Moving through a medium as dense as water requires a significant amount of energy for a fish. This energy expenditure needs to be replenished with a greater amount of food. However, obtaining a larger quantity of food often requires movement and sometimes even migrating to other areas where sustenance is more abundant.
Remora fish have solved this problem by modifying their first dorsal fin into a perfect suction cup that allows them to attach themselves to the skin of sharks and rays, preventing them from doing anything to stop it. The suction cup is formed by transverse laminated discs located on the fish’s head and closely resemble the patterns on the sole of a boot. Since the suction disc’s surface faces backward, the suction force increases the faster the shark swims. However, a single stroke of the remora’s caudal fin, propelling the animal forward, is enough to detach it easily.
While they are young, remora fish feed on any parasites they find on the skin of their hosts, benefiting both parties. The juveniles not only find food but also a safe place to reside. In the small photo, you can see eight curious remoras peeking out from the anal opening of a whale shark, observing the underwater photographer.
However, the mouths of adult remoras are too large to consume small parasites. Most of the eight species tend to quickly leave their hosts as adults and dart toward schools of fish to obtain the necessary food. Afterward, they return to the safety and comfort provided by the sharks. Adult remoras not only provide little utility to their hosts but, on the contrary, as evident in the large photograph, the suction disc causes a massive blood effusion on the skin of the manta ray.
It is common to see several remoras attached to the hull of a shark-hunting boat after a day of slaughter, as the remoras detach from their host when the fishermen attempt to pull it out of the water and attach themselves to the first thing they find: the submerged part of the hull. The ancient Greeks were well aware of them and believed that these fish possessed the mysterious power to slow down or even stop their ships. Of course, none of this was true; the remoras simply wanted to travel without exerting much effort.
“You cannot defend what you do not love, and you cannot love what you do not know.”