"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

June 5, 2010

June 5 - Macracanthorhynchus hirudinaceus

Today's parasite has quite a handle of a Latin name - perhaps you'll prefer the common name - "Giant Thorny-Headed Worm of Swine." As that moniker suggests, this is an acanthocephalan, and like its relatives has a life cycle that alternates between an invertebrate and a vertebrate. The eggs of this parasites are eaten by beetles where they will develop into juveniles or cytacanths. These insects then get eaten by pigs (or occasionally dogs or even humans in very rare cases). The adults attach themselves to the small intestinal wall and can get quite large - up to 65 centimeters. The eggs pass out with the pig's feces and interestingly, if a bird accidentally eats them if they are on something that they're gobbling up, they pass right through unharmed to wait for the right (beetle) host.

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