excretory system protonephridia and flame cell of sheep liver fluke fasciola hepatica on white

anatomy animal background biology cell cilia common excretory fasciola fauna flame flatworm fluke helminth hepatica illustration invertebrate isolated liver morphology nephridia nephridium osmoregulation parasite parasitic part pest physiology protonephridia protonephridium scheme science secretory sheep structure system trematoda trematode tube urinary vector white worm zoology