A Blue View: Clownfish

Published April 09, 2014

by John Racanelli, Chief Executive Officer

A Blue View is a weekly perspective on the life aquatic, hosted by National Aquarium CEO John Racanelli.

From the smallest plants and animals invisible to the human eye to entire ecosystems, every living thing depends on and is intricately linked by water.

Tune in to 88.1 WYPR every Tuesday at 5:45 p.m. as John brings to the surface important issues and fascinating discoveries making waves in the world today.

April 9, 2014: Clownfish

Click here to listen to John discuss clownfish and the important role they play in the health of coral reefs!

Parents of young children know a thing or two about clownfish. These adorable orange and white fish rocketed to stardom in the animated classic Finding Nemo, which featured an adventurous clownfish hero.

Finding Nemo

Clownfish popularity, however, extends far beyond the preschool set. The movie led to an upswing in their demand within the exotic pet trade - they are now one of the most popular saltwater aquarium fish.

That was the downside of the Nemo-effect. The upside? More people became interested in coral reef conservation. It is an ecosystem of tremendous importance, fragility and interdependence, and clownfish are an indicator species for reef health.

Further, they are truly fascinating creatures. When Nemo's dad, Marlin, names all of the eggs Marlin Junior, the moviemakers got the science right: all clown fish are born male. Many fish species are able to change sex, almost always from female to male. But the clownfish is different, changing gender only to become the dominant female of the group, and that change is irreversible. In a clownfish group living in an anemone the largest fish is female, the second largest a male. They are the mating pair.

But the adventure story of Nemo's dad traveling far and wide to find his son? Unscientific. In the wild, clownfish never venture far from their anemone. It's home...and pantry. It's this interdependence that has earned the fish their full name: the anemone clownfish. national aquarium clownfish

The relationship between anemones and anemone clownfish is a classic oceanic partnership of mutualism.

In science, mutualism is defined as a relationship between two species in which both benefit from the association. In fact, clownfish and anemones probably couldn't live without each other, which qualifies them as "obligate symbionts."

They couldn't be more different, yet they need each other to survive. The clownfish is a vertebrate, while a sea anemone is an invertebrate, closely related to corals and jellyfish. And like them, its sting is deadly to most other creatures.

So how does the clownfish manage to live among the anemone’s lethal tentacles? Well, very cautiously. As the clownfish gets to know its anemone, it does an elaborate ballet of tentative darting movements, touching the anemone's stinging tentacles gently, working up immunity and a protective layer of mucus.

Once they've acclimated to each other, they eat each other's food scraps. The anemone's tentacles provide the clownfish with protection from predators. The clownfish protects the anemone from predators like the butterfly fish and nibbles the anemone free of parasites. Cozy, right?

But scientists have recently discovered that there is additional complexity to the relationship.

The anemone benefits from the clownfish's ammonia-rich waste. It’s like anemone fertilizer: it helps the animal grow.

After all, a bigger anemone is better for both; its larger tentacles can snare larger, more nutritious prey and the clownfish gets better leftovers and more spacious living quarters.

There's also a fascinating nocturnal half to the anemone-clownfish routine. Scientists used to think that at night the clownfish snuggled quietly inside the anemone. But Dr. Nanette Chadwick and her team at Auburn University recently discovered that the clownfish moves around more than was suspected, reminiscent of a dog trying to get comfortable on its dog bed.

The clownfish's movements oxygenate the water deep within the anemone's tangle of tentacles. In effect, the clownfish helps the anemone breathe.

Clownfish and anemones literally cannot live without one another. In the sea, as in Hollywood, they call that chemistry!

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John Racanelli

Chief Executive Officer

National Aquarium - John Racanelli

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