CAROTENOIDS 



A small proportion of the ovarian, but none of the testicular caroten- 

 oids, was attached to protein. The brownish-green colour of the 

 ovaries was, however, not to any significant extent due to carotenoids, 

 but to a complex formed between a protein and an as yet unidentified 

 greyish-green pigment. This pigment appears somewhat similar to 

 the water-soluble pigment found in the flesh of some fish. 



The pink to red colour (according to season) of the testes is due to 

 the carotenoids present, the green pigment being always absent. 



After spawning the female gonads are much paler and contain less 

 carotenoids, whereas the male gonads assume a brick red colour and 

 contain, as far as can be ascertained, nearly the same amount of caro- 

 tenoids as before spawning ; ^ * from a microscopic examination it 

 appears that the spermatozoa contain only traces, if any, of carotenoids. 

 There is a close analogy here with the mussel, M. californicus. 



It has recently been stated that young Aplysia (delipans and punctata) 

 contain unidentified carotenoid and chlorophyll derivatives. In dark- 

 adapted neurons, irradiation with light of wavelengths absorbed by 

 the carotenoids increases the reaction time of the neuron ; the reverse 

 occurs when light of wavelength corresponding to that absorbed by 

 chlorophyll is used. It is further claimed that irradiation of the caro- 

 tenoid in vivo increases the number of absorption bands in its spectrum. 

 Irradiation of a solution of the pigment in vitro reduces the number of 

 bands. ' ' 



To conclude this chapter, all the available qualitative and quanti- 

 tative data on carotenoid distribution are recorded in Tables 28 and 29. 



180 



