Animals or organisms that live inside other animals as parasites, like tapeworms or roundworms living in intestines.
From endo- (within) + zoa (plural of zoon, from Greek zōon meaning animal). This scientific term literally means 'animals within.'
Endozoa were absolutely terrifying to ancient and medieval people who didn't understand germ theory—discovering that you could have whole creatures living inside you was like finding aliens in your own body!
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