The Ocean's Most Awkward Relationship
If you thought your commute was uncomfortable, spare a thought for the manta ray.
New research — picked up by CBC's As It Happens — has revealed that remora fish, commonly known as suckerfish, aren't just hitching a ride on their manta ray hosts. They're apparently diving headfirst into the rays' cloaca: the all-purpose rear opening that manta rays use for reproduction, waste, and, apparently, uninvited guests.
It sounds like a punchline. Scientists confirm it is, in fact, just biology.
What Is a Suckerfish, Exactly?
Remora are slender, torpedo-shaped fish that have evolved a modified dorsal fin into a flat, ridged suction disc on top of their heads. They use this disc to latch onto larger marine animals — sharks, rays, whales, sea turtles — and get a free ride through the ocean while feeding on scraps, parasites, and whatever else their host stirs up.
It's a relationship scientists call commensalism: one party benefits, the other is largely unaffected. Or so we thought.
The, Uh, Findings
Researchers observing manta rays in the wild documented remora repeatedly orienting themselves toward the rays' cloacal openings and, in some cases, inserting themselves partially inside.
The behaviour appears deliberate. Remora seem to be attracted to the warmth, shelter, and nutrient-rich environment near the cloaca — possibly feeding on mucus or microorganisms found there. For the manta ray, scientists say the intrusion is likely irritating but not seriously harmful.
Manta rays observed during the study were frequently seen shaking, rolling, and performing sudden directional changes — behaviours that researchers now believe may be attempts to dislodge their overly intimate passengers.
In short: the manta rays are not thrilled.
Why This Matters Beyond the Obvious Jokes
Quirky as the headline is, the research contributes to a growing body of work on cleaning station ecology — the complex social and biological interactions that happen when large marine animals congregate at specific reef sites to have parasites removed by smaller fish.
Understanding what remora actually do — and what they eat — helps scientists build a clearer picture of reef ecosystem dynamics, nutrient cycling, and host-parasite co-evolution.
It also raises questions about where the line falls between commensalism and parasitism. If a suckerfish is causing a manta ray genuine distress and competing for bodily resources, the relationship may be more exploitative than previously assumed.
The Bigger Picture
Manta rays are listed as vulnerable to extinction globally, with populations threatened by bycatch, targeted fishing for gill plates, and habitat degradation. Research that deepens our understanding of their behaviour and ecology — even the embarrassing parts — ultimately supports conservation efforts.
So yes, the story involves fish in a ray's backside. But it's also a reminder that the ocean is stranger, more intricate, and more alive than we tend to imagine from the surface.
Nature, as always, contains multitudes.
Source: CBC Radio / As It Happens
