ON THE DIATOMS OF THE SKIN FILM OF 



WHALES, AND THEIR POSSIBLE BEARING 



ON PROBLEMS OF WHALE MOVEMENTS 



By T. John Hart, M.Sc. 

 (Plate XI; text-figs. i-8) 



INTRODUCTION 



PREVIOUS WORK 



THE observation that the skins of Southern Bhie and Fin whales, within the zone 

 of Antarctic surface water, are sometimes invested with " a yellow slime, apparently 

 due to algae" was first made by the late Major G. E. H. Barrett-Hamilton when 

 working on the whales brought into Leith Harbour, South Georgia, during the season 

 1913-14 (Hinton, 1925, pp. no, 137). Later Mr A. G. Bennett independently observed 

 that a similar investment was frequent upon the whales captured on the South Shetland 

 grounds. He also noted that the constituents of the film appeared to be diatoms, and 

 this was fully confirmed by Mr E. W. Nelson in an appendix to Bennett's paper (1920, 

 p. 354). Bennett (p. 353) made the important observation that the whales most heavily 

 infected with diatoms were those which from the thickness of their blubber might 

 reasonably be assumed to have spent some time within the Antarctic Zone; while a 

 majority of the lean individuals, recent arrivals from warmer waters, were noticeably 

 free from diatom film. The resemblance of the colouring on the lighter underparts of 

 the whales to the yellowish bands so common on polar sea-ice at about water-level, 

 which have long been known to be caused by the presence of diatoms, was also noted 

 by Bennett. He concluded that the whales only became infected in Antarctic waters, 

 and that by a study of the diatom species on their skins, and of those upon the sea-ice, 

 it might be possible to gain some insight into the movements of the whales. The first 

 part of this conclusion is undoubtedly correct, but since the predominant diatom of the 

 skin film, Cocconeis ceticola. Nelson, is not known from any other habitat, the extent to 

 which the disposition of the skin film can be used as an index to whale movements is 

 strictly limited. 



The directions in which Bennett's observations could most usefully be followed up 

 are admirably expressed in Nelson's appendix to the former's paper already quoted, and 

 from the outset of the Discovery investigations, data concerning the skin film of the 

 whales brought in to Grytviken Harbour, South Georgia, have been collected by the 

 officers engaged at the Marine Biological Station. The chief points derived from these 

 data during 1925-7 have been briefly summarized by Mackintosh and Wheeler (1929, 

 pp. 372, 373). They found it impossible to say much concerning the correlation between 

 fatness and diatom infection. Small spots of film were observed on some whales 



