Adult male Melanotaenia dumasi are greyish, frequently with a coppery sheen on back, grading to whitish anteroventrally and blue posteroventrally; narrow orange stripe between horizontal scale rows on upper side; dark blue to blackish mid-lateral stripe from eye to caudal-fin base, widest portion on caudal peduncle, covering two horizontal scale rows; red-orange stripe immediately above and below dark mid-lateral stripe; upper portion of head blue brownish, lower half bluish white with silvery stripe behind eye extending across upper cheek and middle of operculum, usually punctuated posteriorly with small reddish spot; dorsal, anal, caudal fins translucent reddish; pelvic fins white; pectoral fins translucent. Colour pattern of female similar to that of male except less vivid and fins are mainly translucent, lacking reddish hue.
Melanotaenia dumasi is a member of the "Goldiei" rainbowfish group that share a wide range of morphological and meristic features and lack notable differences, as would be expected for closely related species. Due to their great similarity, the species belonging to the "Goldiei" group are most reliably distinguished on the basis of genetic differences, colouration, and their geographically isolated distribution. The challenge with the "Goldiei" species group is that while they all have strong genetic differences and some clear colouration differences, morphological and meristic differences are minimal in most cases.
Distribution & Habitat
Melanotaenia dumasi is currently known only from the Omba (Urama on some maps) river system of West Papua, including streams in the vicinity of Lake Yamur where it is common in small creeks flowing into the main lake. Temperature and pH values recorded by Gerry Allen during July 1999 ranged from 24.4-26.0°C and 7.4-7.9 respectively.
The holotype of M. dumasi was collected in August 1903 by the Netherlands New Guinea Expedition under the supervision of the German geologist Arthur Wichmann. The type locality is the Wa Udu River, which is the main outflow from Lake Yamur, connecting it with the Omba River (formerly called the Urama), which lies about 7 km downstream. The Omba then follows a meandering, 165 km path to the Arafura Sea. The mouth is situated about 16 km southeast of Etna Bay. Three paratypes were obtained in 1909 during a reconnaissance of the Urama Basin led by Captain K.F. Koch, the Dutch military commander of the Western Detachment in New Guinea. These were collected from the Wagani River, a tributary of the upper Urama River.
Allen G.R., P.J. Unmack and R.K. Hadiaty (2016) The Goldiei group of rainbowfishes (Melanotaeniidae) from the Birds Neck Region of New Guinea (Papua and West Papua Provinces, Indonesia) with descriptions of five new species and recognition of Melanotaenia dumasi Weber. aqua, International Journal of Ichthyology 22(1): 1-32.
Adrian R. Tappin