Why do clownfish live safely among sea anemones?

Clownfish can live among sea anemones because their skin is covered with a mucus layer that prevents the anemone’s stinging cells, called nematocysts, from firing. Scientists have found that the fish also slowly acclimate to a host anemone, which helps reduce the chance of being attacked. The relationship is mutualistic: clownfish gain shelter from predators, while anemones may benefit from nutrients, grooming, and protection from some predators. This partnership is famously associated with Indo-Pacific reefs and was popularized worldwide by the orange clownfish, Amphiprion ocellaris. The exact mucus chemistry varies by species and host, which is why many clownfish are picky about which anemone they can safely use.