Amphiprion pacificus
A rare, endemic anemonefish of the western Pacific.
Amphiprion pacificus is a type of anemonefish that lives in the western Pacific Ocean. Like all anemonefish, it has a mutually beneficial relationship with sea anemones and is not harmed by their stinging tentacles. This species is a sequential hermaphrodite with a strict hierarchy based on size: the largest individual is the female, the next largest is the breeding male, and the remaining non-breeding males get smaller as the rank goes down. It shows protandry, meaning that if the only breeding female dies, the breeding male will change into a female, and the largest non-breeder will become the new breeding male. Its natural diet consists of zooplankton.
The body of *A. pacificus* is pinkish brown to dark brown, usually fading to yellowish or orange on the lower body and abdomen. It belongs to the skunk complex and has a white stripe running along the top of the back, from the middle of the snout to the base of the tail fin. The fins are whitish or semi-translucent. It has 9 dorsal spines, 2 anal spines, 18 to 20 dorsal soft rays, and 12 to 13 anal soft rays. The four specimens originally used to describe the species measured between 3.09 and 4.83 cm (about 1¼ to 2 inches).
Unlike some other anemonefish, *A. pacificus* does not show color variations based on location, sex, or host anemone. It looks almost identical to *Amphiprion akallopisos*, but the two are separated by a wide geographic range, making location the easiest way to tell them apart. Despite their similar appearance, genetic studies show that *A. pacificus* is clearly different from *A. akallopisos* and is more closely related to *Amphiprion sandaracinos*, which has a uniform color and a white stripe that extends onto the upper lip. Three other anemonefish species—*A. barberi*, *A. chrysopterus*, and *A. clarkii*—live in the same area, but they are easy to distinguish because they lack the white stripe along the back.
*A. pacificus* is found in the western Pacific around Wallis Island, Tonga, Fiji, and the Samoan Islands, a region known for high numbers of unique species. It is not common within its range and is usually found at depths of 4 to 10 meters (13 to 33 feet). The relationship between anemonefish and their host anemones is highly structured, and *A.
Quick Facts
- Taxon
- Amphiprion pacificus
Facts from the source article.
Lore & Background
The body of A. pacificus is pinkish brown to dark brown, usually grading to yellowish or orange on the lower side including the abdomen. It is a member of the skunk complex, with a characteristic white stripe along the dorsal ridge line from the midline of the snout through to the base of the caudal fin. The fins are whitish to semi-translucent. It has 9 dorsal spines, 2 anal spines, 18-20 dorsal soft rays, and 12-13 anal soft rays. The four specimens that were the basis of the description ranged from 3.09 to 4.83 cm.
Like all anemonefishes, it is a sequential hermaphrodite with a strict size-based dominance hierarchy: the female is largest, the breeding male is second largest, and the male non-breeders get progressively smaller. It exhibits protandry, meaning the breeding male will change to female if the sole breeding female dies, with the largest non-breeder becoming the breeding male. Its natural diet includes zooplankton. Unlike some other anemonefish, A. pacificus does not show color variations based on geographic location, sex, or host anemone.
A. pacificus is found in the western Pacific at Wallis Island, Tonga, Fiji, and Samoan Islands, a regional hotspot of endemism. It is not common within its range and is generally found at depths of 4 to 10 metres. It is highly specialised, being hosted by only one out of the six host anemones found in the region: Heteractis magnifica.
Reader's Guide
Amphiprion pacificus is of particular conservation concern due to several characteristics that elevate extinction risk: a small geographic range, small local population, and extreme habitat specialisation. It is an endemic species with only one host anemone, Heteractis magnifica, and is not common within its limited range. Anemonefish and their host anemones face similar environmental issues as coral reefs, including bleaching due to increased water temperature or acidification, as anemones contain intracellular endosymbionts called zooxanthellae. Despite these concerns, this species was not evaluated in the 2012 release of the IUCN Red List. Its significance also lies in its taxonomic relationships: although almost identical in appearance to A. akallopisos, genetic results indicate A. pacificus is well differentiated from that species and is more closely related to A. sandaracinos. Three other anemonefish species are found within its range—A. barberi, A. chrysopterus, and A. clarkii—but these are easily distinguished by the absence of the white stripe on the dorsal ridge.
Did You Know?
- A. pacificus is hosted by only one species of sea anemone: Heteractis magnifica.
- It exhibits protandry: the breeding male changes to female if the sole breeding female dies.
- The four specimens used for its description ranged from 3.09 to 4.83 cm in length.
- It is found only at Wallis Island, Tonga, Fiji, and Samoan Islands in the western Pacific.
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