Source: Grist

Excerpt:

When Chelsea Wood was a child, she would often collect Periwinkle snails on the shores of Long Island. 

“I used to pluck them off the rocks and put them in buckets and keep them as pets and then re-release them,” Wood said. “And I knew that species really well.”

It wasn’t until years later that Wood learned that those snails were teeming with parasites. 

“In some populations, 100 percent of them are infected, and 50 percent of their biomass is parasite,” Wood said. “So the snails that I had in my bucket as a child were not really snails. They were basically trematode [parasites] that had commandeered snail bodies for their own ends. And that blew my mind.”

Read more: Nature can’t run without parasites. What happens when they start to disappear?