478 



THE BIOLOGY OF MARINE ANIMALS 



The intestine and digestive glands of some molluscs and Crustacea, and 

 the digestive caeca of asteroids and other echinoderms, contain greenish 

 pigments known generally as hepatochlorophyll and probably consisting 

 of a mixture of chlorophylls and chlorophyll derivatives. Vegetal chloro- 

 phyll undergoes a certain amount of degradation in its passage through the 

 animal. The viscera of a tectibranch mollusc Akera yield phaeophorbide, 

 which is formed from chlorophyll contained in the algal food. Proto- 

 porphyrin, occurring in the integument of Asterias rubens, may be derived 

 from chlorophyll pigments present in the hepatic caeca (43, 45). 



Some examples of colours due to haem-containing respiratory pigments 

 have been mentioned previously. Concentrations of myohaemoglobin 



Green algal 

 (flagellate) cells 



Muscle masses 

 CO.) 



Fig. 11.2. Intestinal Coloration of Chaetopterus variopedatus 



(a) Transverse section through the mid-body ; the dark green intestinal wall is shown 

 in heavy black; (b) epithelial cells of the intestinal wall with pigmented spherules. (After 

 Lankester, 1897-98.) 



sometimes bring about marked differences between red and white muscles ; 

 for example, in the teleosts Luvarus and Hippocampus. In the polychaete 

 Myxicola infundibulum chlorocruorin imparts a greenish tint to the inner 

 layers of the animal's tube. Haemochromogens are widely distributed in 

 the gut lumen of molluscs and polychaetes (24, 70). 



The decomposition of haemoglobin gives rise to the bile pigment 

 biliverdin through the rupture of the porphyrin nucleus and the release of 

 iron, and this or related bile pigments are responsible for some animal 

 colours. The ragworm Nereis diver sicolor is variable in colour, different 

 individuals being orange, brown or green. The orange and brown colours 

 are due largely to carotenoids, but the green pigment is biliverdin formed 

 by the breakdown of haemoglobin. The granules of biliverdin occurring in 

 the body wall are ultimately transferred to the gut and excreted. Males, on 



