Remora fish, often called suckerfish, are recognizable hitchhikers found in warm tropical and subtropical waters worldwide. These streamlined marine animals are famous for their unique ability to attach themselves to much larger sea creatures. Remoras commonly cling to hosts like sharks, whales, and sea turtles, using them for transportation and resources. This behavior raises the question of whether these travelers pose any threat to humans.
Understanding Commensal Behavior
The remora’s role in the marine environment is a classic example of commensalism, a symbiotic relationship where one species benefits while the other is generally unaffected. Remoras are not predatory fish; their survival strategy is built around scavenging. Their diet consists primarily of small prey, plankton, and food scraps dropped by their host during a meal.
They also perform a cleaning service by consuming external parasites and dead skin from the host’s body. This search for free meals means the remora lacks the aggressive hunting instincts or powerful jaws that would make it dangerous. Hitchhiking saves significant energy, providing a clear benefit without harming the host.
Assessment of Human Risk
Remoras are not considered dangerous or aggressive to humans, as they have no venom or offensive biting capabilities. Their interest in a diver or swimmer is usually driven by curiosity or the mistaken perception that a human is a potential host or a source of food scraps. Instances of a remora attaching to a person are rare, but when they do occur, they are generally harmless.
Any potential “harm” is typically limited to mild pressure or minor abrasions if the fish is forcibly pulled away. The strength of the attachment can make removal difficult, but the fish does not bite defensively. The sensation of a remora attaching is described as a strong suction cup pressing against the skin, which is more startling than painful.
The Anatomy of Attachment
The remora’s ability to cling to surfaces comes from a highly specialized structure on the top of its head. This oval-shaped organ is not a mouth or a separate suction cup, but an evolutionarily modified first dorsal fin. The disc contains numerous rows of movable, slat-like structures called lamellae, which are supported by bony elements derived from fin spines.
When the remora presses the disc against a surface, the fleshy outer lip forms a tight seal, and the lamellae are raised to create a powerful vacuum. The lamellae also possess tiny, tooth-like projections called spinules that enhance friction, helping the fish maintain its hold even on the smooth, fast-moving skin of a host. This mechanism is designed purely for temporary adhesion and transportation, not to penetrate or cause injury.