3 1 2 Sporozoa 



although a given species may be limited to a particular tissue. Some of 

 these infections are frequently fatal to the hosts. 



The life-cycles show certain general features, although details vary to 

 some extent. The zygote is formed by the fusion of two haploid sporoplas- 

 mic nuclei, commonly during the dispersal of spores to new hosts (99). 



Fig. 6. 26. A. Spore of Myxobolus osburni Herrick, showing two polar 

 filaments (coiled in capsules) and sporoplasm containing an iodinophilous 

 vacuole; x2250 approx. (after Otto and Jahn). B. Spore of M. osburni, 

 sutural view shov.'ing the two valves and the sutural ridges (after Otto 

 and Jahn). C. Extruded polar filaments, spore of Leptotheca ohhnacheri 

 (Gurley) Labbe; xll75 (after Kudo). D. Amoeboid trophozoite of L. 

 ohlmacheri containing two spores; xl880 (after Kudo). E. Spore of Sphaer- 

 actinomyxon gigas Granata, polar view showing the three valves charac- 

 teristic of spore membranes in the Actinomyxida; the three polar capsules 

 are indicated in solid black; x850 (after G.). F. Trophozoite of Myxobilatus 

 asymmetricus Davis, attached to epithelium of urinary bladder (fish); 

 several developing sporoblasts are present; the free end of the trophozoite 

 is covered with delicate bristles of uncertain significance; xSOO (after D.). 



After ingestion, the zygote escapes from the spore membrane and migrates 

 to the tissue or body cavity in which development will occur. The growth 

 phase includes both nuclear division and cytoplasmic growth. Depending 

 upon the species, reproduction by plasmotomy (13), or by endogenous or 

 exogenous budding may occur, particularly in monosporous and dispo- 

 rous species (99). If buds are produced, they may repeat the reproductive 



