2o8 BULLETIN OF THE BUREAU OF FISHERIES. 



PREVALENCE OF MYXOSPORIDIAN INFECTION IN FISH. 



The infection of muscle tissue by Myxosporidia is quite common in fish. A parasite 

 belonging to the genus Chloromyxum occurs in the flesh of the young herring and young 

 alewife (Linton, 1891). Both the pansporoblast and spores of a Chloromyxum. have been 

 found abundantly by the writer inside the fibers, and the spores also assembled else- 

 where in large cysts. A fuller account of this species will be published later. The 

 muscle cells of Callionymus lyra are also subject to an intracellular parasite (Glugea 

 destruens Thelohan, 1891; Henneguy et Thelohan, 1892; Gurley, 1893), the myxoplasm 

 of which has not been observed. It causes the muscle fibers to undergo degeneration. 

 Chloromyxum qiiadratum (Thelohan, 1894) also occurs in the muscles of this fish. It is 

 also reported in the flesh of Coris julis, Syngnaihus aciis, Trachurus irachurus (Minchin, 

 1903) and Nero phis (equoris. In Cottus scorpio the muscle tissue is attacked by Pleisto- 

 phora typicalis (Thelohan, 1890, and 1891 ; Gurley, 1893). Both pansporoblast and spores 

 have been found, but they are intercellular in position. The muscle fibers are displaced 

 but do not degenerate. Leptotheca perlata (Gurley) occurs in the muscles of Acerina 

 cernua Linnseus. Of these species there are none that closely resemble M. musculi. 

 Numerous cases of Myxoboli are known to inhabit gill tissues. Auerbach (191 1) Hsts 

 22 species of Myxobolus which have been described in the gills of fish. But we have 

 encountered nothing that might be considered identical to M. musculi. 



The disease of Fundulus is remarkably like that which has so frequently caused 

 epidemics amongst the barbel (Barbus harbus Linnseus) of European rivers. The latter 

 is caused by M. pfeifjeri Thelohan (Raillet, 1890; Ludwig, 1888; Thelohan, 1894). It 

 produces both tumors and ulcers and occurs encysted and free in muscle, liver, kidney, 

 spleen, and connective tissue. The tumor when formed does not at all times break 

 through, either into the body cavity or to the outside. It is not an integumentary 

 parasite at the beginning as those of Fundulus seem to be. The tumor commonly occurs 

 amongst the connective tissue and the muscles of the body wall. The parasite may be 

 encysted in a thin restraining membrane produced by the host. Numerous individuals 

 of about the same age tend to gather in groups and become isolated in tube-like cysts. 

 The muscle fiber is invaded and undergoes a "vitreous alteration" (Thelohan, 1893) 

 leaving "yellow granulations as degeneration products" (KeysseUtz, 1908). Thelohan's 

 figure 5, plate vii (Thelohan, 1894), representing a muscle fiber containing myxoplasms 

 in transverse crevices recalls, very vividly the appearances we have encountered in the 

 degenerate muscle of Fundulus (fig. 4, pi. xx). The tumors may soften and become a 

 "stinking abscess containing spores" (Ludwig). M. pfeifferi passes through distinct 

 cycles of development which is no doubt the case in M. musculi. In April it is in a vege- 

 tative stage in which the multiplicative reproduction prevails; later propagative repro- 

 duction is encountered and myxospores are developed. The rate of advance of the dis- 

 ease depends upon the temperature (Keysselitz). 



Both Kej'sselitz and Thelohan describe bacteria in tissues of diseased barbel. 

 Keysselitz says bacteria contribute liberally to the formation of the tumors. These 

 bacilli are found only in the tissues infected b\' Myxosporidia. They prevent the 

 growth of connective tissue and bring about degeneration (gangrene) of the tissue. 

 These bacilli are "as long as the spore" (Pfeiffer, 1890) (6/(, Thelohan) and stain easily 

 with methylene blue and gentian violet. (This is also true of the bacilli of Fundulus 



