Characterization of the in vivo bioluminescence and photoluminescence rhythms of the dinoflagellate, Alexandrium tamarense
Date Issued
2012
Date
2012
Author(s)
Shyang Tai, Sheau
Abstract
Bioluminescence of dinoflagellates is one of the interesting topics which have attracted the attention of researchers, but its characters and mechanisms are yet to be determined. Bioluminescence of A. tamarense was observed only in the dark period upon physical stimulation by shaking, but not in the light period when the cultures were maintained and acclimated to a daily 24 hours cycle of alternative light and dark period. These observations were being operated by using our newly designed instrument. Photoluminescence of the in vivo luciferin was detected under a fluorescent and a laser scanning confocal microscope that showed the luciferin-containing scintillons being located on the peripheral of cell cytoplasm and appeared only in dark period. It was also evidenced by the absence of such photoluminescence in both light and dark period of non-bioluminescent Alexandrium minutum. At the meantime, the chlorophyll a containing chloroplasts were found to be located at the cell peripheral during light period and in the center during dark period, which only being reported in Pyrocystis species so far. Although bioluminescence in other dinoflagellates was being described as circadian-regulated, our observation on A. tamarense bioluminescence showed more light-regulated. Shorten of the dark period also shorten the period of bioluminescence. However, unlike the light-regulated bioluminescence expression in A. tamarense, the aggregation of luciferin observed by its photoluminescence were found unaffected by light and followed the circadian rhythm for the first two cycles and diminished under continuous dim light. This expression was also different from other dinoflagellates which their circadian rhythms can sustain for up to twenty cycles or more. Besides, the circadian rhythmic photoluminescence of luciferin aggregation could be broken down by continuous four hours of strong illumination, while removal of light could induce another cycle of bioluminescence as in our observation in A. tamarense. Furthermore, this intracellular rhythm can be acclimated, but within a limited capacity, to different photoperiod (LD 8:16, LD 12:12 and LD 16:8) and remained a 12 ± 2 hours of bioluminescence duration. Although our study in A. tamarense bioluminescence characteristics was just the initiatory to this field, further investigations of those findings can not only lead to a deeper understanding of the circadian control in bioluminescence of this species, but also the circadian oscillation principles common to all organisms.
Subjects
Alexandrium tamarense
Bioluminescence
Photoluminescence
Circadian rhythm
Light regulation
Photoperiod acclimation
Type
thesis
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