The Clownfish is surely everybody’s favourite fish? It may also be one of the cleverest. It is one of just a few fish that can make itself immune to a sea anemone’s sting.
Unlike other fish, the Clownfish is able to swim freely between the poisonous tentacles of an anemone without being stung. This gives them protection and is a very good reason to take up residence! In fact, most Clownfish spend their lives living in small groups within easy reach of ‘home’.
But what about breeding time? If they never stray far from home, how do they meet other Clownfish? The answer, of course, is stranger than fiction.
Clownfish communities usually consist of a breeding pair and a few non-reproductive, younger and smaller males. When the female dies the larger male changes sex and takes the place in the shoal as the female. This is because all clown fish are born male. This is known as being a protandrous hermaphrodite.
Clownfish lay their eggs in large batches on flat surfaces near to their host anemone, usually around the full moon. Depending on the species, this could be hundreds or thousands of eggs. The male parent will usually guard the eggs until they hatch about 6 to 10 days later. This usually happens about 2 hours after dusk. Once the eggs have hatched the male will usually stay to take care of the young until they reach sexual maturity.
Don’t be fooled by Hollywood though. The truth about them is that they are extremely territorial and aggressive fish and enjoy a very special entente cordiale with their host. Basically they help each other in their quest for survival. The Clownfish will eat the remains of fish paralysed and eaten by the anemone and, in return, keeps the anemone healthy by eating any rotten or damaged tentacles. The Clownfish will also feed on small, invertebrates that could harm the anemone whilst the Clownfish’s excrement will provide nutrients to the anemone. It’s a beautiful relationship!
Whenever a Clownfish takes up residence in a new anemone it performs an elaborate dance, during which it gently touches the tentacles with parts of its body. This could be the way the fish acclimatises itself with the anemone so it doesn’t feel the stings.
Clownfish live in the warmer waters of the Indian and Pacific oceans, including the Great Barrier Reef and the Red Sea. The largest can reach a length of 18 cm (7.1 in), while some can be as small as 10 cm (3.9 in).
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