5 GEORGE V. SESSIONAL PAPER No. 39b A. 1915 



VIII. 



CONTRIBUTIONS TO THE LIFE HISTORY OF PROTEOCEPHALUS 



AMBLOPLITIS LEIDY. 



A Parasite of the Black Bass. 



By A. R. Cooper, M.A., University of Toronto. 



(Plates XIX— XXI) 



During the summer of 1909 the writer began a systematic study of the parasites 

 infecting fresh-water fishes of the Georgian Bay region. In the course of this 

 work it was noticed that the visceral organs of the small-mouthed black bass 

 were greatly infected with the plerocercoids of some species of Proteocephalus. 

 Up to that time Leidy's description of Tcenia micropteri was the only reference to 

 plerocercoids found in the bass, so that it was thought that these were individuals 

 of that species. Furthermore, there appeared to be a close resemblance between 

 the scolex of this form and that of P, ambloplitis Leidy, which was found in the 

 intestinal tract of the same host, consequently a comparative study was undertaken 

 to find out whether the resemblance was sufficient to warrant the view that the 

 former was a larval stage of the latter. In order to ascertain the local distribution 

 of the infection, adult hosts ranging in length from 22-23 cm., were taken in differ- 

 ent localities around the Lake Biological Station on Georgian Bay, from the out- 

 lying islands and reefs some miles from shore inwards to the inland lakes and the 

 Go Home River. The present paper is devoted chiefly to a description of certain 

 stages of these plerocercoids and their identification with P. ambloplitis, but a 

 number of observations on the life-history of this species have also been appended. 



As a rule, bass of small size caught inshore are not greatly parasitized by P. 

 ambloplitis, only occasionally is a young one found to contain a number of individ- 

 uals of this species. Large bass, on the other hand, are invariably much infected. 

 It is probable that the harboring of even a dozen or more adult specimens of this 

 worm would have no noticeable effect on the fish in view of the presence of scores 

 and even a hundred or more of echinorhynchi which are found in the pyloric 

 cceca and intestines of every adult bass one examines. Of a small lot of bass 

 caught near a group of islands lying about three miles from the mainshore, three, 

 averaging 26 cm. in length, were examined for parasities, and in only one of these 

 were adult specimens of P. ambloplitis, to the number of nine, found in the stomach. 

 On the other hand the plerocercoid above-mentioned, which will be called P. 

 micropteri Leidy (LaRue, '11) was well represented. In ten bass from twenty-one to 

 to twenty-nine ,centimetres in length, only three harbored adults (P. ambloplitis) 

 namely, two, each ten centimetres long when extended, in the first bass; two, 

 thirty-three and ten centimetres, respectively, in the second; and three much smaller 



