An eel-like parasite with no jaw, no bones, and a thirst for blood has been wriggling its way through the waterways of the world for thousands of years.
We’re talking about the Pacific lamprey, Entosphenus tridentatus.
This parasite is even older than trees, even, and yet has endured to the modern day.
It has some peculiar adaptations, such as a cartilaginous skeleton and a third eye with a specialized light-sensing organ.
The Pacific Lamprey are just one of around 40 different species of lamprey that arose from an ancient jawless fish ancestor during the Ordovician, and as a group they’ve survived at least four mass extinction events.