The common remora (''Remora remora'') is a

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

marine fish belonging to family Echeneidae. The dorsal fin, which has 22 to 26 soft rays, acts as a

suction cup A suction cup, also known as a sucker, is a device or object that uses the negative fluid pressure of air or water to adhere to nonporous surfaces, creating a partial vacuum. Suction cups are peripheral traits of some animals such as octop ...

, creating a

vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...

to allow it to attach to larger marine animals, such as whales, dolphins, sharks, and sea turtles.

Physical characteristics

The common remora has a suckerlike dorsal fin and an anal fin. Its body can be brown, black or grey in color. It can reach in

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

, though most do not exceed . The maximum known weight of this species is .

Biology and behavior

''R. remora'' and its host seem to partake in a

symbiotic relationship Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasi ...

; the common remora does not seem to have a negative overall effect on its host. The host provides the remora with fast-moving water to bathe its gills, a steady flow of food, transportation, and protection. The remora benefits the host by feeding in part on some of its parasites, but increases its hydrodynamical

drag Drag or The Drag may refer to: Places * Drag, Norway, a village in Tysfjord municipality, Nordland, Norway * ''Drág'', the Hungarian name for Dragu Commune in Sălaj County, Romania * Drag (Austin, Texas), the portion of Guadalupe Street adj ...

. The common remora's attachment to one host can last for up to three months. During this time, the remora can move its attachment site if it feels threatened. The common remora cannot survive in still water; it needs water flow over its gills to provide it oxygen.

Habitat

This remora is commonly found in war