In a river of northern Brazil, an “armored” creature swam through the water in search of its next meal — or tried to at least. But something caught the striped animal and pulled it to the surface.

Looking at the fish in a laboratory, researchers quickly realized they’d discovered a new species: Hypancistrus seideli, or Seidel’s armored catfish. Several Hypancistrus seideli, or Seidel ...

Armored catfish are driving manatees out of their warm-water refuges, putting their health at risk. Here’s why it’s happening—and what scientists are doing to help. An invasive armored ...