568 



PROTOZOOLOGY 



division within the host body; multiplication within cyst which is 

 formed after dropping off the fish skin and in which numerous (up to 

 1000) ciliated bodies (30-45^ in diameter) are produced; conjugation 

 has been reported; parasitic in the integument of freshwater fishes; 

 in aquarium, host fish may suffer death; widely distributed. 



Fig. 270. Ichthyophthirius multifiliis. a, free-swimming individual, X75 

 (Butschli); b-e, development within cyst; f, a young individual, X400 

 (Fouquet); g, section through a fin of infected carp showing numerous 

 parasites, XlO (Kudo); h, a catfish, Ameiurus albidus, heavily infected by 

 the ciliate (Stiles). 



/. multifiliis F. (Fig. 270). 100-1000^ long; ovoid; produces pus- 

 tules in the epidermis or gills; cytostome is large, 30-40/i in diameter. 

 Pearson (1932) and Kudo (1934) reported extensive infections in 

 large open ponds in Indiana and Illinois. MacLennan (1935, 1937) 

 observed that the grown trophozoites leave the host epithelium and 



