10 SURVEY OF LUMINOUS ORGANISMS 



dark. The effect of strong light is on the luminescent system. Weak 

 light will inhibit the excitation mechanism (Moore, 1924). No day- 

 night rhythm of luminescence has been established in the ctenophore, 

 Mnemiopsis, but among dinoflagellates, a day-night rhythm has been 

 described. The complicated details of light inhibition have been de- 

 scribed in Bioluminescence (Harvey, 1952), and the action on various 

 groups is summarized in Table I, column 7. 



This survey of luminous organisms has indicated certain well-defined 

 biochemical groups, but there are many others about which too little 

 is known to attempt a logical separation. Luminous animals are scat- 

 tered over the evolutionary tree from Protozoa to fish without any 

 indication of direct evolutionary descent. One species of a genus may 

 be luminous and another not. One variety of a fungus may be lumi- 

 nous and another not. The existence of nonluminous mutants of lumi- 

 nous bacteria has been known since the work of Beijerinck (1912). 

 The author ( 1932, 1953 ) has taken the viewpoint that luminescence 

 has arisen independently in various phyla of the animal kingdom, 

 probably from some slight change in chemical systems common to 

 cells in general, most likely the cell-respiratory systems. 



There is every evidence that the luciferins of fireflies, bacteria, and 

 Cypridinae are chemically quite different and must be prefixed by the 

 word firefly luciferin, bacterial luciferin, etc., in order to designate 

 them. The bioluminescence emission spectra of various organisms 

 range in the wavelength regions of red to violet, just as do the 

 chemiluminescence spectra of quite unrelated organic compounds — 

 metal prophyrins, red; pyrogallol, yellow; dimethyldiacridinium nitrate, 

 green; 3-aminophthalic hydrazide, blue luminescence. Substituted 

 groups on these compounds will change the chemiluminescent inten- 

 sity markedly and the maximum wavelength of emission slightly, but 

 thus far spectral energy curves have given little clue to chemical 

 structure. 



It must be emphasized that small shifts in maximum emission of 

 bioluminescences have little meaning, since the presence of absorbing 

 pigments in cells and the phenomenon of differential absorption may 

 change the emission spectrum of any luminous animal. The latter effect 

 is particularly well seen in Spruit- van der Burg's ( 1950 ) study of the 

 relation of density of suspension to bacterial luminescence emission. 



