It’s easy to ignore a remora, the little torpedo of a fish that hitchhikes on sharks, whales, and turtles. But this diminutive creature is full of secrets, not least of which may be the inspiration for versatile adhesive technology of the future.
Often called suckerfish, remoras are content to make an inglorious living on the scraps, parasites, and feces of larger creatures. In addition to food, the remora also gains easy transportation and protection through this relationship—after all, who’s going to mess with the guy attached to the tiger shark?
Unlike a leech, which hitches a ride with its mouth, the remora uses a non-invasive suction pad on its forehead. (The remora’s relationship to the host is not considered parasitism, but commensalism.) This pad, which is actually an adapted dorsal fin, consists of overlapping ridges called lamellae. By flexing and relaxing these ridges like venetian blinds, the remora creates just enough suction to hang on while leaving its little jaws free for feasting. Best of all, the attachment seems to be passive, meaning the remora need not waste much energy to ride along.
These are just a few of the findings from a new materials research project out of Georgia Tech. One of the paper’s lead researchers, Jason Nadler, explains, “If I was evolving to, say, hang from a bar by my hands, it wouldn’t make a lot of sense to constantly waste energy holding myself up. The remora’s suction is its natural state. It’s probably using more energy to detach than anything else.”
To learn more about remora adhesion, Nadler and his fellow authors at Georgia Tech busted out sorcery such as microtomography, optical microscopy, and scanning electron microscopes to study the fish’s lamellae. Notably, the team revealed microscopic spinules or spines on the end of each lamella. These studs are probably why a remora’s suction pad is smooth when brushed one way and sandpaper-y the other.
“Spinules increase friction between the remora and its host,” says physics research scientist Allison Mercer, the paper’s other lead author. “But we’re still learning exactly how the anatomies match up.”
The spacing of spinules seems remarkably similar to the spacing of a mako shark’s dermal denticles, which are the scales that make up shark skin. Still, scientists don’t like to get too willy-nilly with correlations, so Mercer stressed that further study will be crucial to understanding just how these spinules interact with their environment and how we can best harness their efficiency. For instance, spinules and lamellae may play different roles for different surfaces, explaining why remoras can quickly attach (and detach) to both smooth and rough surfaces.
Nadler, who is a material research scientist, is optimistic about the implications of such research. His goal is to take what the remora has gained from evolution and improve upon it for more versatile applications than shark-riding. “Simply creating a rubber remora is the wrong way to go about it,” he says. “I think we need to look more closely at the features and what the spinules are actually doing, then replicate that function.”
More research is afoot, as is speculation toward potential applications. Possible uses include everything from surgical tools, wound closures, and painless bandages to military reconnaissance, robot climbing feet, and marine conservation. In fact, Mercer explained that the idea to study adhesion in remoras originally came from a whale shark scientist wishing for a better way to attach tracking devices. (In case you’re wondering, this is why you’d want to track a whale shark.)
Interestingly, this is not the first time humans have looked to remoras for help. Various sea-faring peoples have learned that if you tie a rope to a remora’s tail and toss it into the water above a sea turtle, the fish will swim straight to the turtle and lock on, enabling you to haul both of them up.
So if the whole futuristic surgical suture thing doesn’t work out, at least we’ll always know how to reel in sea turtles—though, on second thought, this party trick probably won’t win you many friends.