giant carpet anemone (Stichodactyla gigantea) and (within the hobby) the bubble-tip anemone (Entacmaea quadricolor). However, if these anemones are not available, clownfish are known to take host within similar corals, such as those in the genus euphilliidae. This relationship is symbiotic as both members benefit: the clownfish is provided shelter and safety from predators by the anemone’s powerful sting. The clownfish also uses the anemone in order to obtain food: they do this by luring larger fish into the anemone, and then letting it get killed by nematocysts, and feasting on the remains. The anemone is provided both the clownfish’s waste products and its protection from predators such as butterflyfish. Why are clownfish not stung by anemones? The clownfish themselves avoid being stung by their host anemone. There are currently many opposing hypotheses as to why this occurs. However, there is some general consensus that a crucial factor would lie within the thick mucus coating which envelops the clownfish, as the flesh of the clownfish cannot withstand the sting of an anemone. The most widely believed theory states that the anemone is a passive partner, rather than reacting differently in the presence of a clownfish. It instead argues that the clownfish’s thick mucus coating is produced by the clownfish when it comes into contact with the anemone, and does not trigger a different chemical response from the nematocysts, but instead that the coating itself is enough to prevent the firing nematocysts from causing harm to the clownfish [21]. A study showed that, when clownfish were removed from their anemone and returned 1-3 days later, they would be stung for a period of acclimation to the anemone. Another theory suggests that the anemone produces quantities of protective substances. Whilst non-symbiotic fish would rarely come into contact with the anemone, and thus would be stung, symbiotic fish would repeatedly rub on the anemone to acclimatise, and therefore acquire some of the defensive substances which incorporates into their mucus [22]. This could either be the anemone recognising the fish as symbiotic, or as a part of itself, due to the common antigens. A test showed that clownfish which came into contact with anemones contained antigens within their mucus which were anemone-exclusive. How do clownfish know to find an anemone? Clownfish seem to have an innate sense of guidance towards finding an anemone, as an evolutionary factor where the clownfish finds the anemone by chemical signalling. However, a test showed there is also some form of imprinting which plays a factor in the ability of a clownfish to recognise an anemone. Eggs from Amphiprion ocellaris were raised in two environments: one in the presence of a host anemone, and one without. When moved into an environment with an anemone and hatched, the larvae which had been reared in the presence of an anemone immediately found the anemone within 5 minutes, whilst the ones which had not did not find it within a 48 hour time period. However, a study also showed that the innate guidance appeared within the fish once reaching the stage of development where the fish would look for settlement. In a different test, which involved two compartments of water connected by a Perspex flume. One of the bodies of water contained “anemone seawater” (water that had been in a tank for 12 hours with a host anemone. The clownfish of different development stages were added and then measured as to which body of water they would prefer to stay in. The results showed that the majority of the clownfish, at every stage of development would prefer to stay within the “anemone water”. I believe that imprinting or environmental factors must play a large role in the locating of a host. In the school marine tank, within the 3 months, our clownfish have failed to
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