748 



OKDER: MICROSPORIDIIDA 



Microsporidiida of Blood-Sucking Arthropoda and Nematoda. 



As already remarked, the Microsj^oridiida are parasites chiefly of Arthro- 

 poda, and some of the forms which may be encountered in experimental 

 work will be considered briefly. It is important to remember these 

 organisms when insect flagellates are being studied. They may be con- 

 fused very readily with the minute leishmania forms of certain flagellates, 

 as pointed out by Chatton (1911a) and Shortt (1923), a mistake which 

 undoubtedly has been made on more than one occasion. 



MOSQUITOES.— Hesse (1904, 1904a) found a parasite in the cells of 

 the fat body of larvse of Anopheles tnaculipennis in France. The spores 

 _ of this organism, which Hesse named Thelohania 



legeri, measured 8 by 4 microns. The filament, 

 which was extruded from the spores when placed 

 in iodine water, measured 50 microns in length. 

 The mosquito larvse seemed to be unaffected by 

 the presence of the parasite. Another species, 

 T. illinoisensis, was described by Kudo (1921) 

 from the larvse of A. punctipennis and A. qua- 

 drimaculatus of North America. It was very 

 similar to Hesse's species, T. legeri. The spores, 

 however, appeared to be smaller (4-75 to 6 

 microns), while the filament was longer (60 to 

 97 microns). In a later paper Kudo (1924) 

 describes this form in detail, and compares it 

 with T. legeri in films from A. maculipennis 

 and A. bifurcatus larvae sent to him by Hesse. 

 He comes to the conclusion that T. illinoisensis, 

 which occurs in larvse of A. crucians, as well as 

 the mosquitoes mentioned above, is identical 

 with T. legeri. It appears to be a parasite 

 specific to larvse of Anopheles, and develops in 

 the cells of the fat body. Reproduction takes 

 place by repeated binary fission. Eventually, 

 forms with four nuclei are produced (Fig. 319). 

 These divide into two sporont mother cells, each with two nuclei. The 

 two nuclei divide, and this is followed by division of the mother cell, 

 so that again stages with two nuclei are produced. The two nuclei then 

 fuse, and at the same time fine chromatin granules appear in the cyto- 

 plasm. The cell with a single nucleus is the sporont, which by successive 

 nuclear division, the first of which is mitotic, reaches an eight-nuclear stage. 

 Within it eight sporoblasts are formed, and each of these becomes a spore. 



Fig. 319. — Diagram of 

 Nuclear Changes in 

 Late Schizogony and 

 Early Sporogony of 

 Thelohania legeri. (After 

 Kudo, 1924.) 



The two nuclei in the final i^ro- 

 ducts of multiplication fuse to 

 form the nucleus of the sporont, 

 which eventually produces the 

 spores. 



