LUMINESCENCE 



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shine with a yellowish glow. The deep-sea squid Lycoteuthis diadema is 

 noteworthy in that it produces light of three different colours. Chun, on 

 the Valdivia expedition, was able to observe live specimens brought up 

 from 3,000 metres in the Indian Ocean. He found that most of the light- 

 organs in that animal shone with a white radiance, but the two anal lights 

 were ruby red, the middle visceral light ultramarine and the two middle 

 ocular lights clear sky blue. Beebe and his colleagues have recorded much 



400 



500 



600 



700 



700 



Wavelength - m/i 



Fig. 13.1. Spectral Composition of the Light of Several Marine 

 Animals. A, Atolla wyvillei. B, I, Chaetopterus variopedatus, II, Polynoids. C, 

 Cypridina hilgendorfii (from Coblentz and Hughes (15). D, Pholas dactylus. 



interesting information about the light of bathypelagic fish (14a, 28, 36a, 

 49a, 49a 1 ). 



The colour characteristics of the light produced are usually due to 

 chemical peculiarities of the reacting substances. In some animals, how- 

 ever, the light passes through coloured layers overlying the photogenic 

 cells, and it has been suggested that such layers may act as niters or absorp- 

 tion screens and determine the colour of the light emitted. In the deep-sea 

 shrimps Systellaspis and Sergestes, for example, the lens, or the photogenic 

 cells themselves, are tinted blue by carotiprotein, and in the bathypelagic 

 squid Lycoteuthis diadema the external layer of the anal light-organ is 

 ruby red. However, the exact role which such screens play in determining 

 the colour of the light emitted cannot be evaluated without knowledge 



