We don’t typically think of ocean animals as having friends. And they don’t, really—not in the way we think of friends as folks you invite to happy hour and send pictures of your dog.
But they do have relationships where they help each other out. Today, the International Day of Friendship, we’re recognizing one of the many inter-species relationships in the sea: sharks and remoras.
If you’ve ever watched Shark Week, you’ve probably seen remoras hanging out alongside the sharks. Also known as suckerfish, they’re fish in the family Echeneidae that attach or swim alongside large marine animals like sharks. There are eight species in the family, and all are generally long and thin. The largest species is the slender suckerfish, which can grow to more than 43 inches, and the smallest is the white suckerfish, which grows only to about 12 inches.
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Remoras have a flat disc on top of their backs that functions like a suction cup (hence, “suckerfish”). They stick themselves to sharks, rays, whales and other large animals and cruise along. They’re sometimes referred to as the “hitchhikers of the sea.”
So what’s in it for remoras? These fish benefit by nibbling on parasites or grabbing leftovers from the sharks’ meals. The sharks aren’t harmed at all by remoras hitching a ride on their sides.
Recent research has helped us understand how remoras are able to stick so well to their hosts. Their suckers have collagen fibers that allow them to stick 3.5 times longer than the suction cups we’re used to.
This is a type of symbiotic relationship, or established interaction between two species where at least one species benefits. Other examples are coral and zooxanthellae, where zooxanthellae make food and get shelter, and cleaner wrasses and predatory fish, where the wrasses get a meal and larger fish get cleaned up.
We all get by with a little help from our friends—even ocean animals.