HERON BECOMES INFECTED BY EATING FISH 

 WORM BECOMES ADULT IN MOTTTH CAVITT 



EGG PASSES OUT IN FECES OR SALIVA 



BODY OF CERCARIA 

 PENETRATES FISH, 

 BECOMES YELLOW 

 GRtJB 



MIRACIDIDM PENETRATES 

 HELISOMA SNAIL 



MOTHER SPOROCTST 



- - LARVAL STAGES IH SNAIL 



CERCARIA EMERCES FROM SNAIL 

 Figure 5.--Life cycle of the "yellow grub," Clinostomum marginatum. Outer circle (solid line) includes the worm stages. Inner circle 



(broken line) includes the hosts. 



is usually found in greater numbers on the 

 body than on the gills; most of the others 

 occur on the gills only. 



5. Parasitic copepods. In some ponds and 

 hatcheries, the "anchor worm" copepod 

 CLemoeoj flourishes. It protrudes wormlike 

 from the fish, usually at the base of a fin, 

 with its head buried in the fish. The visible 

 portion is cylindrical, whitish, and about 

 1/2 inch long (fig. 8). There are often two 

 egg sacs extending from the end of the 

 creature. With care, the head can be dis- 

 sected out of the fish, and one can then see 

 that some of the forward appendages have 



become modified into a very efficient "an- 

 chor." This parasite goes through several 

 microscopic developmental stages usually 

 on the gills of fish other than the one on 

 which it finally matures. Because it can do 

 considerable damage to fish if present in 

 large numbers, it should be eradicated from 

 fish rearing ponds and hatcheries, and 

 parasitized fish should not be used for 

 stocking. 



Sometimes "fish lice" (Argulus) may be 

 seen crawling over a fish. They are among 

 the largest of external parasites and can be 

 seen easily. They are round to oval when 



