Apolemichthys trimaculatus is one of the 9 members belonging to the genus Apolemichthys, which together with 7 additional genera make up the family of angelfishes (Pomacanthidae) in which there are currently a total of 89 described species. It is a species that inhabits the outer walls of coral reefs at depths between 10 and 35 meters, in the waters of the Indian and Pacific Oceans (from the coasts of southern Africa to the east of Samoa, and from southern Japan and southern Australia).
The maximum total length of Apolemichthys trimaculatus is 26 cm, being its body oval-shaped and laterally compressed. Its dorsal profile is somewhat pointed, with a small mouth, and a complete lateral line that runs parallel to the contour of the body forming a large arc from the top of the operculum to the caudal peduncle. It has a continuous dorsal fin formed by a first region of 14 spines followed by a contiguous region of 16-18 soft rays. The anal fin has 3 spines and 17-19 soft rays.
The striking bright yellow color of the body will attract our attention, as it contrasts in the region of the mouth which is blue. Also notable on the body is the margin of the anal fin which forms a black triangular area, as well as a black circular spot on the front of the head, as well as another faint spot just behind the operculum. Juvenile specimens of Apolemichthys trimaculatus lack these spots, and instead have a thin horizontal black stripe across the eyes, as well as a series of vertical golden stripes on the sides of their bodies.
The diet of Apolemichthys trimaculatus is based on benthic invertebrates such as sponges and tunicates, and occasionally some crustaceans caught during the day. As a general rule, this species can be observed in pairs or small groups, being the juveniles more reserved and generally solitary.
The specimens of Apolemichthys trimaculatus are protandric hermaphrodites, that is, all specimens are initially females and throughout their lives can be converted to males. It is a rather territorial species in which a male will live in its territory with a small group of between 2 and 7 females.
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