Is the relationship between a anemone and a clown fish interdependent?

For protection, clownfish seek refuge amongst the tentacles of sea anemones. The tentacles contain harpoon-like stinging capsules called nematocysts that the anemones employ to capture prey and ward off predators.

In a yet-to-be resolved biological mystery, clownfish have mucus on their skin that somehow protects them against the sting of their host anemone. As a result, the clownfish are able to stick near their host which is avoided by most other fish in the sea.

'The clownfish gets protection by hiding sting-free among the tentacles. If you remove the clownfish, large butterfly fishes will eat the anemone,' said John Randall, an ichthyologist at the University of Hawaii at Manoa.

Butterfly fish are predators of the sea anemone. In certain areas of the tropics where clownfish, sea anemone, and butterfly fish exist, clownfish scare off butterflyfish from their host anemone. Research has shown that if the clownfish are removed from the anemone, butterfly fish will move in and devour the anemone. So, the protection of the anemone afforded by the clownfish is part of the mutual relationship.

In addition to scaring off predators, some scientists speculate that clownfish waste may serve as a nutrient for the anemones…

There are more than 1,000 species of sea anemones found throughout the world's oceans. Only ten of these species share their niche with clownfish, which thrive in the tropical waters of the Indian and Pacific oceans.

Each individual host anemone is home to one group of clownfish, which contain a dominant breeding pair and up to four smaller, subordinate fish. There are 28 known species of clownfish, so more than one species of clownfish may take to any given species of anemone.