Most dinoflagellates emit about 6e8 photons in a flash lasting only about 0.1 second. Much larger organisms such as jellyfish emit about 2e11 photons per second for sometimes tens of seconds. The intensity of luminescence by photosynthetic dinoflagellates is strongly influenced by the intensity of sunlight the previous day. The brighter the sunlight the brighter the flash. Kinetics Some organisms emit light continuously, but most emit flashes of durations ranging from about 0.1 s to 10 s.
Some dinoflagellates can respond repetitively to excitation over a short period.
In most multicellular species luminescence is neurally controlled. Thus in some fish the sympathetic nervous system controls luminescence by way of the neurotransmitter nor-adrenaline. In fireflies the transmitter is glutamate. In most marine invertebrates the transmitters are unknown. Mechanical deformation causes an action potential sweeping over the vacuole membrane and this is thought to induce light emission by admitting protons from the acidic vacuole into contact with the cellular elements that contain the light emission chemistry.