The sea anemones and the clown fish are well known to be a mutualistic pair and lot of research have been done about this pair of symbionts. We can also say that this relationship is a near perfect one in all aspects. Mutualism is an ecological interaction between two organisms in which both gain increased survivorship as a result of the interaction.
The mutualism between the clown fish and the sea anemones is one such example. The 26 species of clown fishes from two genuses; 25 from the genus Amphiprion and 1 from the genus Premnas, are obligate symbionts of the 10 species of sea anemones which belong to two main genera Stichodactyla and Heteractis. Usually only fish of one species occurs within one actinian but there are also cases where 2 of them share a host which will usually be a large one with different territories for the 2 species.
Clown fishes and sea anemones are under an obligate mutualism. This means that their range both ecologically and geographically does not really extend beyond their host. The stinging tentacles of the anemone protects the clown fish from the predator fishes. The clown fish is the only one which does not get stung by the tentacles since it has a mucus covering for protection. It was discovered that the clown fish do not really attach themselves to the tentacles but swim among them and huddle inside them for protection. Since the sea anemones pretty much fixated to the area they are in and are not very mobile, the clown fish helps to defend their territory and also eats the left overs from fish on the tentacles. The clown fish is provided with food by the anemone and in turn the clown fish give a better circulation of water to the anemones since they fan their fins while swimming about. The feces of the clown fish is also used as fertiliser by the anemone.
1) Fautin, D.G, 1991. The AnemoneFish Symbiosis: What is Known and What is Not. Symbiosis 10: 23-46
2) “Please use captive raised Clown Fish hosts” by Trevor. Anemones and Clown Fish, 7 Sep 2003. URL: http://www.garf.org/trever/anem/anenome.html (accessed on 16 Apr 2010).
3) “An exploration of the Clownfish” Author Unknown. Clownfish Biology, Oct 2005. URL: http://tolweb.org/treehouses/?treehouse_id=3390 (accessed on 16 Apr 2010).