General Morphology of the Protozoa 35 



Pigments 



The pigments of chromatophores vary in different groups of the 

 phytoflagellates, and may have some phylogenetic as well as taxonomic 

 significance. Chlorophyll of one variety or another presumably is always 

 present although the green color may be masked by other pigments to 

 produce shades of greenish-yellow, yellow, brown, and rarely blue. Blue 

 chromatophores have been reported (143) in Cyanomonas coeruleus, 

 Chroomonas setoniensis, Cyanomastix morgani, and Gymnodinium lim- 

 netician. 



In addition to the pigments of chromatophores, various red, yellow, 

 violet, brown, blue, and green pigments are found in the cytoplasm of 

 certain Protozoa, many of them species without chromatophores. The 

 blue-green granules ("stentorin") of Stentor coeruleus, which contain 

 lipoproteins and resemble mitochondria, lie mainly in longitudinal ecto- 

 plasmic bands. These granules usually disappear after 24-48 hours of 

 starvation (223). The pink pigment of Blepharisma undulans, which is 

 also peripheral (169), is bleached after exposure to light, and is regen- 

 erated in darkness (69). This pigment is quite toxic to species of Para- 

 mecium, various other ciliates, and also to rotifers (70). 



Chromatographic techniques (18, 204, 205, 206) have been used in the 

 identification of certain pigments. In Dinoflagellida, chlorophylls a and 

 c, ^-carotene ("yellow haematochrome"), and several xanthophylls (di- 

 noxanthin, diadinoxanthin, neodinoxanthin, peridinin) have been dis- 

 tinguished. Peridinin, which may be limited to dinoflagellates among the 

 Protozoa, is possible identical with sulcatoxanthin isolated from certain 

 sea anemones and probably derived from their symbiotic algae (82). 

 Chrysomonadida contain chlorophyll a (but apparently no chlorophyll 

 b), ^-carotene and the xanthophyll, lutein. Euglenida contain chloro- 

 phylls a and b, ^-carotene and also red haematochrome (euglenarhodon), 

 a xanthophyll closely related to the astacene of Crustacea. Phytomonadida 

 contain chlorophylls a and b and, in such species as Haematococcus plu- 

 vialis, a red haematochrome similar to that of Euglenida. 



The functional significance of most protozoan pigments is unknown. 

 The absorption of energy in photosynthesis is, of course, dependent 

 mainly upon the chlorophylls, of which chlorophyll a is probably most 

 important. However, carotenoid pigments also may serve in absorbing 

 the predominantly blue-green light of low intensity received by marine 

 species in fairly deep water (50, 205). The red pigment of Euglejia rubra 

 may be protective in reflecting light from the red end of the spectrum. 

 This species thrives in shallow water reaching a temperature of 35-45° 

 in bright sunlight. Under such conditions the pigment forms a layer 

 just outside the chromatophores (107). In the laboratory, peripheral 

 migration of the pigment occurs at temperatures of 30-40° in either dark- 



