CHAPTER XIV 

 A SIMPLE LIFE CYCLE OF A SPOROZOAN 



TECHNICAL SUGGESTIONS 



The species of Monocystis from the seminal vesicles of the earth- 

 worm, on account of their availability and the readiness with which 

 the various stages can be found, afford a most satisfactory intro- 

 duction to the study of the Sporozoa. 



In most localities the great majority of the large Lumbricus terrestris 

 will be found infected. In regions where this worm is not estab- 

 lished, it is desirable to purchase living specimens from some Eastern 

 collector or through supply houses. In case this species is not 

 obtained, local species will usually be found to harbor related para- 

 sites, as shown by Mickel, 1925, who found Helodrilus caliginosus in 

 Minnesota heavily infested by Zygocystis cometa. 



For supplementing the study of fresh materials, sections and smear 

 preparations should be prepared from heavily infected specimens. 



Grasshoppers, cockroaches, and the much-used mealworms (larva' 

 of Tenebrio molitor) are certain sources of cephaline gregarines. The 

 mealworms can be purchased from bird dealers if a supply is not kept 

 in the laboratory. 



CHARACTERISTICS OF THE GREGARINIDA 



The class Sporozoa is a somewhat heterogeneous group of 

 Protozoa, made up of forms exclusively parasitic, which lack 

 definite locomotory organs, mouth, anus, and contractile vacuoles. 

 They produce at some stage in their life history resistant spores 

 which, however, are not directly infective but give rise to 

 sporozoites which are the forms infecting new hosts. 



The order Gregarinida includes ccelom-inhabiting Sporozoa 

 which reproduce typically by spore formation after the fertilizing 

 union of similar gametes. They arc very common as parasites 

 of invertebrates, chiefly insects, but the majority of the species 

 are probably harmless to their hosts. Dissemination is usually 

 passive, infection being by way of the alimentary canal. 



In spite of their relative unimportance as parasites, the 

 generalized life cycle of the Gregarinida and their close relation- 

 ship to important groups of mammalian and human parasites 



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