It was tested for its ability to adhere to the inside of the digestive tract.
Remora adhesive disks are an evolutionary adaptation of the fish’s first dorsal fin, the one that in other species sits on top of the body, just behind the head and gill covers. The disk rests on an intercalary backbone—a bone structure that most likely evolved from parts of the spine. This bony structure supports lamellae, specialized bony plates with tiny backward-facing spikes called spinules. The entire disk is covered with soft tissue compartments that are open at the top. “This makes the remora fish adhere very securely to soft-bodied, fast-moving marine hosts,” Traverso says.
A remora attaches to the host by pressing itself against the skin, which pushes the water out of these compartments, creating a low-pressure zone. Then, the spinules mechanically interlock with the host’s surface, making the whole thing work a bit like a combination of a suction cup and Velcro. When the fish wants to detach from a host, it lifts the disk, letting water back into the compartments to remove the suction. Once released, it can simply swim away.