THE LEUCOCYTOZOA : 



PROTOZOAL PARASITES OF THE COLOURLESS 

 CORPUSCLES OF THE BLOOD OF VERTEBRATES 



By ANNIE PORTER, B.Sc. (Lond.) 

 Zoological Research Laboratory , University College, London 



I. Introduction 



The Leucocytozoa are a group of blood parasites that are of 

 peculiar interest on account of their habitat. It is well known 

 that the chief blood elements in vertebrates are red corpuscles 

 and colourless ones called leucocytes. One function of the 

 leucocytes is that of removing from the blood various injurious 

 micro-organisms that may be present. The leucoc3>tes are 

 enabled to perform this function by means of substances 

 termed opsonins which are developed in the blood plasma. 

 The leucocytes are migratory and can become amoeboid, when, 

 by the protrusion of pseudopodia, they surround and engulf 

 protozoal and bacterial parasites and destroy the organisms 

 thus enclosed. From consideration of the above statement, one 

 would hardly imagine that the leucocytes, the destroyers of 

 intrusive organisms, would themselves be invaded by parasites. 

 Nevertheless, such is the case, and these parasites, termed 

 Leucocytozoa, both invade and live at the expense of the 

 leucocytes of the blood. 



The Leucocytozoa are microscopic, parasitic, unicellular 

 animals belonging to the same group as the malarial parasites, 

 that is, to the Hcemosporidia — minute, blood-inhabiting, spore- 

 producing organisms. The Hcemosporidia are a group of the 

 Sporozoa, a large and diverse class of parasites belonging to 

 the great phylum Protozoa, the lowest division of the animal 

 kingdom. 



II. Historical 



Many Leucocytozoa have been recorded from mammals. 

 They are known in other vertebrates, but seem to be restricted 

 at present to birds and Amphibia. Like all Sporozoa, they 

 occur more commonly in animals inhabiting the tropical zone. 



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