Circadian spontaneous bioluminescent glow and flashing ofGonyaulax polyedra

A new, fully computerized method for the measurement and analysis of dinoflagellate bioluminescence has been developed and applied to the spontaneous light emission ofGonyaulax polyedra. This light emission consists of a low-level steady glow, and occasional superimposed flashes. The instrumentation distinguishes the two components and records them separately; both exhibit circadian rhythmicity. In this paper we describe the method in detail, and show results for flashing and glow measured under light: dark cycles and under constant light of different intensities. Under constant dim light at 19°C, both rhythms exhibit two peaks during a circadian cycle; the minor ones occur approximately nine hours before the major ones. Under these conditions the major flashing peak occurs early during the subjective night, and the major glow peak at the end, about nine hours later. However, the relative phase angle between glow and flashing peaks varies with light intensity, being as little as 220 min (3.7 h) in the dark under light-dark entrained conditions, to as much as 700 min (11.7 h) in dim light under free-running conditions. The ambient light intensity also affects differentially the amount of light emitted in the two modes of spontaneous luminescence. These results suggest that the controls for the two processes must at some point diverge.