Yeager Documents Manta Rays and a Remora's Cloacal Entry

Researchers documented a common remora slipping into the cloacal opening of one adult Atlantic manta ray, a behavior they had not recorded before in manta rays. The study was published Monday, May 11, in the journal Ecology and Evolution.

Emily Yeager, a doctoral candidate in the Department of Marine Biology and Ecology at the University of Miami, described the behavior as "pretty weird." She said remoras are often seen riding hosts without any obvious harm, saying, "Oftentimes they're just sort of seen swimming along with their hosts with no kind of visual negative consequence to their host".

Emily Yeager and the observation

In the observation described in the study, a free diver swam near one adult Atlantic manta ray and spotted one common remora near the ray's pelvic fins. The remora quickly inserted itself into the cloacal opening after the diver's presence seemed to startle it. The manta ray briefly shuddered and then kept swimming with the remora still inside the opening.

Ecology and Evolution study

The researchers said the remora's cloacal proclivities reveal a previously undocumented behavior in one of the ocean's best known symbiotic relationships. Remoras are known for using suction discs to latch onto sharks, whales and sea turtles, and they have generally been thought to provide a cleaning service by picking parasites off the skin of the animal they ride.

University of Miami study

Yeager said the finding may change how scientists view symbiotic relationships overall. The study adds a new behavior to a relationship that has long been described in simpler terms, and it gives researchers a specific interaction to compare with future observations of manta rays and remoras.