Clownfish and Sea Anemones - A Working Relationship

Clownfish are a prized addition to most any collector’s aquarium, as their bright colors are quite beautiful. However, in the wilds of the open ocean these small fish have little in the way of natural defenses, and there are plenty of hungry predators that would love to have them for lunch. What’s a clownfish to do? Find a much bigger best friend!

Clownfish share a symbiotic mutual relationship with sea anemones, predatory animals closely related to corals and jellyfish. The sea anemone inhabits coral reefs and uses its stinging tentacles to paralyze prey and enemy alike. Using fast-acting toxins for both offense and defense makes the anemone seem rather a self-sufficient creature, yet it harbors, even welcomes, the small tropical clownfish to take up residence among its tentacles.

The clownfish not only gets a wonderful living defense system from the anemone, but also an occasional meal from the scraps of fish the anemone fails to ingest. This relationship works both ways as the anemone will snack on any scraps the clownfish drops as well. The action of the clownfish also stirs up fresh water currents and moves them over the sedentary anemone.

So, how does the anemone know not to sting? There are a few different theories. One is that the anemone doesn't know, but that the mucus coating of the clownfish protects it from the anemone's toxins. This is possible because clownfish that have had this mucus wiped off of them have been stung and killed by their previous hosts. Another theory states that the chemical content of the mucus coating prevents the anemone from recognizing the clownfish as a food source, and therefore the anemone fails to react to the little fish's presence.