Ecological significance of dinoflagellate bioluminescence

Graduation date: 1970The nature of the bioluminescence of Gonyaulax catenella is\ud similar to that observed for other dinoflagellates in culture, showing\ud photoperiod-entrained rhythms of luminescence and stimulability\ud with relatively constant luminescent capacity during scotophase. G.\ud catenella is very sensitive to stimulation and photoinbibition. The\ud nature of the response to stimulation by bubbling appears similar to\ud that of G. polyedra, and comparisons of the total stimulable light with\ud G. polyedra indicate that G. catenella emits approximately 6 x 10⁷\ud photons per cell, during exhaustive scotoptic stimulation.\ud Over a range of cell concentrations, the rates of cell removal\ud and filtration for Calanus pacificus when grazed on G. catenella were\ud considerably lower when the dinoflagellates were in a relatively non-luminescent\ud phase as opposed to a highly sensitive and luminescent\ud phase. These differences could not be attributed to differences in\ud particle size, culture age, distribution of dinoflagellates, ambient\ud light intensity, rhythms in copepod feeding activity, or other factors\ud reported to affect copepod grazing. Possible mechanisms of the\ud effect are discussed.\ud It is proposed that bioluminescence in dinoflagellates serves\ud as a protean display type of defense mechanism against copepod\ud grazing, has selective value, and is of adaptive and ecological significance