Role of the sinus gland in crayfish circadian rhythmicity—II. ERG circadian rhythm

Abstract

1. 1. The periodical release of sinus gland neurosecretions and the role of the sinus gland in the generation and maintenance of the circadian rhythm of the crayfish electroretinogram (ERG) were studied in isolated eyestalks and intact and surgically ablated animals. 2. 2. Eyestalk extracts were prepared at different circadian times (CT) and injected into isolated eyestalks. The ERG from the isolated eyestalks was recorded before and after extract injection. 3. 3. ERGs from both eyes of intact animals and animals with one or both sinus glands removed were recorded continuously for at least 7 days. 4. 4. The ERGs from isolated eyestalks that had been exposed to extract showed changes in the amplitude of the rhythm that were dependent on the CT of the preparation of the extracts. 5. 5. The ERG rhythms of intact animals were always in synchrony. In animals with one sinus gland removed, the ERG of the operated eye showed modifications in both amplitude and period and was desynchronized with respect to the intact eye, whose ERG rhythm was normal. After bilateral gland excision, both eyes showed amplitude and period variations of the ERG, which was also desynchronized. 6. 6. The results suggest that the sinus gland is a circadian oscillator participating in the multioscillator system that generates and maintains the ERG circadian rhythm.