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Mutualism is a Win-Win for Ocean Animals

We get by with a little help from our friends—and so do ocean animals. Learn more about mutualism

Labroides_dimidiatus_by_Vincent_C._Chen
© Vincent C. Chen

The ocean can be a tough place to live, but some pairs of ocean critters have evolved to help each other out. The ocean is full of examples of mutualism, which is when two species interact and both benefit from the relationship. Let’s celebrate some of these dynamic duos!

Read on to see how ocean organisms work together to survive and thrive.

Coral + zooxanthellae: Coral polyps get their vibrant colors from tiny algae called zooxanthellae. Corals get food from the algae, which photosynthesizes like plants do, in exchange for housing and protecting the algae in their hard calcium carbonate structures. When corals get stressed by things like pollution or high temperatures, they kick out the zooxanthellae, which results in coral bleaching. Learn more >>

Cleaner wrasses + predator fish: Why would a little fish swim into the mouth of a predator? Because it’s a cleaner fish, of course. On coral reefs, large fish line up for “cleaning stations” where the wrasse removes parasites and dead tissue. The wrasse gets a meal, and the predator swims away healthier and happier. Learn more >>

Hawaiian bobtail squid + bacteria: Bobtail squid have a symbiotic relationship with a bioluminescent bacteria called Vibrio fischeri. The squid provides food for the bacteria it houses in a specialized light organ, and in turn, uses the bioluminescence for camouflage—the resulting blue-ish glow helps the squid blend in with the moonlit waters and avoid detection by predators. Learn more >>

Hawaiian bobtail squid
© Chris Frazee and Margaret McFall-Ngai

These are just a few of the many mutualistic relationships in our ocean. Others include gobies and mantis shrimp; manta rays and remoras; hermit crabs and sea anemones; groupers with octopuses and moray eels; and the famous sea anemone and clownfish. All are unlikely pairs who have found a way to help each other out, whether by sharing food, providing shelter or more. I mean, wouldn’t you say that only a true friend would pick parasites off of you?

Like the best of friendships, sometimes the relationship between these ocean critters can go through ups and downs—these ocean mutualisms may ebb and flow in their benefit to the ocean animals within them.

Learn more about wild and wonderful ocean animals with our fact sheets. Here are a few to get you started:

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