I have always been very interested in maintaining aquariums at home. I first started off with freshwater aquariums but now I have moved on to maintaining a more challenging saltwater aquarium. One of the most intriguing aspects of my aquarium is the relationship between my clownfish and anemone.
Sea anemones are Anthozoans, which belong to the phylum Cnidaria. What often catches my eye the most is their gorgeous appearance due to their tentacles. As elegant as they may look they can be dangerous because the tentacles contain many cnidocytes. Cnidocytes are stinging cells that help the anemone catch its prey and defend itself from any predators. To catch its prey the anemone discharges nematocysts, which paralyzes and kills its prey. Also, if the anemone feels threatened by a possible predator, these stinging cells are discharged and sting the predators so that they know not to mess with it anymore (Kass-Simon and Scappaticci 2002).
The anemone that lives in my aquarium is a Condylactis gigantean, which lives in tropical waters and is a very common type of anemone found in the wild. It can only be seen in the Atlantic Ocean as this is their primary habitat, and likes to inhabit shallow waters (Cairns et al. 1991).
Figures 1 and 2: Condylactis gigantea anemones and associated clownfish, Amphiprion ocellaris, in my aquarium.
Photo Credit: Carlos Carranza
The two species of anemone I keep in my home aquarium are shown above (Figure 1). As you can see they may be found in various colors: purple, green, white and many more. Of the two, Condylactis gigantean, are known to be especially territorial and aggressive towards other anemones, corals and fish. Due to this, the many other organisms in my tank must take precaution. But there is one organism that stands out and does not need to be too careful; in fact, it spends a lot of its time interacting with my sea anemone. This organism is the clownfish.
Clownfish contain a special slime coat that allows them to touch the anemone and not get stung (Fautin 1991). The pair has a very unique symbiotic relationship where each of them benefits from the other. This is also called a mutualism, because both organisms benefit and do not get harmed from their relationship. The clownfish hides in the anemone as a way to stay free of predators: if any predators tried to get through the anemone to get the fish then they would get stung and paralyzed. Having a clownfish around benefits the anemone because it can feed off of the nutrients found in the clown fish’s fecal matter, and the clownfish can also bring the anemone food. Another benefit for the anemone is that by swimming around it, the clownfish increases local water flow, which allows the anemone to take in more oxygen. Though anemones have stinging cells for defense, some predators can eat them. For example, the Butterfly fish is known to eat anemones. Clownfish provide further benefit, as they fight these predators off (Fautin 1991). To obtain all of these benefits, all the anemone is responsible for is using its stinging cells as a way to keep the clownfish safe. Anemones can survive just fine with out the addition of symbiosis, but with it their ability to attain food and defend its self only increases.
Figure 3: Anemone hosts Maroon Clown.
Photo Credit: Carlos Carranza
References
Cairns, S.D.; Calder, D.R.; Brinckmann, A.; Clovis, C.B.; Pugh, P.R.; Cutress, C.E., Jaap, W.C.; Fautin, D.G; Larson, R.J.; Harbison, W.C.; Arai, M.N.; Opresko, D.M. Common and scientific names of aquatic invertebrates from the United States and Canada: Cnidaria and Ctenophora. American Fisheries Society Special Publication 22. Maryland: American Fisheries Society, 1991.
Fautin, D. G. 1991. The anemone-fish symbiosis: What is known and what is not. Symbiosis. 10(1): 23-46.
Kass-Simon G., Scappaticci A. A. Jr (2002). The behavioral and developmental physiology of nematocysts. Canadian Journal of Zoology 80: 1772–1794. doi:10.1139/Z02-135.
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