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. The behavior, called “cloacal diving,” further hints that the relationship between the two types of animal is more complicated than previously thought.…