76 GENERAL CONCEPTS 



Figure 4.3. Anomalops katoptron, a luminescent fish from the waters of the Malay 

 Archipelago. The crescent-shaped luminescent organs below the eyes are equipped with 

 reflectors. (After Steche.) (Villee; Biology.) 



teria as well, have an enzymatic mechanism for the production of light. 

 Luminescent animals are found among the protozoa, sponges, coelen- 

 terates, ctenophores, nemerteans, annelids, crustaceans, centipedes, milli- 

 pedes, beetles, flies, echinoderms, molluscs, hemichordates, tunicates and 

 fishes. From this wide and irregular distribution of the light-emitting 

 ability, it is clear that the enzymes for luminescence have appeared in- 

 dependently in a number of different evolutionary lines. It is some- 

 times difficult to establish that a given organism is itself luminescent; 

 in a number of instances animals once believed to be luminescent have 

 been shown instead to contain luminescent bacteria. When the bacteria 

 are removed the animal is no longer able to emit light. Several different 

 exotic East Indian fish have light organs under their eyes in which live 

 luminous bacteria (Fig. 4.3). The light organs contain long, cylindrical 

 cells which are well provided with blood vessels to supply an adequate 

 amount of oxygen to the bacteria. The bacteria emit light continuously 

 and the fish have a black membrane, somewhat similar to an eyelid, that 

 can be drawn up over the light organ to turn off the light. How the 

 bacteria come to collect in the fish's light organ, as they must in each 

 newly hatched fish, is a complete mystery. 



Some animals have accessory lenses, reflectors and color filters with 

 the light-producing organ and the whole complex assembly is like a 

 lantern. Certain shrimp have such complicated light-emitting organs. 



The production of light is an enzyme-controlled reaction, the de- 

 tails of which differ in different organisms. Bacteria and fungi produce 

 light continuously il oxygen is available. Most luminescent animals, in 

 contrast, give out flashes of light only when their luminescent organs 

 are stimulated. The name luciferin has been given to the material which 

 is oxidized to produce light and luciferase to the enzyme which catalyzes 

 the reaction. The luciferin and luciferase from one species may be quite 

 different chemically from those in another. The oxidation of luciferin 

 by luciferase can occur only in the presence of oxygen. It is possible to 

 extract luciferin and luciferase from a firefly, mix the two in a test tube 

 with added magnesium and adenosine triphosphate, and demonstrate 

 the emission of light in the test tube. The energy for the reaction is 

 supplied by the ATP. 



