EFFECT OF DINOFLAGELLATE BIOLUMINESCENCE ON COPEPOD INGESTION RATES1

Grazing experiments were conducted with three calanoid copepods and three species of bioluminescent dinoflagellates, using procedures which yielded samples of cultures with high and low capacities for stimulable bioluminescence. In all cases the ingestion rates were lower for the highly bioluminescent samples than for the samples having a reduced capacity for bioluminescence. These results indicate that dinoflagellate bioluminescence has survival value as a defense against copepod grazing. Of several possible mechanisms, we propose that the flash is a visual, protean display which startles or confuses the copepod sufficiently to allow the dinoflagellate to escape. The net evolutionary value is that predation would be reduced on a dinoflagellate population as a whole.