Threespot Humbug, Dascyllus trimaculatus (Rüppell 1829)

Other Names: Threespot Damsels, Threespot Dascyllus, Three-spot Dascyllus, Three-spot Humbug

A Threespot Humbug, Dascyllus trimaculatus, at North Solitary Island, New South Wales. Source: Ian V. Shaw / Reef Life Survey. License: CC BY Attribution

Summary:

A black to greyish humbug with a white blotch or spot on the upper side. Juveniles are black often with bluish scale centres, and have a white blotch on the forehead and another on the upper side. Adults lack the spot on the head, and the spot on the sides becomes smaller and disappears with age. Some individuals also have yellow caudal, anal and pelvic fins.

Cite this page as:

Bray, D.J. 2025, Dascyllus trimaculatus in Fishes of Australia, accessed 30 Apr 2025, https://fishesofaustralia.net.au/home/species/349

Threespot Humbug, Dascyllus trimaculatus (Rüppell 1829)

More Info

Distribution	South of Perth, Western Australia, to offshore reefs in the north, and Ashmore Reef in the Timor Sea, to New Year Island, Northern Territory, and the far northern Great Barrier Reef, Queensland, and reefs in the Coral Sea, to central New South Wales, with juveniles south to at least Narooma; also Cocos (Keeling) Islands and Christmas Island in the eastern Indian Ocean, and the Lord Howe Province (and possibly Norfolk Island) in the Tasman Sea. Elsewhere the species occurs in the tropical, Indo-west-central Pacific: Red Sea and East Africa, east north to the Austral Islands (French Polynesia), north to the Philippines, Taiwan, southern Korea and southern Japan, south to Australia and New Caledonia. Inhabits mangrove lagoons, coral and rocky reefs, usually near branching corals. Groups of adults usually frequent coral heads and large rocks, while juveniles often shelter among the spines of Diadema sea urchins, large sea anemones or in branching corals.
Features	Dorsal fin XI, I,14-16; Anal fin II,14-15. Body depth 1.4-1.6 in SL. Margins of preorbital, suborbital and preoperculum finely serrated.
Biology	Species of the genus Dascyllus are obligate coral dwellers. Until recently, it was presumed that all species of Dascyllus were protogynous hermaphrodites (ability to change sex from female to male). However, research has shown that Dascyllus trimaculatus is a gonochrist (does not undergo sex change), and that the protogynous pattern of gonadal development in D. trimaculatus is non-functional (Asoh & Kasuya 2006).
Etymology	The specific name trimaculatus is from the Latin tres (= three) and macula (= spot), in reference to the three white spots on the body of this species (juveniles).
Species Citation	Pomacentrus trimaculatus Rüppell, 1829, Fische des Rothen Meeres. 2: 39. Type locality: Massawa, Eritrea, Red Sea.
Author	Bray, D.J. 2025
Resources	Atlas of Living Australia Australian Faunal Directory Catalog of Fishes

Threespot Humbug, Dascyllus trimaculatus (Rüppell 1829)

References

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