Mechanical stimulation of bioluminescence in the dinoflagellate Gonyaulax polyedra Stein

Cultures of the marine dinoflagellate Gonyaulax polyedra Stein were exposed to a variety of flow regimes in small tubes, pressure chambers, and vessels in which objects could be rotated. Bioluminescence was mechanically stimulated by changes in shear, acceleration, and pressure, not by constant values of these parameters. In a biological context, such stimuli would be associated with waves and other surface turbulence, with moving objects such as ships or some large marine organisms, or with close or direct contact as would occur if the dinoflagellate is a prey item. The effects of pressure are complicated by the observation that the luminescence response did not occur in the bulk of the fluid in a pressure chamber, but was confined to the liquid boundaries. The importance of luminescence at surfaces was also seen when objects were rotated in suspensions of G. polyedra; light emissions were restricted to regions with sharp shear gradients. These data were obtained using an image intensifier which made it possible to visualize the spatial pattern of luminescence in the various flow regimes studied. Past results obtained with photo-multipliers are shown to be misleading.