One of the most visible examples is
the interaction of sea anemones and anemonefish in the
coral reefs of the Indo-Pacific (Fig. 1). Fautin and Allen
(1997) list 26 species (previously 28, but 2 were found to be
hybrids) of damselfish of the genera Amphiprion and Premnas
(Perciformes: Pomacentridae) and 10 species of host
sea anemones that display this phenomenon. The anemonefishes
live essentially unharmed among the tentacles of
the sea anemone, which are heavily armed with nematocysts;
this relationship is obligatory for the fish but not the
sea anemone. Numerous studies have been performed to
elucidate the mechanisms and the chemistry underlying
the protection of the anemonefish from stinging by the
nematocysts of the host sea anemone