The Journal of Cell Biology, Vol 68, 451-461, Copyright © 1976 by The Rockefeller University Press
Freeze-fracture studies of the thecal membranes of Gonyaulax polyedra: circadian changes in the particles of one membrane face
BM Sweeney
Intramembrane faces were visualized in the marine dinoflagellate Gonyaulax
polyedra by the freeze-fracture technique, in order to test a prediction of
a membrane model for circadian oscillations--i.e;, that membrane particle
distribution and size change with time in the circadian cycle. Cells from
each of four cell suspensions in continuous light (500 1x, 20-21 degrees C)
were frozen, without fixation or cryoprotection, at four circadian times in
a cycle. This paper reports findings concerning the membranes associated
with the theca, particularly the cytoplasmic membrane and the membrane of
the large peripheral vesicle. While the number and size distribution of the
particles of the PF face of the cytoplasmic membrane were constant with
time, those of the EF face of the peripheral vesicle doubled in number at
18 h circadian time as compared with 06 h. Particles of the 120-A size
class, in particular, were more numerous at 12 and 18 h circadian time than
at 00 and 06 h. While the finding does not provide definitive confirmation
of the membrane hypothesis for circadian rhythms, it is consistent with
this model. It is suggested that the peripheral vesicle may be the site of
bioluminescence in Gonyaulax.
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