Picture credit : Tim Long
Amphiprion Polymnus, also known as the Saddleback Clownfish or Yellowfin Anemonefish, is a black and white species of Anemonefish with a distinctive saddle. Like all Anemonefishes it forms a symbiotic mutualistic relationship with sea anemones and is unaffected by the stinging tentacles of the host anemone. It is a sequential hermaphrodite with a strict sized based dominance hierarchy. The female is largest, the breeding male is second largest, and the male non-breeders get progressively smaller as the hierarchy descends. They exhibit protandry, meaning the breeding male will change to female if the sole breeding female dies, with the largest non-breeder becomes the breeding male.
The Saddleback Clownfish do not migrate to other anemones to start new families, but stay in their host for their entire life time unless the anemone dies. This is also one of the few species that the adult pairs will allow several other adult pairs and sub adults to live within a very large anemone. In fact one diver reportedly counted 30 clownfish on one very large anemone.
If you would like to be able to identify fish on your dives, take a look at the PADI Fish Identification Specialty.