Saddleback Clownfish

A. polymnus is a small sized fish which grows up to 13 centimetres (5.1 in). In any anemonefish group, the female is always larger than the male, but in this species the male is almost equal in size to the female. Its body has a stock appearance, oval shape, compressed laterally and with a round profile. The body color ranges from dark brown to yellow orange and this species has two or three white bars. The white head bar is thick and located just behind the eyes. A large white abbreviated saddle shape or slanted white bar across the middle of the fish's body makes it quite obvious to see how it got the name Saddleback. In some varieties, typically those specimens initially associated with Heteractis crispa anemone, the saddle shape may extend up onto the fish's Dorsal fin with a third white bar or margin located across the caudal peduncle, (pictured in taxobox).

A. polymnus is found in the center of the Indo-Pacific area, known as the Coral Triangle, from the Philippines to Indonesia and New Guinea.It is also found in northern Australia, Melanesia and to the Ryukyu Islands of southern Japan. Adults inhabit silty lagoons and harbour areas in depth range from 2 to 30 metres (6.6 to 98.4 ft).

Like all anemonefish, A. polymnus is omnivorous and its diet is based on zooplankton, small benthic crustaceans and algae.

The relationship between anemonefish and their host sea anemones is not random and instead is highly nested in structure. A. polymnus is a specialist, being hosted by 2 out of the 10 host anemones:

Stichodactyla haddoni (Saddle carpet anemone)

Anemonefish and their host anemones are found on coral reefs and face similar environmental issues. Like corals, anemones contain intracellular endosymbionts, zooxanthellae, and can suffer from bleaching due to triggers such as increased water temperature or acidification. The other threat to anemonefish is collection for the marine aquarium trade where anemonefish make up 43% of the global marine ornamental trade, and 25% of the global trade comes from fish bred in captivity, while the majority are captured from the wild, accounting for decreased densities in exploited areas. While bleaching is a significant threat to anemonefish and their host anemones, there is evidence suggesting that collection compounds the localised impact of bleaching. This species was not evaluated in the 2012 release of the IUCN Red List.