Nature 261, 583 - 585 (17 June 1976); doi:10.1038/261583a0

In vivo evidence for a circadian rhythm in membranes of Gonyaulax

MARINA ADAMICH, PHILIP C. LARIS & BEATRICE M. SWEENEY

Department of Biological Sciences, University of California, Santa Barbara, Santa Barbara, California 93106

IT has been suggested that rhythmic oscillations in membranes are the underlying mechanism for endogenous circadian rhythms^1,2 To support this suggestion, periodic oscillations in membranes of organisms displaying circadian rhythmicity must first be demonstrated. Rhythmic oscillations associated with membranes have been observed in the spontaneous firing of the optic nerve of Aplysia ³ and in the transmembrane potential of the pulvini of Samanea ⁴. It is not clear if these membrane-associated rhythms are a function of specialised cells, or are basic phenomena of circadian rhythms. The only membrane-associated rhythm described in a unicellular organism so far is that of a circadian rhythm in particle distribution of one of the membranes of Gonyaulax polyedra ⁵. We have now investigated the rhythmic changes in the membrane potential of G. polyedra. We used the method of Hoffman and Laris⁶, in which fluorescent cyanine dyes are used to monitor the membrane potential in vivo of cells not amenable to the insertion of microelectrodes, in this case because of their small size and lack of a central vacuole. Our results suggest a temporal reorganisation of one of the membranes of Gonyaulax with circadian time.

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