CAROTENOIDS 



of a known analogous situation (in algae) of preferential oxidation of 

 carotenoids, and (b) the absence of zeaxanthin from fresh gathered 

 Bacillariophyceae. It should be noted, however, that strong support 

 for Kylin's thesis comes from the fact that Karrer and Strong ^ ^ « have 

 isolated crystalline zeaxanthin from the brown alga Halysersis polypo- 

 dioides, and that in fading green leaves, zeaxanthin is relatively the most 

 stable carotenoid {see p. 23). 



Differential carotenoid distribution has been noted in F. serratuSj 

 F. vesiculosus and Ascophyllum nodosum ^^^'^^''. The bright orange 

 yellow of the male gametes is due almost entirely to [3 -carotene and 

 the olive green of the ova to a mixture of fucoxanthin and chlorophyll. 

 This will be discussed later {see p. 147). 



Seybold and Egle's^*^ quantitative study of Fucus and Laminaria 

 species emphasises the fact that fucoxanthin is the predominating 

 pigment ; it occurs in concentrations 5-8 times greater than does 

 p-carotene, which itself is more abundant than the ** xanthophylls- 

 not-fucoxanthin." The mean values obtained on Fucus and Laminaria 

 were, for carotenes, xanthophylls not fucoxanthin, and fucoxanthin, 

 respectively, 3-8, 2-5, and 13-8, and 1-5, 0-7 and 8-6 mg. per 100 g. wet 

 weight (see also Table 22). 



Rhodophyceae 



The earlier work of Kylin 1 2 4, 1 5 s j^^s been extended and to a great 

 extent confirmed by Carter, Heilbron and Lythgoe. ^ ^ 8 ^-carotene 

 is always present ; considerable amounts of oL-carotene are present in 

 some species {e.g. Ceramium rubrum) whilst in others {e.g. Polysiphonia 

 nigrescens, it does not exist. ^ ^ » The most striking finding after examin- 

 ing numerous members of the seven orders of this class was the complete 

 absence of any characteristic carotenoid ; lutein (xanthophyll) is the 

 principal xanthophyllic pigment and taraxanthin is generally present. ^ " ^ 

 Only one member of this group was found which contzm^d fucoxanthin, 

 this is Polysiphonia nigrescens. No explanation of this is apparent at the 

 moment for there is no morphological abnormality about this alga. 



The quantitative distribution of carotenoids in the Rhodophyceae 

 is very similar to that in the Chlorophyceae ^ * ^ (Table 22). 



DiNOPHYCEAE (PeRIDINIEAE) 



p-carotene is the main hydrocarbon carotenoid present in this 

 group. An apparently characteristic pigment, peridinin, was detected 

 in Peridinium spp. by KyHn. ^24 a further examination ^ '^ » of this 

 pigment has led to the suggestion that it is identical with the xantho- 

 phyll, mlcatoxanthin, first isolated in 1935 from Anemonia sulcata ^^'^ 



134 



