2=s6 WHALES 



# ORAMGE 



# GREEM 



Figure 132. Krill, a small crustacean of the species Euphausia superba Dana is the main 

 food of large Rorquals in the Antarctic. {Modified after Mackintosh and Wheeler, igsg.) 



deep down as was once believed. The reason why they sound as far down 

 as they do is, therefore, something of a mystery (see Chapter 4) . 



Fresh krill presents a very colourful spectacle since the green of much 

 of its thorax provides a striking contrast with the orange head, appendages 

 and abdomen. The green colour is due to the stomach usually being filled 

 with unicellular diatoms, particularly with Fragilariopsis antarctica (Fig. 

 1 33) . Diatoms, as we might have guessed from their colour, are unicellular 

 plants which like all plants contain chlorophyll, whereby carbonic acid 

 dissolved in the sea can be photosynthesized into organic matter. Diatoms 

 store this food in the form of small droplets of fat, and it is by and large 

 the fat of these microscopic Antarctic diatoms which, after they have 

 successively passed through krill, whales and finally the factories, we buy 

 as margarine or soap. 



Because photosynthesis can only take place under the influence of 

 sunlight which, as we have seen in Chapter 9, cannot penetrate to lower 

 reaches of the ocean, diatoms, and hence krill, are mainly found near the 

 surface of the sea. 



The orange colour of so many crustaceans arises from the presence of 

 carotene, another substance found predominantly in plants, and largely 

 responsible for the orange colour of carrots. Krill must therefore have 

 derived its carotene, too, from diatoms. Carotene is also present in other 

 planktonic organisms such as worms, snails and small jellyfish, and in 

 the Antarctic a plankton net usually comes up with a rich orange hai'vest 

 glittering through vitreous bodies. Carotene is a particularly important 

 pigment since it is the precursor of vitamin A which is so abundant in the 

 liver of whales and to a lesser extent in their blubber. Apart from carotene, 

 krill contains so much fully synthesized vitamin A, particularly in the eyes, 

 that whales have no need to convert krill carotene into vitamin A, their 

 needs being fully met as it is. We shall return to this subject in greater 

 detail in Chapter 11 which deals with the liver; here, we shall merely 

 point out that it is because of the presence of carotene that the contents 



