The Squretail Rabbitfish (Siganus luridus) has a compressed body, with a depth 2.1 to 2.8 times its standard length. It typically reaches 20 cm (7.9 in) in total length, with a maximum recorded size of 30 cm (12 in). The caudal fin is truncate, giving it its common name. The dorsal fin has 13-14 spines and 10 soft rays, while the anal fin contains 7 spines and 9 soft rays. A single row of incisor-like teeth is present in its jaws, each tooth having 1 or 2 lateral cusps. Colouration varies from olive green to dark brown, often with a mottled pattern. Pectoral fins are hyaline-yellow; the caudal fin features dark bars. Venomous spines are present in its dorsal, anal, and pelvic fins. Its scientific name luridus refers to a pale yellowish colour noted by the collector Christian Gottfried Ehrenberg; however, describer Eduard Rüppell depicted it as bluish black with paler spots and a yellowish ring around the pupil.
This species inhabits hard substrates such as coral and rocky reefs, at depths between 2 and 40 m (6 ft 7 in and 131 ft 3 in). Adults are herbivores, active during the day and seeking shelter in cavities at night. Often encountered in schools, but also singly, it grazes on algae, including larger brown algae species and other macrophytes. When threatened, it suddenly stops and erects its dorsal, anal, and pelvic fins to display its venomous spines.
Spawning occurs between April and August when seawater temperatures range from 24 to 29 °C (75 to 84 °F). Eggs and larvae are planktonic, feeding on phytoplankton and zooplankton. This species is hermaphroditic, capable of changing sex from male to female. It is territorial, lays its eggs in the water, and reaches sexual maturity in one year, growing quickly.
- mottled olive green to dark brown body
- hyaline-yellow pectoral fins
- truncate caudal fin with dark bars
Why it's threatened
Major threats to Siganus luridus in the Persian Gulf are unknown.
Threat classification from the IUCN Red List.
