Pomacanthus semicirculatus
A marine angelfish with distinct juvenile and adult color patterns.
Pomacanthus semicirculatus goes by several common names, including the semicircled angelfish, Koran angelfish, blue angelfish, zebra angelfish, and half-circled angelfish. This ray-finned marine angelfish belongs to the family Pomacanthidae and lives in the Indo-West Pacific Ocean. It sometimes appears in the aquarium trade.
Adults and juveniles of this species look very different from each other, a trait shared with other members of the genus *Pomacanthus*. Adult fish are brownish green, with blue edges on their scales that create a speckled blue pattern across the body and tail. All fins except the plain yellow pectoral fins have blue margins. The dorsal and anal fins have long, filamentous extensions. Juveniles, on the other hand, are blue-black with narrow white stripes running from top to bottom. The stripes are fairly straight near the head but become increasingly curved toward the tail base. Juveniles gradually take on adult coloration when they reach 8 to 16 centimeters (3.1 to 6.3 inches) in length. The dorsal fin has 13 spines and 20–23 soft rays, while the anal fin has 3 spines and 18–22 soft rays. This species can grow to a maximum total length of 40 centimeters (16 inches).
Its range spans the Indo-Pacific region, from the eastern coast of Africa—starting at the southern Red Sea coast of Sudan and extending south to South Africa—then east across the Indian and Pacific Oceans to Fiji, Tonga, and Samoa. It reaches as far north as southern Japan and south to Australia. Within Australian waters, it is widespread from the Houtman Abrolhos in Western Australia around the coast to as far south as Sydney on the eastern coast, with juveniles extending farther south to Merimbula. It also occurs at Christmas Island, the Cocos (Keeling) Islands, and Lord Howe Island in the Tasman Sea. Since 1999, it has been spotted sporadically off the east coast of Florida, and since 2005 at Oahu, Hawaii.
This fish lives at depths between 1 and 40 meters (3 feet 3 inches and 131 feet 3 inches) on sheltered coral reefs, feeding on algae, tunicates, and sponges. Juveniles are very timid and hard to approach, staying in shallow sheltered areas. Adults prefer coastal reefs with rich coral growth that offers plenty of hiding places. They are usually seen in pairs or alone, and adults have also been recorded from shipwrecks.
Quick Facts
- Taxon
- Pomacanthus semicirculatus
Facts from the source article.
Lore & Background
Adults of Pomacanthus semicirculatus are brownish green with scales edged in blue, creating a blue speckling over the body and tail. All fins except the plain yellow pectoral fins have blue margins, and the dorsal and anal fins bear long, filamentous growths. Juveniles are blue-black with narrow white stripes running from top to bottom; stripes are straight near the head and become increasingly curved toward the tail base. Juveniles gradually adopt adult coloration when they reach 8 to 16 centimeters in length.
The species was first formally described as Holacanthus semicirculatus in 1831 by French anatomist Georges Cuvier, with type localities including Timor, Bourou, Waigeo (Indonesia), and Port Praslin (New Ireland Island, Bismarck Archipelago, Papua New Guinea). The specific name semicirculatus means 'semicircular,' referring to the semicircular slender blue and white lines on the rear of juveniles, which are lost in adults. Some authorities place this species in the subgenus Arusetta.
Pomacanthus semicirculatus is found in the Indo-Pacific region from the eastern coast of Africa (southern Red Sea coast of Sudan to South Africa) east across the Indian and Pacific Oceans to Fiji, Tonga, and Samoa, north to southern Japan, and south to Australia. Within Australian waters it ranges from the Houtman Abrolhos of Western Australia to Sydney on the eastern coast, with juveniles extending to Merimbula. It also occurs at Christmas Island, Cocos (Keeling) Islands, and Lord Howe Island. It has been seen sporadically off the east coast of Florida since 1999 and at Oahu, Hawaii since 2005.
Reader's Guide
Pomacanthus semicirculatus is a marine angelfish of the family Pomacanthidae, found in the Indo-West Pacific Ocean. It is notable for the dramatic difference between juvenile and adult coloration, a trait common to the genus Pomacanthus. The species attains a maximum total length of 40 centimeters and inhabits sheltered coral reefs at depths between 1 and 40 meters. Juveniles are very timid and occur in shallow sheltered areas, while adults prefer coastal reefs with rich coral growth that provides hiding places; adults are typically encountered in pairs or as solitary individuals and have been recorded from wrecks. Its diet consists of algae, tunicates, and sponges. The species is frequently encountered in the aquarium trade, contributing to its recognition among marine hobbyists. Its sporadic appearances off Florida since 1999 and in Hawaii since 2005 indicate occasional range expansions or introductions beyond its native Indo-Pacific distribution.
Did You Know?
- The specific name semicirculatus means 'semicircular,' referring to the semicircular blue and white lines on juvenile fish.
- Adults have long, filamentous growths from the dorsal and anal fins.
- Juveniles gradually adopt adult coloration when they are 8 to 16 centimeters long.
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