366 Animal Biology 



species which happen to carry the sporozoite (spore) stage of the malarial 

 parasite. The female mosquito of the genus Anopheles (an -of el ez) 

 (Gr. anopeles, hurtful) transmits malaria, while the ordinary mosquito 

 of the genus Culex (ku'leks) (L. culex, gnat) does not (Figs. 176, 202, 

 and 303). 



Motion and Locomotion. — In the adult stages Plasmodium, does not 

 possess locomotor organelles, although certain immature stages may be 

 motile. These will be noted later in the discussion of reproduction. 



Ingestion and Digestion. — Sporozoa have no digestive organelles but 

 they absorb foods from their surroundings. Since they are parasitic, they 

 undoubtedly enjoy many "precooked" meals at the expense of the hosts. 



Circulation. — The Sporozoa are so small that they do not require 

 circulatory equipments but can rely upon the flowing of protoplasm 

 (cyclosis) within their cells. 



Respiration. — The limited oxygen requirements are probably sup- 

 plied by taking it in through the general body surface. 



Excretion. — The parasitic sporozoa, taking in foods from their hosts, 

 probably do not need to excrete great quantities of wastes and do so 

 through the general body surface. 



Coordination and Sensory Equipment. — The parasitic habits probably 

 explain the absence of specific sensory equipments. 



Reproduction. — The spindle-shaped spores, called sporozoites (spo ro- 

 zo'ites) (Gr. sporos, spore; zoon, animal) (Fig. 176), in the saliva of 

 a diseased female mosquito are thrust into the human wound by the bit- 

 ing mouth parts and enter the human red blood corpuscles where they 

 become amoeba-like trophozoites (trof o -zo' ite) (Gr. trophe, nutrition; 

 zoon, animal) which feed at the expense of the red blood corpuscles. In 

 about fifty hours the trophozoite becomes a schizont (shiz' ont) (Gr. 

 schizein, divide), which divides (sporulates) to form from fifteen to 

 twenty-four merozoites (me ro -zo' ite) (Gr. meros, part; zoon, animal). 

 The merozoites are liberated into the blood stream in about eight hours 

 and attack other red blood corpuscles. The time of liberation of mero- 

 zoites parallels the attack of fevers and chills. Some merozoites develop 

 into additional schizonts again, while other merozoites became sex cells, 

 called gametocytes (gam' et o site) (Gr. gamos, spouse; kytos, cell). 

 These m.ale and female gametocytes may be picked up by the biting 

 female mosquito from the blood stream of a malarial patient. The 

 female gametocyte forms a macrogamete (egg). The male gametocyte 

 forms from six to eight elongated microgametes (sperm). A sperm and 

 egg fuse to form a zygote which changes into a motile, wormlike ookinete 



