animals and blind animals with an intact pineal.The significance of these findings has been discussed in terms of the photosensory role of the goldfish pineal organ.