NOTES ON THE FLESH PARASITES OF MARINE FOOD FISHES. 



By EDWIN LINTON, Ph. D., 

 Professor of Biology, Washington and Jefferson College. 



INTRODUCTION. 



In beginning the study of fish parasites it was soon realized that by far 

 the most Hkely place to find entozoa is within the body cavity of the host. 

 Often, therefore, on account of the abundance of material and the limited time 

 at my disposal, I confined my collecting almost wholly to what could be secured 

 from the alimentary tract and the body cavity. An occasional search for para- 

 sites in the flesh of marine fishes met with so few finds that it came to be in 

 large measure neglected. In 1904, however, I discovered that the parasitism 

 which I had already noted in the case of the butterfish {Poronotus triacanthus) , 

 instead of being of occasional and accidental occurrence, is really of almost 

 universal prevalence in all localities where I have studied this fish. 



The results of my investigations on the butterfish parasite naturally sug- 

 gested inquiry as to the condition in this particular of other food fishes, and it 

 is the purpose of this paper to set forth some of the results of my investigations 

 of this subject. In the summer which has just passed (1908) I spent three 

 weeks at the laboratory of the Carnegie Institution at the Dry Tortugas, and 

 the remainder of the time at the laboratory of the Bureau of Fisheries, Woods 

 Hole, Mass. Most of the fishes that I examined were examined for flesh para- 

 sites, and, with one or two exceptions, this paper is confined to results obtained 

 in the present season. This applies more especially to the tabulated results. 



The results of this study are as yet very uneven; at the same time they 

 afford certain conclusions which are of importance, as will appear in the progress 

 of the paper. It may be stated properly in this connection that while very 

 few, or even in some cases only one, example of a species of fish was examined, 

 the general results of this past summer's investigation are in agreement with 

 those of previous years — namely, that the marine food fishes, with the excep- 

 tion of the butterfish, are singularly free from parasites in the flesh. Indeed, 

 with the exception of the butterfish, I have not yet found any one of our food 

 fishes which is more than an accidental intermediate host for any parasite. At 

 least, if there are any such they are confined to those cases in which the walls 



of the alimentary tract furnish a lodgment for various cestode cysts. 



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