Of the over 1,000 anemone species that live in the ocean, only 10 species coexists with the 26 species of tropical clownfish. Within these species, only select pairs of anemone and clownfish are compatible. Together, they are obligatory symbionts, which means that each species is highly dependent on the other for survival. Symbiosis between the two species is achieved in a variety of ways including a mutual protection from predators, an exchange of nutrients, and the clownfish’s tolerance of anemone nematocysts.