Chapter V 



Carotinoids in Invertebrates 



The causes of the colorations and pigmentations encountered among 

 the lower forms of animal life have not been without interest to 

 the biologists. It is to be expected that the developments in the 

 field of chromatology which took place during the 19th century should 

 be accompanied by studies of invertebrate pigments by the zoologists 

 and others interested in these forms of life. These studies have an 

 especially important bearing on the subject of the distribution of 

 carotinoid pigments among animals because, as has already been 

 pointed out, evidence of a more definite nature has been presented for 

 the existence of these plant pigments in animals of the invertebrate 

 group, than for a number of the vertebrates. It should be under- 

 stood, however, that carotinoids do not predominate among the pig- 

 ments of the lower animals. On the contrary, one would hardly be 

 justified in asserting that the carotinoids predominate among the pig- 

 ments of yellow to red color encountered among the invertebrates. 

 As in the case of plants, it appears that as one descends the scale of 

 living forms, non-carotinoid pigments of yellow to red hues seem to 

 be met more and more frequently. For example, it will be shown 

 presently that carotinoids are undoubtedly abundantly present in the 

 larva and pupa? of butterflies and moths, but the brilliant reds, golds 

 and yellows seen in the butterflies themselves are apparently caused 

 by pigments of entirely different characteristics. Again, among the 

 Crustacea and worms, other red and yellow pigments are often the 

 cause of colorations. These facts, however, do not detract from the 

 interest which is naturally aroused by the presence of the carotinoids 

 in at least some species of almost all the main groups of invertebrate 

 animals. One might think, perhaps, that the simpler digestive appa- 

 ratus of the lower animals would insure a more abundant distribution 

 of biologically derived pigments. Whether this is true or not will have 



to be decided by the investigations of the future. 



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