Some Reflections on the 



Control of Bioluminescence 



John Buck 

 National Institute of Arthritis and Metabolic Diseases, National Institutes 



of Health, Bethesda, Maryland 



From the information and data at hand it is evident that one cannot 

 necessarily extrapolate from one luminescent system to another or 

 from the behavior of one luminous organism to that of another. 

 Nevertheless, the work review^ed by Dr. Nicol does point to certain 

 tentative generahzations. For one thing, the simpler organisms such as 

 bacteria, protozoa, coelenterates, ctenophores, and polychaetes seem 

 either to luminesce continuously or to light up only in response to 

 external stimuli, and it is only in groups with rather well-developed 

 nervous systems that photogeny becomes subject to the precise sort 

 of regulation so well exemplified in the mating signals of fireflies. 

 Secondly, it is clear that the abihty to emit sharply delimited flashes 

 of Hght does not depend on a highly developed nervous system but 

 on intracellular Hght production. Tlius, for example, in Chaetopterus 

 and Cypridina, animals with well-developed nervous systems, light 

 production is extracellular and the luminosity decays slowly, whereas 

 the primitively organized Noctiluca, ReniUa, and Mnemiopsis produce 

 flashes not inferior in temporal control to those of many fireflies. 

 Extracellular luminescences are characterized, in addition, by rapid 

 "fatigue" due to exhaustion of the luminous excretion, whereas intra- 

 cellular photogeny may sometimes persist through many hundred 

 successive flashes. 



The main emphasis of Dr. Nicol's paper is on the properties of the 

 nervous systems of various luminous organisms (and in this he pre- 

 sents a strong case for photogeny being as accurate and critical an 



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