ON A MYXOSPORIDIUM INFESTING AUSTRALIAN FROGS. 337 



7.— ON A MYXOSPORIDIUM INFESTING AUSTRALIAN 



FROGS. 



By A. W. Fletcher, B.A., B. Sc, Sydney. 



[Abstract.'\ 



This organism is a parasite Sporozoan, and was first observed in 

 the testes of a considerable proportion of the male specimens of 

 Ilyfa aurea dissected in the Biological Laboratory of the Sydney 

 University. It is found to have its seat in the urinary bladder 

 of male and female under the peritoneum, and in the testes. When 

 well developed, it presents a large oolitic mass of encysted 

 myxosporidia, the presence of which causes the pleuro-peritoneal 

 cavity, especially tliat of a female charged with ova, to be distended 

 to an abnormal extent. The myxosporidium of the Australian 

 Frog is found to infect, as yet, only one species, viz., Hyla aurea. 



Hitherto, the myxosporidia have only been found parasitic in 

 fresh-water fish and certain Elasmobranchs. But they have not 

 previously been observed in any of the Australian fauna. 

 Biitschli has described an amoeboid myxosporidium from the 

 pike's urinary bladder, and an encysted myxosporidium from the 

 gills of the Cyprinoidea, this latter bearing a striking resemblance 

 to that of the Australian frog. The myxosporidium from the frog 

 presents a number of cysts containing myriads of microscopic 

 spores. Each spore is flattened, oval, bivalvular, ^^t\\. inch in 

 its greatest length. It contains a nucleated mass of protoplasm and 

 two polar bodies or germs, each having coiled up within it a spiral 

 thread which is shot out on the application of alkalis or con- 

 centrated II2S04 



By the use of iodine the internal contents and firm capsule of 

 the spore are well differentiated, while the nucleus is stained a 

 bright red. Several free germs with attached threads were 

 observed ; they were probably released by pressure. Different 

 abnormal adult forms were seen, one spore being pointed ; 

 also several intermediate stages between germs and spores. As 

 regards the life-history, the myxosporidium probably develops in 

 the endoplasm atrinucleate protoplasmic globule, two of the nuclei 

 becoming eventually the germs, while the third forms the general 

 protoplasmic contents of the spore. But the actual successive 

 steps in the development of the germs from these nuclei have not 

 yet been fully worked out either by Biitschli in the myxosporidiu^^\ Q 4 / 

 of the Cyprinoidea, or in the case of the Austi-alian Frog. / O ','•.." . ,^ <! 





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A F. 



