Anemones have stinging cells called nematocysts that keep away most predators. The protein toxins that are released are ichthyotoxic; if marine or freshwater fish are exposed to .5 micrograms/mL of the toxin, they die within 2 hours.
Magnificent sea anemones are hosts to many symbiotic clownfish, which chase away any nibbling predators, especially bristle worms. The clownfish are immune to the nematocysts and gain protection from the anemones' stinging tentacles.
- Mebs, D. 1994. Anemonefish symbiosis: vulnerability and resistance of fish to the toxin of the sea anemone. Toxicon, 32 (9): 1059-68. Accessed May 17, 2011 at http://www.ncbi.nlm.nih.gov/pubmed/7801342.