When disturbed the least toxic anemone, H. malu, has the ability to completely withdraw beneath the sand and can remain hidden for at least 2 days. Conversely, C. adhaesivum, the most toxic anemone, does not exhibit this escape response when disturbed. In this case the high toxicity level of C. adhaesivum may be sufficient as a defense strategy against grazers so that withdrawal under the sand is not required. It is likely that an upper toxicity threshold exists for anemonefish species to establish tolerance to venom without being harmed. As C. adhaesivum has only a single anemonefish symbiont living within it, might indicate that it is close to the upper limit. Lubbock has suggested that A. clarkii has a thicker mucus layer than other anemonefish species, which may be an adaptation for this purpose. Low anemone toxicity levels are also unlikely to be optimal for anemonefish survival. Interestingly, only juvenile anemonefish are known to associate with H. malu, the least toxic anemone in our sample. Similarly, H. aurora, also on the lower than average toxicity level only has juvenile anemonefish associates,,. Juvenile anemonefish are far less likely to hold valuable KT109 resources when competition exists for anemones, therefore are likely excluded from high quality anemones and pushed into lower quality anemone species. Similarly, Fautin, suggests that E. quadricolor is the most OG-L002 hydrochloride desirable anemone host because it has the highest number of symbionts. Our results support this claim and suggest that E. quadricolor possesses optimal toxicity for anemoenfish survival which is further supported by the large number of highly competitive anemonefish species that use it, as well as the highly specialized anemonefish species that use it exclusively in the wild. The factors influencing survival are likely complex, but such a strong preference for E. quadricolor by anemonefish signifies the potential fitness benefits that higher quality anemones must afford their symbionts, and as Fautin has shown competition for these valuable resources is high.