Chapter 27 

 Subclass 2 Acnidosporidia Cepede 



THE sporozoa which are provisionally grouped here are mostly 

 incompletely known, although some of them are widely dis- 

 tributed among the higher vertebrates. They possess spores which 

 are quite simple in their structure, while their development is so 

 far as is known wholly different from that of the Telosporidia. 



Muscle parasites of higher vertebrates Order 1 Sarcosporidia 



Parasites of invertebrates and fish Order 2 Haplosporidia (p. 510) 



Order 1 Sarcosporidia Balbiani 



These sporozoans are characteristic muscle parasites of mammals, 

 although reptiles and birds have also been found to harbor them. 



Fig. 238. a, Sarcocystis tenella in the oesophagus of sheep; b, S.miescheri- 

 ana in the muscle of pig; Xl (Schneidemiihl from Doflein). 



The spore which has been known as Rainey's corpuscle, is crescent- 

 shaped (Fig. 239). One end is rounded and the other end is bluntly 

 pointed. There is a single nucleus and the cytoplasm contains numer- 

 ous granules. Infection of a new host begins with the entrance of 

 spores into the digestive tract of a specific animal through mouth. 

 The delicate spore membrane ruptures and the sporozoite is liber- 

 ated, which enters the gut-epithelium. After undergoing certain de- 

 velopment which is still unknown, the organism makes its way 

 through blood stream (?) into the muscular tissue. At the beginning 

 the trophozoite is a small uninucleate body, but develops, by divi- 

 sion and growth, into an elongated multinucleate body which then 

 ordinarily divide into many uninucleate bodies. These become the 

 centers of infection in other muscle fibers. Some trophozoites grow 

 in size and the body becomes divided into parts, in each of which 

 spores are formed. Some authors believe that the spores themselves 

 are capable of fission. The host muscle fiber harboring the trophozoite 



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