If you’ve seen the movie Finding Nemo, you may remember that clownfish live in an anenem… an ananemon… an anemone. Indeed, clownfish, more properly called anemonefish, make their homes inside an animal called an anemone. So what do you really know about these fish, and the animals they live in? While the movie did get a lot right, the facts surrounding these amazing animals may surprise you.
To begin with , let’s look at the anemonefish. Inside any anemone inhabited by anemonefish, the largest fish is the dominant female. Her job is to lay the eggs. That’s it; as soon as the eggs are laid, it is the job of the smaller fish, the male, to guard them from predators. Clownfish are sequential hermaphrodites, meaning that when they hatch from their eggs, they are all male. If the female clownfish is removed from the group, such as by death, one of the largest and most dominant males will become a female. The remaining males will move up a rank in the hierarchy.
Now, let’s take a look at the anemone. Sea anemones are in the same phylum, or general group, as jellyfish and corals. They have a very simple body structure, made of a base with many tentacles. Each of these tentacles has millions of tiny stinging cells, called nematocysts. These cells are used both for defense and to catch tiny prey. So how do the clownfish manage not to get stung? Clownfish, Cardinalfish and certain damselfish are among the few species of fish that can avoid the potent poison of a sea anemone. There are several theories about how they can survive the sea anemone poison. One theory is that the mucus coating of the fish may be based on sugars rather than proteins. This would mean that anemones fail to recognize the fish as a potential food source and do not fire their nematocysts, or sting organelles. Another theory is that the coevolution of certain species of clownfish with specific anemone host species and may have acquired an immunity to the nematocysts and toxins of their host anemone.
So when you come to the reef, keep an eye out for Nemo; with over 27 different species of anemonefish at the Great Barrier Reef, you’re bound to find him or one of his cousins. Look in flat areas on boulder corals, where anemones tend to settle. Just remember, it is best not to touch the anemone or any of the coral, as it can sting and cause permanent damage.
Remember: We have one reef; let’s take care of it!