Scientists suspect that the behavior could harm the manta rays, suggesting a complex relationship between remoras and their hosts that can sometimes be parasitic

Remoras might dive into manta rays' rear ends when they're scared. Bryant Turffs / Marine Megafauna Foundation

Remoras are often called “suckerfish” because of the suction cup-like organ atop their heads. It allows them to stick onto marine animals like whales, rays and dolphins so they can travel as hitchhikers . But it turns out that these clingy fish aren’t just attaching themselves to their hosts’ exteriors.

Sometimes they take a deep dive where the sun doesn’t shine.

In a study published May 11 in the journal Ecology and Evolution , researchers describe several instances of remoras burrowing deep inside manta rays’ backsides.…