What Are You Doing In There, Fish?

Key Points:

• Remoras use a suction cup on their foreheads to attach to larger marine animals like sharks, rays, and manta rays, traditionally thought to benefit both parties by cleaning parasites and gaining shelter and transport.
• Recent research led by Emily Yeager challenges this view, revealing remoras can harm their hosts by reducing grazing in turtles, causing physical damage with their suction, and engaging in invasive behavior such as entering the cloacae of manta rays and whale sharks.
• Yeager's 2024 study documents "cloacal diving," where remoras insert themselves into manta rays' cloacae, potentially causing harm and interfering with essential bodily functions like excretion, mating, and birthing, with no apparent benefit to the host.
• Observations suggest these remora-host relationships are more complex and sometimes parasitic rather than mutualistic, with remoras possibly using the cloaca for shelter or feeding on host feces, highlighting the nuanced and variable nature of these ecological interactions.
• The study underscores the difficulty in studying remoras due to their small size and elusive behavior, but ongoing research and technological advances may soon provide deeper insights into the full impact of remoras on their hosts.