Clownfish

Clownfish are unique in that they live in complete symbiosis with sea anemones. The fish hide among the tentacles of anemones to protect themselves. In exchange for this, they rid the anemones of small parasites and bring them food. Clownfish are hermaphrodite. The largest specimen is always female. If the female dies, the second largest male then becomes a female and the third largest becomes the breeding male. Clownfish are united for life.