“Remoras’ Risky Behavior Threatens Manta Rays”

LISTEN | Full interview with scientist Emily Yeager:

As It Happens6:12Suckerfish are diving headfirst into unsuspecting manta rays’ rear-ends

Remoras, commonly known as suckerfish, have been found to exhibit inconsiderate behavior as they hitch rides by attaching themselves to larger marine creatures like sharks, whales, and manta rays. These tiny fish feed on parasites present on their hosts in exchange for transportation. However, recent research indicates that this arrangement may not be entirely beneficial for manta rays.

According to Emily Yeager, a marine researcher at the University of Miami, these fish engage in what is termed “cloacal diving” by directly entering the cloaca of the host animal, which serves as a combined reproductive and excretory opening.

The phenomenon of cloacal diving has been observed between remoras and whale sharks in the past, but a recent study, led by Yeager and published in the journal Ecology and Evolution, presents the first documented evidence of this behavior between remoras and manta rays.

While researchers have identified seven instances of this behavior occurring in various ocean regions over a 15-year period, they believe it is more common than reported. Yeager explained that the remoras wedge themselves deeply into the cloaca, possibly as a response to fear.

Brooke Flammang, a professor at the New Jersey Institute of Technology who has studied remoras, suggested that the behavior might be driven by the remoras seeking food, a phenomenon known as coprophagy, or consuming feces.

Despite the unusual nature of this behavior, Flammang emphasized that remoras are known for their peculiar habits and territorial tendencies. She noted that the fish’s actions, including cloacal diving, are not entirely surprising.

Impact on Manta Rays

Yeager expressed concerns about the potential harm caused to manta rays by cloacal diving. She mentioned documented instances of skin damage in other host species due to remoras’ suction cup attachment and highlighted the sensitivity of the cloaca, which could lead to severe damage affecting reproduction and waste excretion.

If cloacal diving proves detrimental to manta rays, Yeager pointed out that it challenges the conventional classification of the relationship between the two species as either symbiotic or commensal. She suggested that such interactions likely exist on a spectrum rather than in clear-cut categories.