The weird and wonderful world of the clown fish
It’s hard being a clown fish. You’ve got kids to keep an eye on, razor-sharp coral to watch out for and dangerous predators at every turn. Oh, and there’s the small matter of a sex change just around the corner
Don’t be fooled by the colourful scenery: it’s a tough life in amongst the coral reef! There’s danger everywhere you look – some of the coral has razor-sharp teeth, others are armed with deadly blades – while predators constantly patrol the surrounding waters. It’s a world of contrasts: the prettiest-looking plant contains some of the most fatal neurotoxins.
To survive here as a small fish you’ll need nerves of steel, reliable allies – and a really good plan. Luckily, the clownfish has all three of these qualities. It spends its entire ten-year existence slap bang in the middle of the sea anemone, one of the reef’s most poisonous plants. Theirs is a symbiotic relationship, beneficial to both partners: the toxic tentacles of the anemone protect the clownfish from predators, while in return the colourful fish pushes its host something nutritious every now and again and keeps its tentacles clean.
So that it doesn’t fall victim to the deadly tentacles, the clownfish familiarises itself with them by gently brushing against the tentacles several times. The fish then coats itself in mucus so that the sea anemone doesn’t see it as an intruder. In effect, the clownfish is saying, “I belong to you, I’m harmless, there’s nothing to eat here.”
In the centre of the sea anemone, Mr Nemo watches over 1,000 eggs every day. That’s right, Mr Nemo – with clownfish, it’s the men who look after the kids. They’re also an integral part of a plan that is as ingenious as it is unique: clownfish believe in a size-based hierarchy – big is best. In practice it looks like this: the male fish all report to a lone, large female. The breeding male is second largest in the group, and the others get progressively smaller as the hierarchy descends. All live together on a sea anemone. As soon as a fish dies, the survivors move up the ranks by one position. If that fish is also the female, the breeding male changes sex and assumes the mantle of leader. The largest non-breeder then becomes the breeding male and so on. Complicated? Not really. You just need to remember that with clownfish it’s always the female that rules the reef…