I got to look inside a lot of alligators a couple of weeks ago. One thing that surprised me was that there were no obvious parasites sitting in either their muscles or their guts. This is, believe me, not true of mammals.
So I got curious – where were the parasites in these animals? I asked around, and no one at the Rockefeller Wildlife Refuge had ever seen parasites inside alligator muscle or intestines, or more than a few big roundworms in their stomachs. But their lungs were another story entirely. Their lungs are full of tongue worms.
Tongue worms belong to a phylum of animals called pentastomids . They’re all parasites, and their adult forms are only found in the respiratory tracts of carnivorous reptiles, birds, and mammals. They look a bit like segmented worms, but there are a few significant differences. For one, they’re covered in a hard cuticle that they have to shed when they grow, which suggests they’re much more closely related to arthropods than to earthworms. They also have five stubby lobes on their heads. The central lobe contains the tongue worm’s mouth, but each of other four bears a sharp hook to ram into its host’s lung tissue.