Chapter 26 

 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. 448) 



Order 1 Sarcosporidia Balbiani 



These sporozoans are characteristic muscle parasites of mam- 

 mals, although reptiles and birds have also been found to harbor 

 them. The spore which has been known as Rainey's corpuscle, is 

 crescent-shaped (Fig. 205). One end is rounded and the other 

 pointed. Near one end there is a single nucleus, and the cytoplasm 

 contains numerous 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 liberated, which enters the gut-epithelium. After 

 multiplying in this situation, the organism makes its way into the 

 muscular tissue. At the beginning the parasitic mass is an elon- 

 gated multinucleate body which may or may not divide into as 



Fig. 204, a, Sarcocystis tenella in the oesophagus of sheep; b, S. 

 niiescheriana in the muscle of pig; Xl (Schueidemiihl from Doflein). 



many uninucleate bodies as there are nuclei. 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 (Fig. 205). Some authors believe that the 



446 



