EXTERNAL PARASITES OF WHALES 373 



EXTERNAL PARASITES 



The species of external and internal parasites of whales will be dealt with in separate 

 papers. They have not been thoroughly examined at the time of writing and are there- 

 fore dealt with only very briefly here. The greater part of this section is devoted to an 

 account of certain scars, of which the origin is rather obscure, but which are probably 

 to be attributed to a parasite or parasites of some kind. 



The external parasites of whales are mostly crustaceans, and the commonest internal 

 parasites are tapeworms and Acanthocephala. 



The following external parasites have been collected from Blue and Fin whales 

 (apart from certain more or less minute forms found on the baleen) : 



Cirripedia. Copepoda. 



Coromtla regina. Pennella sp. 



Conchoderma auritutn. Amphipoda. 



C. virgatum. Cyamiis sp. 



XenobalaJius globicipitis. Diatoms. 



Ectoparasites in general are rarely found on Blue and Fin whales at South Georgia. 

 Infection seems to take place more easily in the warmer waters of the South African 

 coast, where Pennella is particularly common. At South Georgia such external parasites 

 as do occur are generally fully grown, while those observed at South Africa included, 

 at any rate in the case of Coronula and Pennella, young ones in all stages besides the 

 fully grown individuals. It appears that whales become infected with these external 

 parasites during their stay in the warmer waters, but lose them on migrating to the 

 colder waters of the south. The film of diatoms is the only exception to this, for it is 

 undoubtedly contracted in the summer in the Antarctic or sub-Antarctic waters. 

 Early in the season it may be seen in its initial stages in the form of little round green 

 patches on the skin, an inch or so in diameter. These patches appear to be growing 

 colonies, which gradually expand from numerous centres and eventually cover perhaps 

 the whole body within a few months. These diatoms were described by Bennett (1920) 

 and identified by Nelson (1920) as a species of Cocconeis. 



The ability of a whale to throw off the Pennella which most commonly attack Blue 

 and Fin whales, seems to have some physiological significance, for it is often found 

 that a whale taken at South Georgia with a number of these parasites in its blubber is 

 suffering from some internal growth or disease. 



Internal parasites are to be found more commonly than the external Crustacea, and 

 they are often present in great numbers in whales from both South Georgia and South 

 Africa. Blue whales are more often parasitized than Fin whales, in fact more than half 

 the individuals of the former species from both localities contain tapeworms or Acantho- 

 cephala or both in their intestines. In both species the younger whales are normally 

 more heavily infected than the older ones. 



We may now turn to an account of a kind of disease to which all southern Blue and 

 Fin whales seem to be subject. All the whales of these species caught at South Georgia 

 are marked by numbers of whitish scars which are very difli'erent in appearance from 



