A new study documents remoras diving into manta rays’ cloacas, raising questions about whether the hitchhiking fish are hiding, feeding or harming their hosts.
Remoras, the suckerfish best known for hitching rides on larger marine animals, have now been documented diving headfirst into manta rays’ cloacas, a behavior researchers say may be more common than previously recognized.
The behavior, described as “cloacal diving,” involves the fish pushing into the manta ray’s cloaca, the opening used for reproduction and waste. Emily Yeager, a University of Miami marine researcher and PhD candidate, led a study on the phenomenon published this month in the journal Ecology and Evolution.
Researchers recorded seven instances in different parts of the ocean over a 15-year span. The number is small, but Yeager told CBC Radio’s As It Happens that the behavior may be overlooked because observers often see only “the very tip of the tail poking out from the backside of the manta ray.”
Remoras usually attach to animals such as sharks, whales and manta rays, gaining transportation while feeding on parasites. That relationship is often treated as beneficial or at least harmless to the host. The newly documented behavior suggests the arrangement may be more complicated for manta rays.
What motivates the fish is not settled. Yeager suspects the dives may sometimes be a fear response. In one video described in the CBC report, a diver approaches a male Atlantic manta ray off Florida, apparently startling a nearby remora. The fish then dives into the ray’s cloacal opening, after which the manta ray shudders before swimming on.
Brooke Flammang, a New Jersey Institute of Technology biology professor who studies remoras and was not involved in the study, offered a different explanation: the fish may be feeding. In an email cited by CBC, Flammang said the behavior is likely coprophagy — eating feces — and noted that remoras can be territorial when sharing a host.
The effect on manta rays is also uncertain. Yeager said it is impossible to know how the ray experiences the intrusion, but she noted that remoras have been documented causing skin damage to other host species with their suction cups. If similar damage occurred inside the cloaca, she said, it could affect sensitive functions such as reproduction and waste excretion over time.
For now, the finding appears to complicate a familiar marine relationship rather than settle it. Scientists have long described remora-host interactions as symbiotic or commensal, depending on whether the host benefits or is simply unaffected. Yeager said the behavior suggests those relationships may exist on more of a spectrum.
نظرات (0)