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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.

In order to discover the intracellular location of luciferase in dinoflagellates, sections from a number of species were treated with a polyclonal anti-luciferase and the bound antibody was visualized at the electron-microscope level by indirect immunogold labelling. In two species of Pyrocystis and in Noctiluca, as in Gonyaulax, antibody became bound to dense vesicles, which correspond in size and position to light-emitting bodies detected in previous work. These vesicles resemble microsomes, are bounded by a single membrane and sometimes project into the vacuole. Unexpectedly, the trichocysts of Gonyaulax and Noctiluca and the related mucocysts of Pyrocystis also bound the antibody. This cross-reaction seems quite independent of bioluminescence, since the trichocysts of the non-luminous Cachonina also reacted positively. The possibility is discussed that a protein, different from luciferase but having some antigenic similarity, is present in trichocysts and related organelles.

The luminescence of the marine dinoflagellate Gonyaulax polyedra shows an endogenous diurnal rhythm. The effect of light during the phase of low luminescence capacity may be observed as an enhancement of luminescence during the subsequent bright phase. During the bright phase, however, illumination diminishes the capacity for luminescence. The action spectra for these two effects of light have been determined, and the major pigments of Gonyaulax have been examined. A consideration of the action spectrum and the pigment complement of Gonyaulax suggests that photosynthesis during the day is responsible, directly or indirectly, for the enhancement of luminescence during the following night. Photoinhibition of luminescence is in part attributable to light absorbed by the photosynthetic pigments. However, activity observed in the far red region of the spectrum beyond the absorption maximum of chlorophyll a suggests that an additional pigment, present in small amounts, may also act as sensitizer for photoinhibition.

The luminescent marine dinoflagellate, Gonyaulax polyedra, exhibits a diurnal rhythm in the rate of photosynthesis and photosynthetic capacity measured by incorporation of C(14)O(2), at different times of day. With cultures grown on alternating light and dark periods of 12 hours each, the maximum rate is at the 8th hour of the light period. Cultures transferred from day-night conditions to continuous dim light continue to show the rhythm of photosynthetic capacity (activity measured in bright light) but not of photosynthesis (activity measured in existing dim light). Cultures transferred to continuous bright light, however, do not show any rhythm. Several other properties of the photosynthetic rhythm are similar to those of previously reported rhythms of luminescence and cell division. This similarity suggests that a single mechanism regulates the various rhythms.

The action spectrum for changing the phase of the rhythm of luminescence in the marine dinoflagellate Gonyaulax polyedra has been determined. Maxima in effectiveness were found at 475 and 650 mmicro. The significance of these findings is discussed.