A decrease in temperature triggers a luminescent response in Noctiluca scintillans

Noctiluca scintillans (Macartney) Kofoid, a typical bioluminescentorganism, is known to respond to a mechanical stimulus by emittinglight. We found that a luminescent response could also be triggeredby lowering the temperature of the environment, but not by raisingit. This response was analyzed with respect to the rate of decreasein temperature. The results showed that the probability of theresponse was positively related to the rate of the decreasein temperature. The sites of initiation of the luminescent responsewere distributed randomly all over the surface of the cell body.The flash response that was triggered by a decrease in temperaturewasquite similar to that triggered by a mechanical stimulusat the lower temperature in terms of duration, as wellas interms of the velocity of expansion of the excited region. Afatal response, namely a slowly propagating flash (SPF), wasalso recognized.