Common Remora
Remora remora
A remora uses the sucking disk on top of its head to attach itself to larger marine animals like sharks, rays, and sea turtles — where it can stay for 3 months. The host provides the remora with protection, food, and a fast flow of water over its gills, which the remora needs in order to survive.
A Clingy Fish
The flat disk, which a remora uses to attach itself to other animals, is a specially adapted dorsal fin.
Few other fish could boast of a head that doubles as a suction cup. There are eight species of remora (all in the family Echeneidae), that live in tropical open-ocean waters — however, they have been found in temperate waters too, brought along by the larger animals they've suctioned to. And 'suctioned' is the right word. The flat, ovular disk on a remora’s head was once its front dorsal fin. Made out of a flexible membrane, this sucker has slat-like structures that can open and close to create suction, allowing it to adhere to flat surfaces. If the ride gets rough, the remora can increase its suction by sliding back and if it feels like it's reached its stop, it can slide forward to release — a remora will also often reposition itself on its host's body if it feels unsafe.
A remora detaches itself to snatch up the bits and pieces of food that its host has carelessly missed, but it may also eat plankton and small fish — as well as parasites that infest its host's body. More recently, it has been suggested the remora may sustain itself on the faeces of its host, however, this claim is slightly dubious.
Friend or Parasite?
A group of remora following their shark host.
Is the remora a friend to the larger animals on which it hitches a ride or is it a freeloading parasite? While it may seem like it's taking advantage of its hosts — like a friend that sits in your car, insists you take him wherever you go, and snatches up your leftover food scraps — the remora may not actually be parasitic. Many consider it to be a commensal fish, meaning that the remora benefits without either helping or harming the host (the relationship may specifically be phoresy; where one animal temporarily travels on the body of another without being a parasite). Others suggest that the relationship is mutualistic; the remora gets a ride and protection, while the host gets a cleaning — the remora eats the parasites off of the host's body. Whether the benefit of removing potentially disease-causing parasites outweighs being slowed down (through hydrodynamical drag) by a bodily hitchhiker for months at a time is up for debate.
Can we get the opinion of one of its hosts? An alternative name for the common remora is the "shark sucker". So, do sharks appreciate this close companionship? Unfortunately, it's unknown if sharks just tolerate these clingy fish or just aren't swift enough to catch them. However, few remora have ever been found in a shark's stomach — although some smaller ones have been found inside a shark's mouth, clinging to the roof. Some observers have even reported that sharks will slow down to accommodate for the remoras. A win for friendship? Maybe, but the remora might also just be too small — growing between 30 to 110 cm (12 - 43 in) long, depending on the species — to be worth the sharks' efforts to catch and eat it. It may come down to the species of shark; while some, like sandbar and lemon sharks, act aggressively towards remoras, others don't seem to mind their super-dependent disposition.
Where Does It Live?
⛰️ Warm tropical waters; usually clinging to larger fish, turtles, or marine mammals.
📍 Cosmopolitan in warm waters. ¹
‘Least Concern’ as of 23 August, 2012.
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Size // Medium
Length // Common remora grows up to 86 cm (34 in), other species from 30 to 110 cm (12 - 43 in)
Weight // Common remora around 1.1 kg (2.4 lb), others species around 1 kg (2 lbs)
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Activity: Diurnal ☀️
Lifestyle: Solitary & Social 👤👥
Lifespan: 2 - 8 years
Diet: Carnivore
Favorite Food: Food scraps and ectoparasites from its hosts 🦈
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Class: Actinopterygii
Order: Carangiformes
Family: Echeneidae
Genus: Remora
Species: R. remora
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The remora's suction cup was once its dorsal fin. Its new function — sticking to larger animals — is achieved by slat-like structures that can open and close to create suction. The remora can slide backwards to strengthen the suction and swim forward to release itself.
Remoras will suction themselves to many host organisms; including larger bony fish, sharks, rays, sea turtles, and marine mammals.
While they prefer warm tropical waters, remoras have been seen in more temperate water too — likely brought there by their travelling hosts.
There are eight species of remora, in the family Echeneidae.
The smallest remora is the white remora (Remora albescens), growing to only 30 cm (11.8 in) long, while the largest is the live sharksucker (Echeneis naucrates), which can be as long as 110 cm (43.3 inches). The common remora, measuring up to 86 cm (34 in) long, is somewhere in between.
The relationship status between a remora and its host is a disputed topic. Some propose the relationship is mutualistic (the remora gets a ride and food scraps while cleaning its host's parasites, both benefiting), others say that it's parasitic (the remora slows its host down and wastes its energy without providing any benefits to the host), while others say it's commensal (the remoras actions don't positively or negatively affect its host).
