The Clownfish’s Affinity for Sea Anenomnes

©istockphoto/RapidEye

The relationship between a clownfish and its sea anemone goes hand-in-hand―or rather fin-to-tentacle.

A Curious Relationship
For years, marine biologist and fishkeepers alike knew that clownfish were using sea anemones as protective homes, eluding any would-be predators within the anemone’s stinging tentacles. But there in lies an ever-present coral conundrum—how are the clownfish able to co-habitat within those otherwise venomous cnidarians without injury? And it boils down to one anatomical asset—mucous.

Clownfish—through their evolutionary mutualism with these anemones—have developed a unique specific outer mucosal layering that retards the nematocyst—the cellular body responsible for administering that “sting” via a projected needle into the would-be threat’s epidermis—from firing-off. Mother Nature, your genius is awe-inspiring.

Mutually Beneficial
But what’s more interesting is that this isn’t a beneficially “one way street”—there’s a fork in the road. Clownish have been observed preforming what scientist call the “wiggle dance” for years and were, like the mucosal-laden epiphany described beforehand, baffled as to how the ritual came to be. The answer is quite simple, ironically: circulation. Sea anemones often find themselves in somewhat stagnated currents, and this quirky dance, preformed solely by clownish, aids in circulating oxygen-rich water to-and-from the anemone’s tentacles.

Leaving the Nest
Much like in a favored Pixar film, some young clownfish (actually still larvae) leave their birth place and embark on long journeys to find a new home. Marine biologist have been aware of the genetic drift found in clownfish communities for years, but the distance these near-invisible fish took to find their stinging sanctuaries was unknown, until now. Larvae, measuring only a few millimeters in length, have been documented traveling upwards of 250 miles in order to find a new coral community. That being said, numerous newly-hatched individuals are perfectly content finding new niches to populate within their endemic reef systems—only about 6% of larval clownfish well embark on such Pixar-reminiscent journeys.

Nothing Like Home
Anemones secrete olfactory queues to the fish embryos which are growing in or near them. What that means for the fish is when it hatches, if it was introduced to those olfactory queues while an embryo, it’s more likely to stay there for the duration of its life. Coincidentally, fish that weren’t exposed to those smells of a host anemone from the get-go are more likely to seek out new coral niches.