PHOTOINHIBITION OF STIMULABLE BIOLUMINESCENCE IN MARINE DINOFLAGELLATES

Abstract— Different genera of bioluminescent photosynthetic dinoflagellates exhibit different mechanisms for the inhibition of stimulable bioluminescence during daylight. These are (a) reduction in bioluminescence capacity, (b) increased refractoriness to mechanical stimulation, and (c) inhibition of transmission of signals from mechanical receptor sites to bioluminescence emission sites. The increase in stimulable bioluminescence that in nature mirrors the decrease in sunlight intensity prior to sunset is dependent upon the logarithm of the ambient irradiation intensity. Photoinhibition of bioluminescence in all species examined except Gonyaulax polyedra is the result of absorption of light in the blue region of the spectrum.     

THE COLORS OF FIREFLY BIOLUMINESCENCE—II EXPERIMENTAL EVIDENCE FOR THE OPTIMIZATION MODEL*

Abstract— The shapes, the peak wavelengths and the close matching of bioluminescence colors to visual spectral sensitivities in North American firefly species are consistent with the predictions of a spectral optimization model for selection in evolution (Seliger et al., 1982). A screening pigment found by microspectrophotometry in the rhabomeres of Photinus pyralis has the absorbancc characteristics predicted by the model. The biologically effective adaptation, a dimensionless ratio proportional to the relative advantage of a species to detect bioluminescence during twilight. has been calculated from experimentally determined distributions of ambient spectral radiances, visual spectral sensitivities and bioluminescence emissions and is shown to correlate both with color of bioluminescence and with the timing of initiation of flashing activity. The colors of firefly bioluminescence are therefore species-specific adaptations to optimize the detection of bioluminescence in the different photic environments in which the species have evolved.     

ACTION SPECTRUM FOR THE PHOTOINHIBITION OF BIOLUMINESCENCE IN THE MARINE DINOFLAGELLATE DISSODINIUM LUNULA

Abstract— The fractional photoinhibition of the mechanically stimulable bioluminescence in the vacuolar dinoflagellate Dissodinium lunula is proportional to the logarithm of the exposure. The action spectrum for this photoinhibition has been determined by measuring threshold exposures in absolute units of photons cm⁻². The threshold exposure at the wavelength of maximum sensitivity, 450 nm, was 2 ± 10⁻² photons cm⁻². The action spectrum is consistent with absorption by a blue light receptor pigment shielded by a nonphotoactive pigment which absorbs in the region of the bioluminescence emission spectrum. It is suggested that there may be some selective advantage for this absorbing pigment in the vacuolar dinoflagellates in order to prevent the organisms from being photoinhibited by their own bioluminescence.     

THE COLORS OF FIREFLY BIOLUMINESCENCE—I. OPTIMIZATION MODEL*

Abstract— A model is developed for the optimization of signal-to-noise ratio for the detection of bioluminescence by fireflies during twilight. The relative degree of optimization is derived in terms of a dimensionless ratio, a biologically effective adaptation. The numerical values of this adaptation can be used to predict the sequence of adaptations of both visual spectral sensitivities and bioluminescence spectral emissions that result in the range of colors of bioluminescence of fireflics from green through yellow. It is shown that a narrowing of visual spectral sensitivity via a screening pigment pathway in order to discriminate against green ambient light is more efficient than a shift in visual spectral sensitivity via change in the opsin photoprotein. The model predicts that the range of wavelengths for the peak intensities of bioluminescence for North American fireflies should be between 550 and 580 nm and provides the physical basis for the observations that in general dark-active firefly species cmit green bioluminescence and twilight-active firefly species emit yellow bioluminescence.     

EMISSION SPECTRUM OF THE MICROSOMAL CHEMILUMINESCENCE OF A PROXIMATE CARCINOGEN, 7,8-DIOL-BENZO[a]PYRENE, DETERMINED WITH A WEDGE INTERFERENCE FILTER SPECTROMETER*

Abstract— The emission spectrum of the microsome-mediated chemiluminescence of a proximate carcinogenic metabolite of benzo[a]pyrene, 7,8-diol-benzo[a]pyrene. has been measured with a wedge interference filter spectrometer calibrated with known chemiluminescent and bioluminescent reactions. This instrument has a noise equivalent signal at 490 nm (bandpass 24 nm) of 10⁴ photon s-¹ at 20°C. Spectral and kinetic data indicate that the microsomal chemilurninescence of this metabolite is an exiplex chemiluminescence that proceeds through a dioxetane intermediate.     

Absolute values of photon emission from the marine dinoflagellates Pyrodinium bahamense, Gonyaulax polyedra and Pyrocystis lunula

Abstract— The total photons emitted per organism upon complete stimulation during the dark phase of their photoperiod for P. bahamense, G. polyedra and P. lunula are 2·8 × 10⁸± 15%; 1·2 × 10⁸± 12% and 40 × 10⁸± 11% respectively, P. bahamense in natural populations in Jamaica. W. 1. emitted the same total stimulable light per organism as in laboratory cultures. The bioluminescent emission spectra are the same for all three species (v_max.= 20.860 cm^-1).     

REVERSION PROFILES OF COOL WHITE FLUORESCENT LIGHT COMPARED WITH FAR ULTRAVIOLET LIGHT: HOMOLOGIES AND DIFFERENCES

Abstract— General Electric and Sylvania 15 W coolwhite fluorescent lamps emit roughly 6% of their total irradiance as light in the UV spectrum. Illumination of sensitive Salmonella tester strains results in both lethal and mutagenic activities. In contrast, comparable Philips lamps emit lower levels of U V light, especially UVB, and exhibit no detectable lethal or mutagenic effects. The spectra of mutations induced by General Electric coolwhite lamps in histidine-requiring base substitution mutants hisG46 and hisG428 ("reversion profiles") resemble mutagenesis by far UV light (UVC) and differ quite markedly from the spectra of mutations that occur spontaneously. Coolwhite and UVC reversion profiles are not identical, however. The percentage of C to A transversion mutations induced in hisG46 are elevated over those found after UVC treatment, and a strong bias for one particular class of tandem base substitutions (TAA → T GT ) prevails after treatment of hisG428 with coolwhite light, a bias not observed with UVC. Increased attention needs to be given to minimization of exposure to UV light from fluorescent lamps commonly used in homes and workplaces.