486 THE BIOLOGY OF MARINE ANIMALS 



pigmentation; moreover each animal reverted to the colour variety to 

 which it originally belonged, namely red, brown or green. This result 

 means that the animals either regulate the kinds of carotenoids which they 

 absorb, or absorb all indifferently and metabolize them in different ways. 

 In contrast to Actinia is the plumose anemone, Metridium senile, whose 

 pigments are very stable, and which does not change in colour over long 

 periods under diverse conditions of feeding and starvation (22). 



In general, xanthophylls are assimilated and stored by most animals in 

 preference to carotenes, but interesting exceptions are seen among the 

 sponges where carotenes tend to predominate over xanthophylls. Also, the 

 polychaete Thoracophelia mucronata contains appreciable quantities of 

 /^-carotene derived from its food, but excludes the attendant xanthophylls. 

 Astaxanthin and related pigments, which, as we have seen, occur widely 

 among invertebrates, are derived from the oxidation of ^-carotene and 

 certain xanthophylls in the diet (16, 17, 20, 22). 



Other pigments of exogenous origin, previously described, are the 

 chlorophyll derivatives and bile pigments occurring in phytophagous and 

 parasitic species. No studies have been devoted to possible correlations 

 between concentrations of green chlorophyll-like pigments in marine 

 animals and the intake of algal food, but the relationship of breakdown 

 products such as biliverdin to ingested haemoglobin is very close. 



In dealing with the biological significance of pigments and colours we 

 shall consider the following topics, namely metabolic functions, environ- 

 mental influence on colour, colour patterns, inheritance of colours, sexual 

 coloration and adaptive and cryptic coloration. 



Metabolic Functions 



From a review of the distribution of carotenoid pigments one striking 

 fact that emerges is the accumulation of these pigments in reproductive 

 organs. Carotenoids are actively mobilized into the gonads during sexual 

 reproduction and, in some animals, they are also rendered water-soluble 

 by conjugation with proteins. In females of the shore crab Carcinus maenas 

 a yellow carotenoid increases in the blood as the ovary matures, and is 

 laid down in that organ. Prior to spawning, carotenoids are also in active 

 movement in fish: in the killifish Funduhis parvipinnis for example, the 

 males increase the xanthophyll content of their skin, while the females 

 transfer their stores to the ripening eggs. A careful study of Mytilus 

 califomianus has shown that shed ova contain qualitatively the same caro- 

 tenoids as the ovaries, but the difference in amount between ripe and spent 

 females cannot be accounted for by the carotenoid content of the eggs. 

 Similarly, although the spermatozoa are colourless, spent males contain 

 less carotenoid pigment than unspawned males. These facts suggest that 

 carotenoids play some role in spawning and are used up during the process 

 (16,31,35,73). 



Eggs of many animals are well supplied with carotenoids, but the role 

 they play in normal embryonic development is obscure. Some suggestions 



