PHYLUM PROTOZOA. ONE-CELLED PARASITES 



55 



sitic species that had free-Hving ancestors. 

 The origin of the Sporozoa is obscure. The 

 different groups included in the class may 

 have arisen from different classes. Those 

 with amoeboid sporozoites may have evolved 

 from amoeboid ancestors, and those with 

 flagellated sporozoites from flagellate an- 

 cestors. Coccidia probably originated from 

 gregarines and the blood-inhabiting Haemo- 

 sporidia from the Coccidia. 



CLASSIFICATION OF 

 THE SPOROZOA 



(For reference purposes only) 



Class Sporozoa. These are among the most 

 widely distributed of all animal parasites; mem- 

 bers of almost every large group in the animal 

 kingdom are parasitized by one or more species. 

 They are greatly modified, due to their para- 

 sitic existence. These modifications have re- 

 sulted in the absence of locomotor organelles, 

 mouth, anal pore, and contractile vacuoles. 

 Food is absorbed directly from the host, and 

 respiration and excretion take place by diffu- 

 sion through the cell membrane. Many organs 

 of the host may be parasitized, especially the 

 digestive tract, kidneys, blood, muscles, and 

 connective tissues. The 4 subclasses and 5 

 orders are as follows: 



Subclass 1. Telosporidia. Spores produced 

 at end of life of trophozoite; no 

 polar capsule nor polar filament. 



Order 1. Gregarinida. Common parasites 

 of insects; at first intracellular, 

 but later often free in cavities. 

 Ex. Monocystis lumbrici (Fig. 

 23). 



Order 2. Coccidia. Parasites of verte- 

 brates and invertebrates; one 

 species in man. Ex. Isospora 

 hominis (Fig. 24). 



Order 3. Haemosporidia. Parasites in 

 blood cells of vertebrates, and 

 in bodies of invertebrates. Ex. 

 Malaria organisms of man (Fig. 

 33, p. 69). 

 Subclass 2. Cnidosporidia (Gr. knide, net- 

 tle). Spores with one to four 

 polar capsules, with a coiled 

 polar filament. 



Order 1. Myxosporidia. Principally para- 

 sites of fish. Ex. Myxidium lie- 

 berkuhni. 



Order 2. Microsporidia. Spores extremely 

 small; usually with one polar 

 capsule; insects most frequently 

 infected. Ex. Nosema apis, and 

 Thelohania contejeani. 

 Subclass 3. Acnidosporidia. Simple spores 

 without polar capsules; some 

 parasitic in vertebrates. 

 Subclass 4. Haplosporidia. In lower verte- 

 brates and invertebrates. Ex. 

 Haplosporidium nemertis. 



