Luminescence in Marine Organisms^ 



^j J. A. C. NicoL 



The Marine Biological Laboratory 

 Plymouth, England 



[With 4 plates] 



The study of bioluminescence, or light production by plants and 

 animals, has made rapid strides as new and highly sensitive liglit de- 

 tectors have become available. The subject is of interest for a num- 

 ber of reasons, among which appeal to the imagination may Avell be 

 included. Bioluminescence is a specialized function exhibited by a 

 small minority of species, yet among them there is a great diversity of 

 forms. It must therefore have developed independently in the couree 

 of evolution in species that have little else in common. An excep- 

 tion is that in the deep sea, where sunlight does not penetrate, most 

 of the organisms that have been observed are luminescent. Here, as 

 elsewhere, it appears that luminescence, at least in its more highly de- 

 veloped forms, is of biological value to many of the species that possess 

 it. Finally, the subject is one that gains from being viewed as a 

 whole. The chemistry of bioluminescence, coupled with the fact that 

 luminescence is shown by many bacteria for which it has no biological 

 significance, provides a clue to its origin. This therefore is a good 

 point from which to begin a survey of the subject. 



CHEMISTRY OF LUMINESCENCE 



The light of bacteria, as of other luminescent organisms, is emitted 

 during the course of a chemical reaction when a luminous substrate, 

 luciferin, is oxidized by an enzyme, luciferase, in the presence of 

 molecular oxygen. The biochemical mechanism of this reaction has 

 been determined, largely through the efforts of E. L. Stehler and his 

 colleagues in Chicago. It turns out that the luciferin of bacteria is a 

 flavin closely allied to a yellow pigment, riboflavin, also known as 

 vitamin B2 or vitamin G, which is itself luminescent. Bacterial 

 luciferin is, in fact, an aldehyde complex of dihydroflavin mono- 

 nucleotide. It is oxidized through the agency of luciferase to flavin 



» Reprinted by permission from The Times Science Review, summer 1960 (London). 



447 



