The ocellaris clownfish (Amphiprion ocellaris), is one of the most common clownfish among the 30 separate species known of at this time. Like many reef fish, they are sequential hermaphrodites, meaning that they are all born male, but some do change their sex and become female once they have reached maturity.
Clownfish are also known as anemonefish, due to their symbiotic relationships with sea anemones. There are multiple theories as to how the clownfish has evolved to be coated in a specific mucus that makes them immune to the toxic stings of sea anemones. Regardless of how it has come to be, the clownfish benefits greatly from this immunity which allows them to make their homes among the stinging tentacles of sea anemones, where many predators do not dare go.
Anemones also benefit greatly from the efforts of the fish. Clownfish are very protective of their anemones and are known to even (harmlessly) attack curious divers and snorkelers who get too close. Ammonia are often fed bits of food by clownfish whose waste fertilizes them, and the nearly constant swimming and twitching of the clownfish provides the aeration needed by the anemone to thrive.
Clownfish are not the only fish who enjoy symbiosis with anemones. Others who do include cardinalfish and incognito gobies, sometimes called anemone gobies. We photographed this clownfish while diving near Sekotong, Indonesia. Read more in our post, A Scuba Divers Guide to Lombok, Indonesia.