FLASH KINETICS AND SPATIAL PATTERNS OF BIOLUMINESCENCE IN THE COPEPOD GAUSSIA-PRINCEPS

Kinetics and local spatial patterns of bioluminescence in the mesopelagic copepod Gaussia princeps (T. Scott), collected by net off the coast of southern California, USA, were investigated from 1986 to 1989. Luminescence elicited by single electrical stimuli began as a localized secretion from any of 16 widely distributed sites on the body. Appendage or body movements swept the particulate luminescent exudate away from the cuticle. Three types of single flashes were identified in response to single electrical stimuli, including a fast flash of ca. 2 s duration, a long flash of 7 s duration, and a 17 s slow flash. In addition, in 20% of the tests a fourth, two-component flash consisting of a fast or long component followed by a slow component was elicited. Frequency of the four flash types was dependent on the recovery time after collection. Shorter, less intense fast and long flashes occurred early in the recovery period, and longer, brighter slow and compound flashes became more common as recovery progressed. The laboratory handling protocol strongly affected total stimulable light (TSL). Strong handling resulted in a reduced TSL, which recovered to the original level upon termination of the stimulation. TSL and flash kinetics in the laboratory were highly dependent on the chronic laboratory stimulation protocol and represent an equilibrium between recovery of luminous reserves and re-stimulation. Flash kinetics and TSL were also affected by the frequency of stimulation. Higher stimulation rates resulted in greater temporal summation of the flashes, a decreased response duration, and a lower TSL. Stimulus frequency and duration therefore determine the nature of the bioluminescent response. Flash kinetics and TSL made with either in situ bathyphotometric measurements of laboratory measurements strongly depend on the extent of prestimulation, depletion of bioluminescent reserves, and the level of stimulation inherent with the particular device.