In a bizarre twist of marine behavior, remoras have been spotted taking a dive into the rear ends of manta rays, leaving researchers both puzzled and intrigued. This peculiar phenomenon, known as “cloacal diving,” has raised questions about whether these clingy fish are seeking food, shelter, or something else entirely.
Emily Yeager, a marine researcher from the University of Miami, shared her astonishment during an interview on the Canadian Broadcasting Corporation’s show “As It Happens.” “These fish are heading right into some manta ray rear-ends,” she remarked, highlighting the unusual nature of this behavior.
Cloacal diving involves remoras slipping in and out of the cloaca, a multi-functional orifice used for excretion and reproduction. While remoras are typically seen as harmless hitchhikers, cleaning parasites off larger marine animals like sharks and whales, this new behavior suggests a more complex relationship.
Previously, researchers had observed remoras engaging in similar antics with whale sharks, but this marks the first documented instance of them infiltrating manta rays. Brooke Flammang, a biology professor at the New Jersey Institute of Technology, noted, “Remoras are just that weird,” emphasizing the strange nature of their behavior.
Over a 15-year period, researchers recorded seven instances of this cloacal diving across various ocean locations. Yeager suspects that the frequency of these events is underreported, as the remoras often leave only the tip of their tails visible when they dive in.
The reasons behind this unusual behavior remain unclear. In one recorded instance, a startled remora was seen disappearing into a manta ray’s cloaca, prompting the ray to close its opening and swim away with the fish still inside. This has led some scientists to speculate that the remoras might be engaging in coprophagy, or eating feces, potentially competing for prime feeding spots.
Flammang described how remoras can be territorial, suggesting that their foraging habits might lead them to explore less conventional areas. “They can be territorial about sharing space on the same host,” she explained, hinting at the competitive nature of these fish.
While it’s difficult to ascertain how manta rays feel about this probing behavior, Yeager theorizes that it may not be welcomed. She warns that such interactions could have negative implications for the manta rays over time, potentially affecting their reproductive and waste-excretion functions.
As Yeager put it, the relationship between remoras and manta rays might not be as mutual as once thought, existing instead on a spectrum much like any relationship in life. What other secrets might the ocean hold about these curious creatures?
