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The darting and playful clown fish are probably the most recognizable tropical fish with their orange and white stripes. Almost never separated from its host anemone, the clown fish participates in the famous symbiotic relationship where each protects and benefits the other. The small fish love warm waters and active coral reefs where they are sure to find an anemone and plenty of food.
Clown fish, also called anemonefish and damselfish, are found across the Indian and Pacific Oceans and the Red Sea. They inhabit reefs off the coasts of Australia, Borneo, Papua New Guinea, and the Solomon Islands. Ideally, Amphiprioninae prefer temperatures of 70-80° F (21-27°C). They'll grow to 2-4" (5-10 cm) long when healthy. Humans pose the largest predatory threat, as they collect the appealing fish for sale as aquarium pets.
Although there are many species, most clown fish have the distinctive markings of two or three white stripes against a background of orange, red, or yellow. Their two dorsal fins, two bottom fins, and two pectoral fins are fringed with a deep black, velvety edge.
Perhaps the most remarkable aspect of the clown fish is its symbiotic relationship with an anemone. Anemones are creatures somewhere between a plant and an animal that's attached to a rock or sandy ground. Its stinging tentacles paralyze fish swimming by, and a central stomach digests them. The clown fish, immune to the poison, keeps close to the tentacles to eat the leftover fish pieces and clean the anemone. In turn, the anemone's toxic reputation keeps predators away from the clown fish.
No one knows exactly why an anemone's poison doesn't affect the clown fish. The fish can cover itself with thin mucus that might insulate it from the full force of the toxic chemicals. It also might individually adjust itself to its host anemone by allowing itself to be stung with gradually increasing intensity until it has developed a personal immunity. This might account for the quick, whipping dance it does amongst the forest of brightly colored tentacles.
Another fascinating aspect of the clown fish is its ability to switch sex within the community's hierarchy. At the top of the mating hierarchy is the reproducing female. Underneath her is the lead male, who mates with her, and a bunch of other non-mating males. If the female dies, her absence disrupts the hierarchy. Therefore, the lead male will morph into a female, and her mate will be chosen from among the other males, thus restoring order.