About Genicanthus lamarck (Lacepède, 1802)
Genicanthus lamarck (Lacepède, 1802) adults are pale greyish to whitish, marked with 4 to 5 irregular black undulating stripes. These stripes radiate out from the eye and run horizontally along the flanks. A wide black submarginal band is present on the dorsal fin, and the caudal fin is finely spotted. The topmost stripe is wider in females and juveniles. Males have a yellow patch on the crown, black pelvic fins, and very elongated lobes on the caudal fin; they also have white lobes on the caudal fin. Females have white pectoral fins and black caudal fin lobes. The dorsal fin contains 15 spines and 15 to 16 soft rays, while the anal fin has 3 spines and 16 to 17 soft rays. This species reaches a maximum total length of 25 centimetres (9.8 in). Genicanthus lamarck is distributed 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 Australian waters, it also occurs at Ashmore Reef and Cartier Island in the Timor Sea. Genicanthus lamarck lives at depths between 10 and 50 metres (33 and 164 ft). It inhabits areas of dense coral growth on the seaward slopes of reefs and on steep drop-offs. Its typical diet is zooplankton. It is normally observed over the seabed in small harems, consisting of one dominant male and 2 to 6 females. It is a sequential protogynous hermaphrodite: if the male in a harem disappears, the dominant female will change sex to become male.
