474 THE BIOLOGY OF MARINE ANIMALS 



In Lytechinus pictus, on the other hand, the testes contain about four times 

 as much carotene as the ovaries, and twice as much xanthophyll. The usual 

 carotenoids in this group are a- and /^-carotenes, and the xanthophyll 

 echinenone. The dominant carotenoid in the ophiuroid Ophidiaster is 

 astaxanthin (16, 31, 35, 36, 58, 64). 



Representatives of the major groups of molluscs have yielded caro- 

 tenoids, including many lamellibranchs, gastropods, amphineurans and 

 cephalopods. The pigments occur variously in the skin, eyes, digestive 

 glands, gonads and ripe eggs. Xanthophyll pigments known as glycymerin 

 and pectenoxanthin have been recovered from the gonads of Glycymeris 

 glycymeris and Pecten maximus, and astacene from the brightly coloured 

 Lima excavata. In Mytilus californianus the females contain about two 

 and a half times as much carotenoid (predominantly mytiloxanthin) as the 

 males, and in both sexes the pigments tend to be concentrated in the gonads. 

 Some nudibranchs, for example Hopkinsia rosacea, owe their bright colour- 

 ing to xanthophylls. The cephalopods, in general, are poor in carotenoids, 

 which have been found in the eyes, liver and ink gland but not in the skin. 

 There is some evidence that cuttlefish and octopods excrete excess caro- 

 tenoids in the ink. Starvation brings about a disappearance of carotenoids 

 from the liver and ink of Octopus bimaculatus (15, 17, 19, 31, 32, 35, 73, 

 74). 



Carotenoids are abundant and widely distributed in the Crustacea, and 

 are responsible for most of the bright colours in this class. The pigments 

 may impregnate the exoskeleton and give the animal a red coloration as 

 in Nephrops norvegicus, occur diffusely in cells, or be localized in chromato- 

 phores. They also occur in the eyes, photophores, hepatopancreas, gonads, 

 haemolymph and eggs of various species. Combined with protein, they 

 are responsible for the sombre blue, green and brown colours of many 

 decapods, for example Homarus and Palinurus. On boiling or treatment 

 with protein denaturants such as formalin or alcohol, the carotenoid 

 component is released and gives rise to the well-known red colour. The 

 presence of carotenoids in euphausiids and copepods forms an important 

 link between phytoplankton organisms, which synthesize these pigments, 

 and animals higher up in the food chain. In the North Atlantic, euphausiids 

 accumulate carotenoids more rapidly during the spring and autumn, at 

 the times of diatom outbursts, than at other seasons. The characteristic 

 carotenoid of crustaceans is astaxanthin, a dihydroxy-diketo-/?-carotene, of 

 which astacene is a derivative. Levels of astaxanthin in Euphausia superba 

 range around 6-22 jug /g. In conjunction with protein, astaxanthin forms a 

 water-soluble green pigment (ovoverdin) in the eggs of the lobster; 

 similar pigments occur in Mala squinado and the goose barnacle Lepas 

 (13, 14, 15a, 35, 53, 58). 



In the shore crab Carcinus maenas carotenoids are absorbed with the 

 food and are stored in the hepatopancreas. This store is used to supply 

 the epidermis in males and in non-gravid females, but in reproducing 

 females the carotenoids are transported in the blood to the ovaries and 



