PIGMENTS AND COLOURS 



473 



within its own tissues, including the gonads, but in another species, 

 Cribrina xanthogrammica, the carotenoids are contained in symbiotic 

 algae living inside the anemone (22, 23, 50). 



A equals 

 = CH-CH 



CH-C=CH-CH=CH-CH=C-CH = CH-CH = 



CH, 



CH, 



H 3 C CH 3 



HjjC CH 3 



— CH=CH-C=,4 = C-CH=CH 



— CH 3 ' ' 



CH 3 CH 3 



/?- CAROTENE 



Many corals and reef anemones are bright blue in colour, possibly due 

 to carotiproteins. The blue pigments in the umbrella of Scyphomedusae 

 (Cyanea, Amelia) known as cyaneins are carotiproteins, as is the blue 

 pigment velellin of the siphonophores Velella and Physalia. The brown 

 pigment responsible for the characteristic markings of Chrysaora appears 

 to be a form of cyanein and sometimes, as in Cyanea capillata, the colour 

 is brown or blue according to the variety. In addition, carotenoids are 

 accumulated in the ovaries (Amelia) (23, 31, 63, 80). 



Carotenoids in the different groups of worms have been little studied. 

 Nemertines, both littoral and bathypelagic, are frequently brightly coloured, 

 due to carotenoids located in the skin and alimentary canal. Carotenoids 

 also occur in some polyclads, serpulids and other polychaetes. The burrow- 

 ing polychaete Thoracophelia mucronata contains considerable quantities 

 of ^-carotene (0-36 mg/g tissue) (17, 20). Brightly coloured carotenoid 

 pigments are common in echinoderms, especially in the integument, 

 digestive glands, gonads and eggs of asteroids, the gonads of echinoids 

 and holothurians, and the integument of ophiuroids. Fox (16) has ob- 

 served that oxygenated carotene derivatives such as astaxanthin frequently 

 predominate over carotenes in starfishes. These animals are often coloured 

 in rich hues of blue, purple, violet, pink and brown, which are due to 

 carotenoids conjugated with proteins in the integument (Solaster, Asterias, 

 Porania). A sexual difference has been found in the carotenoid content of 

 Dendraster excentricus, in which the males contain up to three times as 

 much pigment as the females; in the males the pigment is concentrated in 

 the testes (16, 17, 31, 35, 81). 



The echinoids store large quantities of carotenoids in gonads and in- 

 testinal tissue but, in contrast to the asteroids, have little in the integument, 

 where quinone pigments often predominate instead. In Strongylocentrotus 

 pmpmatus, about 75 % of all carotenoids is located in the gonads, and the 

 carotenoid content of ovaries is three times as great as that of the testes. 



