SUMMARIZED OBSERVATIONS 371 



SOUTH SHETLANDS, JANUARY, 192S 



During this month a few observ'ations were made by Mr Fraser and his colleagues, while awaiting 

 transport to South Georgia, on whales brought to Deception Island. The presence or absence 

 of diatoms was noted upon 24 Fin whales and three Blue whales. Diatoms were recorded on 18 

 whales and thick or extensive film on 1 1 . Thus the percentage infection was 66-7, and the percentage 

 with thick film 40-7. The numbers are obviously too small to warrant any more detailed treatment. 



ICE-EDGE TO THE SOUTH OF AFRICA, 1932-3 



Mr Laurie was able to collect some fifty scrapings during this season in the S.S. 'Southern 

 Princess ', but as this represented only a small fraction of the catch, no attempt has been made to 

 work out the seasonal variation in percentage infection. Nevertheless this collection indicated a 

 steady increase in infection throughout the season, as would be expected from the more detailed 

 work in other areas. It was very interesting to find the Blue whales far to the south of the African 

 Continent infected by the identical diatom species, Cocconeis ceticola, so common in the Falklands 

 sector of the Antarctic. The individual frustules appeared to be slightly larger, on an average, and 

 ver)- slightly narrower in proportion to their length. In all other respects no difference could be 

 detected. All but one of these samples were obtained from Blue whales. Spore formation was 

 commoner than at South Georgia, particularly at the beginning and end of the season. A feature 

 of great interest was the occurrence in a majority of the scrapings of large numbers of the ciliate 

 protozoan described and figured by Mackintosh and Wheeler (1929, p. 377). Later observations 

 by Dr Wheeler led him to believe that the presence of this ciliate on the South Georgian whales 

 was probably accidental, as he found it living in the water round the whaling station. Mr Laurie's 

 collection seems to indicate that it may be a common external parasite of whales, for the ' Southern 

 Princess ' was working in the open ocean many miles from land. In some of the scrapings ciliates 

 which had apparently ingested some of the diatoms were found. 



THE SEASONAL VARIATION IN PERCENTAGE INFECTION 



From the monthly observations summarized in the last section, it became clear that 

 a considerable difference in the percentage infection of the two sexes of Blue and Fin 

 whales occurred. In the sixteen month groups studied the percentage infection of Fin 

 males exceeded that of Fin females on all but two occasions — in November 1928 and 

 December 1929. The figures for Blue whales are not so reliable owing to the greater 

 fluctuations in the catch of this species at South Georgia. Out of fourteen month groups 

 the percentage infection of Blue males exceeded that of Blue females on nine occasions, 

 but on four of these the excess was slight. The conclusion reached is that while the 

 behaviour of the two sexes in the Fin whale must differ considerably on the South 

 Georgian grounds, that of the Blue whales is more uniform. A majority of the Blue 

 whales are probably on passage to and from other feeding grounds farther south, and a 

 large proportion of the Fin whales taken during the second half of the season are im- 

 mature. The evidence of the skin-diatom infection suggests that the schooling habit is 

 strongly developed among the immature males. 



Considering the seasonal variation in percentage infection of the two species it is at 

 once apparent that diatoms are more common on Fin whales than on Blue, except at the 

 end of the season when the Blue whales captured are almost certainly on their way north. 



