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.
Not many fish could boast of a head that doubles as a suction cup.
There are eight species of remora that live in tropical, open oceans around the world. However, these sleek-bodied fish have also been found in temperate waters, ferried along by the larger animals onto which they suction. And “suction” 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 backwards and if it feels it's reached its stop, and wishes to disembark, it can slide forwards to release itself — a remora will also reposition itself on its host's body, like moving to a better seat on a bus.
Its host also provides onboard meal service. A remora will detach itself to snatch up bits and pieces of food that its host has carelessly missed, or eat plankton and small fish — as well as parasites — that infest its host's body. More recently, it’s been suggested that the remora may sustain itself on the faeces of its host. However, this claim, much like the nutritional value of such a meal, is a little dubious.
Friend or Parasite?
A group of remora following their shark host.
Is the remora a friend to the animals on which it hitches a ride or is it a freeloading parasite? While it may seem to take 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 so bad. Many consider it to be a commensal fish, meaning that the remora itself benefits without either helping or harming its host — more specifically, the relationship may be phoresy, wherein one animal temporarily travels on the body of another without harming them. Others suggest that the relationship is mutualistic; the remora gets a ride and protection, while the host gets a cleaning (with the remora eating potentially disease-causing parasites off of the host's body). But whether the benefits of a parasite cleanse outweigh dragging along a bodily hitchhiker for months at a time, possibly hampering speed and increasing energy expenditure, is up for debate.
Can we get the opinion of one of its hosts?¹ Common remoras (Remora remora) are also known as "shark suckers". So, do sharks appreciate their close companionship? Unfortunately, it's hard to tell if sharks tolerate these clingy fish or are simply not fast enough to catch them. Very few remora have been found in a shark's stomach — although some smaller ones have been found inside a shark's mouth, clinging alive to the roof. Some observers have even reported that sharks will slow down to accommodate for the remoras’ swim speed, allowing them to catch up and latch on. A win for friendship? Maybe. Alternatively, the remora might just be too small — growing between 30 to 110 cm (12 - 43 in) long, depending on the species — and fast to be worth a shark’s effort to catch and eat it. It may also 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 dispositions.
¹ While sharks are a common host for remoras, these sticky fish will also latch onto rays, large bony fish, sea turtles, whales, and dolphins — the live sharksucker (Echeneis naucrates) is even known to suction onto scuba divers.
Where Does It Live?
⛰️ Warm tropical waters; usually clinging to larger fish, turtles, or marine mammals.
📍 Cosmopolitan in warm waters. ¹
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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).
‘Least Concern’ as of 23 August, 2012.
