Remora is the name given to a variety of fish species of the family Echeneidae (which contains the genera Echeneis, Phtheirichthys, Remora, and Remorina). The unifying characteristic of these fish is their dorsal fins which occur as flat, oval-shaped discs and enable the fish to attach themselves to larger organisms. Remoras use their ability to cling to larger creatures for protection, free travel, and free food. With the exception of some dolphins, whose skin can be eaten away by remoras that cling in place too long, remoras don't harm their hosts, sometimes even benefitting their hosts by feeding on parasites that attach themselves to the host's body. Remoras have also been called sucker fish.
The fish's name comes from the Latin word remorari, meaning to linger or delay. In ancient times, the fish were thought to slow down or even outright halt ships by attaching to the craft. The ancient Greeks called remoras 'ship-stoppers.' Legend has it that remoras delayed both Roman Emperor Caligula and Marcus Antonius during crucial battles. Remoras have been ground up and used in potions with the purpose of delaying childbirth or extending sex. The idea behind these purposes in potions is thought to have come from their legendary ability to slow or stop ships: If the fish could slow down a massive boat, surely they could be used to slow development of a fetus or prevent premature ejaculation. In Madagascar, dried remoras were placed around the necks of unfaithful spouses in order to get them to return and stick with their husbands or wives. In reality, remoras are nowhere near that powerful. Remoras' suction power is enough to enable some natives in tropical regions to use them to catch sea turtles and other fish. The fishing line is attached to the end of a remora's tail and the fish is let loose. When the remora attaches itself to a turtle or larger fish, the fisher can reel in the remora complete with its host.
Remoras can be found in warm waters throughout the world, primarily in tropical regions (though some can be found as far north as the waters off Long Island). The common remora (Remora remora) is likely the most famous for its seemingly dangerous habit of attaching itself to sharks, most noteably the Great White. While a remora can be an occasional meal for a shark, the fish are actually safer clinging to sharks and other creatures than swimming freely. After all, how many predators are willing to risk being eaten by a shark to eat a small fish? Remoras can swim freely but most prefer being attached to some larger creature such as a shark, sea turtle, large type of fish, dolphin, manta ray, porpoise, or whale. Larger hosts may have as many as three remoras hanging on around their mouths. Different species of remora prefer different hosts. Occasionally remoras have been spotted clinging to ships or even human divers mistaken by the fish for larger sea creatures.
Once attached to a host, some remoras may briefly detach of their own free will to eat scraps of the host's food or parasites thrown off the host that are out of reach of the remora while it is still hanging on its host. In water-filled caves in the Yucatan, where sharks can occasionally be found bathing in freshwater currents, remoras have been seen detaching themselves from their hosts to feed on parasites now-removed from their host shark's body. A lagoon in Bimini Island is home to the spectacle of not only lemon sharks giving birth but remoras darting into the midst of it all to eat the afterbirth. The relationship between a remora and its host is an example of commensalism; one member of the symbiotic relationship gaining greatly from it and the other gaining either little or nothing.
Despite remoras' desire to cling to a larger organism, the fish are excellent swimmers on their own and some (usually juveniles) can be found living in shallow waters and coral reefs, feeding on small crustaceans. Remoras have been seen to swim in circles without a host, waiting for a larger creature to come along. Remoras have even been seen attached to each other in a stack, with the smallest on bottom and the largest on top, while circling.
Remoras most often attach themselves to their hosts near the mouth area or at least somewhere the fish can easily feed on scraps of food missed by the larger creature. Some remoras, however, have been observed venturing completely inside their hosts' jaws or within the hosts' gill chambers, devouring any parasites found within. In this case, the remoras do more than just hang on for a free ride and food but are actually beneficial to the health of their hosts.
A hopefully complete at-the-time-of-this-writing list of known remora species:
- Echeneis naucrates (aka live sharksucker) - The most abundant species of remora, E. naucrates can be found swimming without a host in shallow waters and reefs and isn't particularly picky about its host species. E. naucrates will attach itself to dolphins, large and bony fish (such as swordfish), rays, sea turtles, sharks, and whales and have been known to occasionally attach to ships. The live sharksucker has also been known to follow divers around. E. naucrates can grow to be 110cm in length, making it the largest species of remora.
- Echeneis neucratoides (aka whitefin sharksucker) - Found in slightly cooler subtropical regions than most of its brethern, E. neucratoides can be found along the Atlantic coast of the United States and in the Gulf of Mexico. E. neucratoides can grow to be 75cm in length.
- Phtheirichthys lineatus (aka slender suckerfish) - The long and slender P. lineatus is willing to attach itself to a variety of fish and sea turtles but its most preferred host is the barracuda. Aside from attaching to its host's body, P. lineatus will also venture inside its host's gill chambers and eat parasites found within. P. lineatus can grow to 76cm in length.
- Remora australis (aka whalesucker) - The whalesucker, as the name implies, will attach itself to whales and porpoises. Unlike other species of remora, the whalesucker will only attach to these animals. Remora australis can grow to be 76cm in length and is found primarily in oceanic waters.
- Remora brachyptera (aka spearfish remora) - As the common name implies, the spearfish remora will attach itself to spearfish, as well as billfish and swordfish. Not as picky about its host as the whalesucker, Remora brachyptera can occasionally be found clinging to other types of fish as well. As with P. lineatus, the spearfish remora will venture into its hosts gill chambers in search of food. Remora brachyptera can grow to be 40cm in length.
- Remora osteochir (aka marlin sucker) - As the common name implies (once again), the marlin sucker prefers the marlin as its host, as well as sailfish and, on occasion, other larger types of fish. Similar to Remora brachyptera, Remora osteochir can be found on the body or within the gill chambers of its host and can reach up to 40cm in length.
- Remora remora (aka common remora, shark remora, sharksucker) - Probably the most well-known, the common remora prefers attaching itself to sharks but will also cling to sea turtles and ships it mistakes for large fish. Common remoras can sometimes be found swimming freely, not attached to any other creatures. The younger common remoras spend more time feeding off parasites than stray particles of food. Remora remora can grow to be 86.4cm in length.
- Remorina albescenes (aka white suckerfish) - The white suckerfish's preferred host is the manta ray, though the species will also attach itself to sharks and black marlin (Makaira indica). White suckerfish are very rarely found swimming free and are one of the remora species that can be found in their hosts' gill chambers. In addition to this, a white suckerfish will even venture into its host's mouth. Remorina albescenes can grow to be up to 30cm in length.