You know all those pictures of big, powerful sharks or graceful manta rays? Have you ever noticed the tiny little fish that are usually present on the shark or ray? Have you ever taken the time to ask yourself ‘What is that?’? I never have. Until today.

Common remoras are part of the suckerfish family, which are all known for attaching to marine animals. Common remoras are found all around the warmer parts of the oceans, including the Mediterranean and North Sea.

I think remoras look like they are swimming upside down.
Image by NOAA CCMA Biogeography Team, Public domain, via Wikimedia Commons

These fish can grow to be almost a metre long, but are more commonly seen around lengths of 40 cm. The most notable feature of remoras is the suction disc on its head, which is a modified dorsal fin. This allows remoras to attach themselves to larger animals for a free ride-a-long. Another weird trait of remoras is their mouths, which basically look like they are upside down, giving remoras a very strange facial expression.

Common remoras have been found attached to sharks, sea turtles, whales, and dolphins. Remoras don’t have any negative effects on their hosts, and it is thought that each party benefits from the other. Remoras get a significant portion of their food from their host, as they eat parasites off of their hosts’ bodies, as well as ingesting any scraps from the hosts’ meals. In return, the hosts get cleaned of parasites by the remoras. The remoras also get a free ride, which is not only fun, but useful, since remoras require moving water flowing over their gills to breathe.

The remora’s sucker organ. Pretty gross, right?
Image by Mohammad Moazzam Khan, CC BY 3.0, via Wikimedia Commons

I have to say, I think remoras are pretty ballsy fish. It takes a lot of guts to be a small little fish and spend your life attaching yourself to creatures that are much, much bigger than you. Especially when some of those creatures are cold-blooded killers. Still, remoras manage to find a way to make it work, and their hosts don’t seem to mind too much: remora remains have never been found inside a shark’s stomach. Where they have been found is inside a sharks mouth, with small remoras cling to get tasty food particles. That definitely takes nerves of steel.

While remoras themselves are not used for human consumption, some savvy fishermen have found a way to exploit remoras’ sucker discs. They will catch a remora and tie a line to the fish’s tail, and then release it. The remora will then go an find a nice big sea creature to attach itself to, thereby leading the fisherman right to it.

For little fish that spend most of their lives attached to other, seemingly more interesting animals, remoras actually have quite a lot going on. They do look super weird though.