About Melanotaenia duboulayi (Castelnau, 1878)
Male Melanotaenia duboulayi reach a maximum body length of 12 cm (4.7 inches), and are usually less than 10 cm (3.9 inches); females are typically smaller than males. This species has a slender, compressed body shape, and two dorsal fins positioned very close together, with the first dorsal fin being much smaller than the second. Fin colours range from clear to yellowish to red, with red flecks and dark margins; these dark margins become intensely black in males during spawning. Larger males can be distinguished from females by their brighter body colours, and by the elongation of the posterior rays in their second dorsal and anal fins. Females have smaller, rounded dorsal and anal fins that do not have dark edges. A prominent crimson red spot is present on the operculum. The body is generally silvery-blue or green, and can also range into deep bluish or yellow tones. Narrow yellow lines mark the species' scale rows, which are overlaid with colouring that goes from orange to brilliant red. Melanotaenia duboulayi shows considerable colour variation across its wide geographical range.
