VARIABILITY IN FLASH CHARACTERISTICS OF A BIOLUMINESCENT COPEPOD

Bioluminescence of the copepod, Pleuromamma xiphias, was investigated with an optical multichannel analyzer(OMA) to measure emission spectra, an integrating sphere-photon counting detector system to determine flash kinetics and quantum emission, and an ISIT video system to image spatial patterns of emission. Light emission was in the blue spectral region, with maximum emission at approximately 492 nm. Spectral waveforms were unimodal, or bimodal with the secondary peak at 472 nm. Flashes in response to a single stimulus consisted of two components: a fast component attaining maximum intensity in under 100 ms, and a slow element which peaked after 600 ms. The fast component originated from thoracic and abdominal light organs while the slow component represented a large expulsion of luminescent material from the abdominal organ only. Both components exhibited first order exponential decay although the decay rate of the fast component was approximately one order of magnitude greater. The typical flash response to a single stimulus exhibited a response latency of 30 ms, initial rise time of 87 ms, duration of 2.4 s, and quantum emission of 1.4 x 10¹⁰ photons flash^-1. Quantum emission increased with increasing stimulus strength. Both response waveform and total quantum emission were affected by the frequency of electrical stimuli. Stimulation at 1 Hz generated the greatest luminescence, averaging 1.1 x 10¹¹ photons response^-1 for 11 s emissions. Higher rates of stimulation decreased total quantum emission and response episode duration, and resulted in greater temporal summation of the emission waveform. Variability in flash characteristics due to electrical stimulation suggests a versatility of luminescent displays in situ.