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The remora could be described as the deadbeat freeloader of the fish world. Or perhaps the world's greatest hitchhiker.
Also called a sharksucker or whalesucker, the remora has evolved a sucker-like organ on its back that allows it to attach itself to other fish. Once attached, the remora gets a free ride around the world.
The remora belongs to a class of fish called the spiny ray fish, according to Tracey Sutton, assistant professor of marine science at the Virginia Institute of Marine Science.
Spiny ray fish — which include grouper and snapper — have two dorsal fins. Their first dorsal fin is a line of spines that the fish puts up when it’s being attacked. The erect spines make it difficult for a predatory fish to swallow the fish. Spiny ray fish have a second dorsal fin comprised of soft rays that they use to steer, says Sutton. There are eight species of remora.
The remora’s sucker pad is actually a modified dorsal fin, according to Sutton. It’s believed that the remora used to have spines growing from its first dorsal fin, but somewhere along its evolution it lost the spines but retained the muscles that used to support them, and it’s these muscles that form the sucker pad.
The sucker organ has folds that look similar to Venetian blinds that open and close to create suction. This allows the fish to gain a firm hold against the skin of its host. The remora can increase its suctiony grip by sliding backward on the fish it’s attached to; and it can decrease its hold, and release itself, by sliding forward.
Remoras can swim well on their own but they prefer to attach themselves to other fish. Since the remora’s sucker is on its back, it usually attaches itself to the underside of the host fish. It doesn’t draw blood or other nutrients from its host, like a leech.
The remora attaches itself to its host fish and after that, only has to hold on and let the host fish do all the work.
It's lower jaw projects out farther than its upper, and it's believed that the remora lowers its bottom jaw and scoops up food as the host fish swims along. It will also eat scraps of food dropped by its host. It will disattach itself long enough to scavenge food scraps, then reattach itself to the host fish or to another fish.
The remora is also called a sharksucker or whalesucker because it is most commonly found attached to sharks and whales. But the remora will attach itself to any marine animal large enough to carry it, including manta rays, sea turtles and even scuba divers. (Note to snorkelers and scuba divers: If a remora ever attaches itself to you, you can remove it by sliding it forward. This releases the suction).
By being attached to the belly of a shark or whale, the fish also gains protection. It’s a relationship known as commensalism. The remora gains food, protection and transportation, and while the host fish gains nothing from the relationship, it also loses little.
The remora is native to tropical waters but has been found in oceans all over the world, including temperate and arctic waters, after having hitchhiked there on the bellies of host fish or the hulls of ships.
Some cultures have used remoras to catch sharks and turtles, according to Sutton. They attach a cord to the remora’s tail and release it when they sight a shark or turtle. The wily fish usually heads directly for the prey and fastens itself to the turtle's shell. The fishermen then pull in the remora, with the shark or turtle attached.
Remoras will also attach themselves to the hulls of ships. If enough remoras fasten themselves to the bottom of your ship, the added drag can greatly slow down the ship’s forward progress.
The remora, in fact, derived its name from the practice of attaching itself to the hulls of ships. In Latin, remora means “delay.” Sailors considered it bad luck to have a remora attached to their ship. Pliny the Younger, in his book "Natural History," blames the defeat of Mark Antony at the Battle of Actium (a naval engagement fought between the forces of Octavian and the combined forces of Mark Antony and Cleopatra VII) on the remoras that had attached themselves to Mark Antony’s ships.
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