CAROTENOIDS 



Fox and Scheer ' • in their detailed study of echinoderm pigments 

 found that in the asteroids, Astropecten californicuSy Patina miniatay 

 Pisaster ochraceous^ and P. giganteus, that the predominant pigment 

 was astaxanthin, that no esterified xanthophylls were present except 

 perhaps in traces in P. giganteuSy and that the free xanthophyll fraction 

 was more abundant than the carotene fraction, which was mainly 

 (3-carotene. A pigment very similar to zeaxanthin was present in con- 

 siderable amounts except in A. calif ornicus in which pectenoxanthin 

 (see p. 1 76) was detected. P. ochraceous apparently contained mytiloxan- 

 thin and P. giganteus, metridin. Mytiloxanthin is the characteristic 

 pigment of the Califomian mussel and in P. ochraceous may be derived 

 from this mollusc on which it feeds extensively. A carotenoid-protein 

 complex existed only in P. giganteus, the carotenoid involved being 

 metridin. (See also Table 24.) 



There is an interesting preferential accumulation of carotenoids in 

 certain organs of these asteroids. For example, the carotenoids in the 

 skin of P. ochraceous amounted to 49 per cent, of the total, and in the 

 pyloric caeca to 4-7 per cent. The situation is reversed in P. giganteus^ 

 the corresponding figures being 7-2 per cent, and 22 per cent. ; why 

 this should be so is not easily apparent. The concentration of caroten- 

 oids in the pyloric caeca is higher than that in the skin in both species, 

 being fifty times higher in P. ochraceous and twice in P. giganteus. 



Lonnberg^' has also noted carotenoids in the pyloric caeca of 

 Astropecten irregularis and Henricia sanguinolenta. 



Ophiuroidea 



Qualitative detection of carotenoids has been made by Lonnberg * ' 

 in a number of ophiuroids.* In the three species studied by Fox and 

 Scheer, ^ ® Ophiopteris papulosa, O. spiculata, and Ophiothrix rudis, the 

 outstanding feature was the absence of carotenes. The xanthophyllic 

 fraction contained a pigment similar to taraxanthin and a new very 

 unstable pigment which was not characterized. O. papulosa also con- 

 tained pectenoxanthin, and in all species the presence of xanthophyll 

 esters was consistently indicated. 



HOLOTHUROIDEA 



Lonnberg 3' claims that the red-yellow gonads of Mesothuria 

 intestinalis and the blue gonads of Cucumaria lactea contain a mixture 

 of carotenoids. Fox and Scheer ^ * found small amounts of carotenoids 

 in C. lactea (0-029 mg. per lOOg.), of which 48 per cent, is carotene. As 

 echinenone (see p. 163) is present, this figure for carotene is probably 



♦ See Table 27. 

 162 



