The Oestoda of the Scottish National Antarctic Expedition. Bv John Rennie, 

 D.Sc, and Alexander Raid, M.A., University of Aberdeen. (Witli Two 

 Plates.) 



(MS. received May G, 1912. Read June 17, 1912. Ls.sued separately September 6, 1912.) 



The Cestode material obtained by the Scotia Expedition consisted of eight adult 

 and three larvaj or immature forms. Of these, one {Anchistrocephcdus microcephalus, 

 Rud.) is not Antarctic, having been obtained from the Sunfisli {Orthagoriscus mola), at 

 Station 107, in 39 12' S., 53" 44' W., on January 1, 1903. 



Of the others, only two appear to have been previously described, viz. i)^■6of/«•tocep/ia^ts 

 antarcticus, Baird, and Dibolhrioceplmlus wllsoni, Shipley. The hosts from which the 

 Cestoda of the Antarctic and sub-Antarctic regions were obtained are, with the exception 

 of the Bonito,* from which a larval Tetrarhynclms was obtained. Seals and Penguins. In 

 view of this fact, the number of forms obtained may be regarded as relatively large. A 

 study of the species on record from Arctic Pinnipedia suggests the interesting fact that 

 the two Cestode faunas are quite distinct. Eight species of Dihothriocephalus are on 

 record from Pinnipedia of the Arctic regions, none of which have so far been obtained 

 in the Antarctic. The adult forms found, however, with one exception all belong to 



this genus. 



A noteworthy feature is the relatively large proportion of very small and delicate 

 species of Cestoda occurring in the Pinnipedia of the Antarctic. Indeed, none of the 

 forms obtained can be described as large ; the maximum size is that of D. pygoscehs, 



viz. 29 cm. 



Shipley has suggested with regard to the Cestoda of Ross's Seal that, in view of the 

 feebleness and variability of its dentition, it probably feeds on soft substances, and 

 expresses the opinion that the plerocercoid stage probably occurs in the tissues of 

 Cephalopods. Jellyfish are also mentioned, and these form part of the food of this Seal. 



With regard to Seal Cestodes in general, we note that although the parasites are 

 small the infection is generally heavy, and from this it may be argued as probable that 

 the intermediate hosts become infected without much difficulty. The embryos are 

 extraordinarily minute, and if dissipated in the waters would probably infect drifting 

 organisms, e.g. Jellyfish or Ctenophora, more readily than others, e.g. Fishes. On the 

 other hand, Crustacea and similar organisms of scavenging habits, feeding on the t:eces 

 of the Seals, have an even better chance of being infected, and these may provide the 

 intermediate host. Beyond this it is scarcely profitable to speculate further. 



* This flsh {Thynnus pelamys Linn.) it appears was found at Station 31-some distance south of the Cape Verde 

 Islands-on 4th December 1902, and its parasite therefore cannot be described as Antarctic or sub-Antarctic. 



(REPRINTED FROM THE TRANSACTIONS OK THE ROVAL SOCIETY OF EDINBURGH, VOL. XLVIII., PV. 441-453.) 



