144 



THE AMOEBAE 



ENTAMOEBA MURIS 

 (GRASSI, 1879) 



Synonyms : Amoeba miiris. Council- 

 mania muris, Councilmania decumani. 



E. muris occurs commonly in the 

 cecum and colon of rats, mice and the 

 golden hamster thruout the world. An- 

 drews and White (1936) found it in 10.4% of 

 2515 wild rats in Baltimore. Fry and Mel- 

 eney (1932) found it in 48% of 48 wild Rattus 

 norvegicus and 24. 1% of 54 grey mice cap- 

 tured in a rural area of Tennessee. Tsuchiya 

 and Rector (1936) found it in 8% of 100 rats 

 in St. Louis. Elton, Ford and Baker (1931) 

 reported it in 50% of 440 long-tailed field 

 mice (Apodemus sylvaticus), 4l"/o oi 116 bank 

 voles {Clelhrionomys glareolus) and 41% 

 of 51 short-tailed field mice {Microtus 

 hirtus) in England. Wantland (1955) found 

 it in 33% of 412 golden hamsters from sev- 

 eral American suppliers and laboratories. 

 Mudrow-Reichenow (1956) found E. luuris 

 in 7% of 14 golden hamsters, 35% of 21 

 laboratory rats and 39% of 92 laboratory 

 mice in Germany. 



Kessel (1924) transmitted E. muris 

 from the rat to the mouse and vice versa. 

 Neal (1947, 1950a) and Saxe (1954) infected 

 rats with E. uiuris from the golden ham- 

 ster and mouse. Saxe (1954) infected the 

 golden hamster with E. muris from the rat. 



E. muris is morphologically similar 

 to E. coli. Its trophozoites are 8 to 30 /i 

 long. Its cysts are 9 to 20jj, in diameter 

 and have 8 nuclei when mature. Its nu- 

 clear structure and division were studied 

 by Wenrich (1940). He found that the nu- 

 cleus is intermediate in structure between 

 those of E. kislolylica and E. culi but 

 more nearly resembles the latter. It var- 

 ies in diameter from 3 to 9fi with a mean 

 of 4 to 5 |i. In division, approximately 8 

 chromosomes are formed. Binucleate 

 cysts almost always contain a large gly- 

 cogen vacuole, and mononucleate cysts 

 very frequently do. 



E. muris is non- pathogenic. It is 

 important to the research worker because 

 it must be differentiated from other amoe- 

 bae introduced in experimental infections. 



ENTAMOEBA CAVIAE 

 CHATTON, 1918 



This species is often referred to as 



Entamoeba cobayae (Walker , 1908) Chatton, 

 1917. However, the form which Walker 

 (1908) called Amoeba cobayae -wcls seen in 

 cultures from a guinea pig intestine and 

 was not an Enta»ioeba at all. Hoare (1959) 

 considered this species a synonym of E. 

 muris. 



E. caviae is common in the ceca of 

 laboratory guinea pigs. Nie (1950) found 

 it in 14% of 84 guinea pigs in Pennsylvania 

 and Mudrow-Reichenow (1956) found it in 

 46% of 13 guinea pigs in Germany. 



E. caviae resembles E. culi. Its 

 morphology has been studied by Nie (1950). 

 The trophozoites are 10 to 20 )i in diam- 

 eter with a mean of 14.4jj,. The nucleus 

 is 3 to 5 (i in diameter. Its endosome var- 

 ies in size and shape and may be central 

 or eccentric. In some cases it is com- 

 posed of several granules. There is a 

 ring of coarse chromatin granules inside 

 the nuclear membrane. The cysts are 11 

 to 17 |i in diameter with a mean of 14^ 

 and have 8 nuclei (Holmes, 1923). They 

 are rare. 



E. caviae is non- pathogenic. Because 

 it is so common, it must be differentiated 

 from other amoebae in experimentally in- 

 fected animals. 



ENTAMOEBA CUNICULI 

 BRUG, 1918 



This species occurs in the cecum and 

 colon of the domestic rabbit. It is not 

 pathogenic. It resembles^, coli, and 

 Kheisin (1938) has even suggested the name 

 Entamoeba coli forma cnniculi for it. 

 Hoare (1959) considered it a synonym of 

 E. muris. It is apparently quite common 

 in rabbits, altho there seem to be relatively 

 few reports on it. Kheisin (1938) found it 

 in 25% of the rabbits he examined in Russia. 

 The trophozoites range from 12 to 30 ji in 

 length with means of 13 to 17 fi in different 

 rabbits. The cysts have 8 nuclei. They 



