Genicanthus lamarck
A striped Indo-West Pacific angelfish with sex-changing social structure.
Genicanthus lamarck, also called the blackstriped angelfish or Lamarck's angelfish, is a marine angelfish in the family Pomacanthidae. Its range covers the Indo-West Pacific region.
Adults are pale greyish to whitish, with four or five irregular black wavy stripes that start near the eye and run horizontally along the body. A wide black band sits just below the edge of the dorsal fin, and the tail fin is covered in fine spots. Females and juveniles have a wider top stripe than males. Males show a yellow patch on the crown, black pelvic fins, and very long extensions on the tail fin. Their tail lobes are white, while females have white pectoral fins and black tail lobes. The dorsal fin has 15 spines and 15–16 soft rays; the anal fin has 3 spines and 16–17 soft rays. Maximum total length is 25 cm (9.8 in).
This species occurs from the Gulf of Thailand east through the Malayan Archipelago to the Solomon Islands, north to southern Japan, and south to the Great Barrier Reef. In Australia it also appears at Ashmore Reef and Cartier Island in the Timor Sea.
It lives at depths of 10 to 50 m (33–164 ft), in areas with dense coral on seaward reef slopes and steep drop-offs. Its diet consists mainly of zooplankton. Individuals are usually seen near the bottom in small harems—one dominant male with two to six females. They are sequential protogynous hermaphrodites: if the male disappears, the dominant female changes sex to become male.
The species was first formally described in 1860 as *Holocanthus caudovittatus* by French naturalist Bernard Germain de Lacépède, though no type locality was given. Its specific name honors French naturalist Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck. It is known to hybridize with the ornate angelfish (*Genicanthus bellus*).
*Genicanthus lamarck* is common in the aquarium trade and is also considered a food fish in the Moluccas.
Quick Facts
- Taxon
- Genicanthus lamarck
Facts from the source article.
Lore & Background
Genicanthus lamarck adults are pale greyish to whitish with 4-5 irregular black undulating stripes radiating from the eye and running horizontally along the flanks. The dorsal fin has a wide black submarginal band, and the caudal fin is finely spotted. Males have a yellow patch on the crown, black pelvic fins, and very elongated caudal fin lobes with white lobes, while females have white pectoral fins and black caudal fin lobes. The topmost stripe is wider in females and juveniles.
This species is found from the Gulf of Thailand east through the Malayan Archipelago to the Solomon Islands, north to southern Japan, and south to the Great Barrier Reef, including Ashmore Reef and Cartier Island in the Timor Sea. It inhabits areas of dense coral growth on seaward slopes and steep drop-offs at depths between 10 and 50 metres.
Genicanthus lamarck feeds on zooplankton and lives in small harems with a dominant male and 2-6 females. It is a sequential protogynous hermaphrodite: if the male disappears, the dominant female changes sex to become male. The species was first formally described in 1860 as Holocanthus caudovittatus by Bernard Germain de Lacépède, with no type locality given, and its specific name honors the French naturalist Jean-Baptiste Lamarck. It is known to hybridise with the ornate angelfish (Genicanthus bellus).
Reader's Guide
Genicanthus lamarck is frequently found in the aquarium trade, making it a notable species for marine aquarists. In the Moluccas, it is also regarded as a delicacy. Its significance lies in its distinctive appearance and its role as a sequential protogynous hermaphrodite, a reproductive strategy where females can transform into males when needed. This behavior, along with its harem-based social structure, provides insight into the adaptive biology of marine angelfish. The species' ability to hybridise with Genicanthus bellus further highlights its evolutionary relationships within the genus. Its wide distribution across the Indo-West Pacific, from the Gulf of Thailand to the Solomon Islands and southern Japan, underscores its ecological adaptability. The detailed description of sexual dimorphism—such as the yellow crown patch and elongated caudal fin lobes in males versus white pectoral fins in females—adds to its interest for both scientists and hobbyists. The species' presence in the aquarium trade and as a food source reflects its dual cultural and economic value.
Did You Know?
- Males have a yellow patch on the crown and black pelvic fins, while females have white pectoral fins.
- This species is a sequential protogynous hermaphrodite: if the dominant male disappears, the dominant female changes sex to become male.
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