Remoras, also called shark suckers, are a group of eight species in the mostly tropical and sub-tropical fish family Echeneidae. Remoras live primarily in the open ocean, and although they can swim on their own, they do not have a swim bladder so have trouble maneuvering long distances. Remoras can attach themselves to larger fish and marine animals and even boats using their first dorsal fin, which is modified into a characteristic flat sucking disk. Remoras are dependant on attaching to hosts in order keep water flowing across their gills, so that they get enough oxygen. Some remoras have a purely phoretic relationship with their hosts, that is, they interact with their host for the purpose of transport only, while other species will eat parasites from their host, thus providing a more mutually beneficial interaction. Most attach close to their hosts mouths and gill areas and eat the remains from their host’s meals. Some remoras will attach to many different species of fish, whales, sea turtles, rays, sharks, dugongs, and even boats. Others have much more specific host interactions, (for example the whalesucker, Remora australis, only attaches to cetaceans; the white suckerfish, Remorina albescens, rides in the mouth and gill chamber of manta rays.)
Humans have used remoras for fishing by attaching them to a line and throwing them into the sea, then pulling in the line and harvesting the fish to which the remora has attached.
Extensive information and nice pictures for the most common of the remoras, Echeneis naucrates, can be found at the Ichthyology at Florida Museum of Natural History web collections.
(Froese and Pauly 2010; Wikipedia 2012)
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