What Counts in the End

Mr. & Mrs. Nemo

Don’t let the cheery and colorful scenery fool you: Life in the coral reef is tough! Deadly predators equipped with sharp teeth or reinforced blades perpetually patrol the area, and the prettiest creatures emit one of the most fatal neurotoxins. If you want to survive here as a small fish without resorting to offensive warfare, you’ll need nerves of steel, reliable allies— and a really good plan! The clownfish has all three. It spends its entire 10- year existence right in the midst of the aforementioned poisonous creatures, the sea anemones. Clownfish and certain species of sea anemones engage in a symbiotic relationship: The stinging toxic nematocysts on a sea anemone’s tentacles offer clownfish protection from predators, and in return the colorful clownfish will bring their landlords nutritious tidbits now and again and also keep their anemone’s tentacles clean and healthy.

To keep from falling victim to the deadly tentacles, clownfish wear a protective mucus coat and will also gently brush up against anemone tentacles several times to acclimate themselves. This means the sea anemone will no longer regard the fish as intruders. This is how the clownfish signal: “I belong to you, I pose no danger— and I am not something to eat.” In the center of sea anemone, Mr. Nemo surveys his 1,000 eggs each day. Yes, Mr. Nemo— for clownfish, the males care for the offspring. Clownfish believe in a defined hierarchy— being the boss is a good thing. In practice it looks like this: Five male fish report to a lead female. They all live together on a sea anemone. As soon as any fish dies, the survivors move up the ranks by one position. If the dead fish happens to be the female, the dominant breeding male will have to take her place as the boss. The female boss. Because reaching the top of the heap has its price: The male has to mutate— by way of an automatic sex change, it becomes a female. That’s because it’s clownfish females that rule the reef.