PARASITISM 



175 



An example of another trematode life cycle is shown in Fig. 86. In 

 this case the adult fluke lives only in the lung of a frog and during the 

 course of the life cycle two different intermediate hosts are required. 



1 Jn?; fr!:^T^^ ''J^ ^'l*u''^ °^ ^ ^T^ trematode, Haematoloechus medioplexus, of the frog. 

 1. adult trematode from the lung of the frog, Rana pipiens. {From W. W Cort 1915 ) I 

 egg contaming miracidium. Passes from frog in feces; does not hatch until ;aten by 3 

 Planorhula armigera, a snail. The eggs hatch in this snail and sporocysts develop in the 

 liver. 4, sporocyst containing developing cercaria. 5 mature cercaha. It leaves the 

 snail, swims about in the water, enters the branchial basket of dragonfly nymphs. 6, 

 ZTJ'^A ^^^ ""^J' '^'''^"f encysted in nymph. 8, mature dragonfly containing 

 encysted cercana When eaten by a frog, the trematode larvae emerge and pass up thS 



ri^?^-'/?"'" '^p'r^.- ^""'n'"^ "■ ^- ^''^"'^'•' ''^Laboratory Manual ir. Animal Para- 

 sitology, Burgess Publishing Company. Figure 7 from Krull, 1930.) 



