Melanotaenia garylangei (male) - photo© Gary Lange

Melanotaenia garylangei

Species Summary
Melanotaenia garylangei males have a blue colouration on the anterodorsal portion of the body and olive-green on the remainder of the upper side; side of body generally yellowish anteriorly; belly region red to orange; iris golden yellowish; mid-lateral blackish stripe covering two scale rows; narrow dark stripe above upper mid-lateral scale row regularly broken; red stripe above and 1-2 red stripes below the mid-lateral stripe; first dorsal light blue, second dorsal, pectoral, anal and middle portion of caudal fin red. A lateral row of 5-12 red scales behind the pectoral fin in the scale row below the dark midlateral stripe. Females with same stripe pattern, but generally light brown overall on body except whitish ventrally and without the blue nape and red fins.

Sexual maturity is reached at a size of approx. 25 mm SL and at around 6 months of age, based on aquarium observations. Males develop a deeper body than females, and have moderately elongated and pointed unpaired fins, compared with the short and rounded fins in females. Colour of the unpaired fins in males is red, fading to yellowish-orange towards the body; those of the females are translucent with a faint dark margin. In males, the tip of the first dorsal fin is coloured whitish-blue and extends posteriorly past the origin of the second dorsal fin, which is not the case with females. Depth of the body in adult males (over 50 mm SL) ranges from 32-37% of SL, and for females from 30-33% of SL. Males below 50 mm SL show the same proportions as females. Males develop elongated dorsal and anal fins from approx. 25 mm SL, based on aquarium observations.

Distribution & Habitat
Melanotaenia garylangei was found in several small rainforest streams crossing the road that was just recently built to the east and west of Dekai. The village of Dekai is located approximately 190 km inland from the southern coast of New Guinea on the Brazza River in the Eilanden River system. The water at the collection sites was clear and tannin-stained. Typical habitats were characterised by muddy substrate; submerged aquatic vegetation (Barclaya sp.) was present only at one site. Undisturbed habitats were partially covered by forest canopy, whereas disturbed sites were open to sunlight.

Fish species co-occurring with Melanotaenia garylangei include Melanotaenia goldiei, Melanotaenia rubrostriata, Pseudomugil sp., and Ambassis agrammus. All three Melanotaenia species recorded in this area occur in close proximity; in some cases all the species mentioned above were present in the same net haul. However, it appears that M. goldiei predominantly lives in faster flowing, open water, whereas M. rubrostriata is found closer to the stream edges. Melanotaenia garylangei apparently prefers shallow (10-20 cm depth) areas frequently covered with floating grass, as opposed to Pseudomugil sp., which was recorded predominantly in very shallow (5-10 cm depth) water.

Melanotaenia garylangei (pair) - photo© Gary Lange

Remarks
Melanotaenia garylangei is named in honour of Gary Lange, a well-known rainbowfish enthusiast in the USA who first discovered this species. Live specimens were collected by Gary Lange, Johannes Graf and Dan Dority in 2010, in the vicinity of Dekai Village. The species has been known to the aquarium hobby as Melanotaenia sp. "Dekai" or "Dekai Village"; it has also been known as the Golden Rainbowfish.

This species belongs to the "Maccullochi" group, a clade inhabiting southern New Guinea and parts of northern Australia. It is most similar to M. ogilbyi from the adjacent Unir River drainage, a species that shares most meristic and morphometric features and parts of the colour pattern. Melanotaenia garylangei is however clearly distinguished by having more rays in the second dorsal fin, and by conspicuous iridescent blue colouration of adult males along the upper lateral body between the head and first dorsal fin.

Literature
Graf J.A., F. Herder and R.K. Hadiaty (2015) A New Species of Rainbowfish (Melanotaeniidae), Melanotaenia garylangei, from Western New Guinea (Papua Province, Indonesia). Fishes of Sahul, 29 (2): 870-881.

Adrian R. Tappin
June, 2015