The ctenophore Mnemiopsis leidyi is an opportunistic species that can be extremely abundant and invasive in many parts of the world. It is well known for its bright bioluminescence, but its light emission response to flow stimulation has not been rigorously quantified. The objective of this study was to determine the luminescent response of cydippid larvae of M. leidyi to two types of mechanical stimuli, including an impeller pump within the UBAT bathyphotometer and stirring as the stimulus within an integrating sphere. Tests were conducted with less than one week old cydippid larvae, analyzing flash parameters of rise time, peak intensity, decay slope, decay time, total integrated emission (TMSL), integrated flash emission, and flash duration. Cydippid larval size had a positive correlation with peak intensity. There were four patterns of bioluminescent responses from the UBAT but they did not have statistically different flash kinetics. For the integrating sphere, the average peak intensity and TMSL were much greater than for the UBAT, possibly due to the two forms of stimulation. However, a constant phosphorescent emitter was 2.6 times brighter when measured with the integrating sphere compared to the UBAT, suggesting inaccurate photon calibration of the UBAT perhaps due to light measurement geometry. This study provides a well-defined baseline of cydippid larvae flash responses that can be used for interpreting field measurements made with bathyphotometers and to determine their contribution to the bioluminescence potential of waters where they are present.
|