Melanotaenia aruensis
Aru Rainbowfish
Species Summary
The Aru Archipelago, a cluster of islands on the shallow continental shelf between New Guinea and northern Australia, was largely overlooked by ichthyologists for a century after Dutch collectors first sampled its rivers in 1907–09. Aquarium enthusiast Heiko Bleher brought Aru rainbowfishes to hobbyist attention after visits in 2004 and 2007, and two expeditions in 2013 (organised by Gerald Allen, Mark Erdmann and colleagues, with genetic work by Peter Unmack) revealed the islands to be an unexpected hotspot of rainbowfish speciation: seven species in all, most found nowhere else. Despite its superficial resemblance to the other ‘Australis’ group species found on the Aru Islands, genetic data place Melanotaenia aruensis closer to species from northern Australia.
Etymology
The species name aruensis is a suffix denoting place, referring simply to the Aru Islands, Maluku Province, Indonesia, the type locality.
Etymology compiled from C. Scharpf (2022), “Fishes of Sahul: An Etymological Survey (Part 5), the rainbowfishes (continued)”, Fishes of Sahul 36(4): 1968–1992, and etyfish.org.
Distribution & Habitat
Melanotaenia aruensis is known from two locations 34 km apart — the type locality on Trangan Island and a small river in southern Kobroor Island — separated today by saltwater barriers. The Trangan site lies downstream of a spectacular 75 m limestone tunnel, in clear, slow-flowing water 10–12 m wide over a rocky limestone bottom with abundant fallen timber for cover; the species was common at both sites.
Description & Comparison with Similar Species
Live males are grey-brown on the head and forebody, with the rear two-thirds of the upper body bluish grey and each scale finely edged in bronze; the second dorsal fin carries a relatively broad whitish margin. Its in situ colour pattern closely resembles that of M. patoti — both share a large brownish zone over the head and forebody giving way to orange or bronze stripes behind — and the two are best separated by a more slender caudal peduncle, a longer maxilla, more cheek scales and a larger eye in Melanotaenia aruensis. Genetically, however, Melanotaenia aruensis is only distantly related to its geographic neighbour M. albimarginata, from which it is hard to tell apart except by a slightly larger eye.
Account compiled for Home of the Rainbowfish from G. R. Allen, R. K. Hadiaty, P. J. Unmack & M. V. Erdmann (2015), “Rainbowfishes of the Aru Islands, Indonesia with descriptions of five new species and redescription of M. patoti Weber and M. senckenbergianus Weber”, aqua, International Journal of Ichthyology, 21(2): 71–106.
References
- Allen G.R., R.K. Hadiaty, P.J. Unmack and M.V. Erdmann (2015) Rainbowfishes (Melanotaenia: Melanotaeniidae) of the Aru Islands, Indonesia with descriptions of five new species and redescription of M. patoti Weber and M. senckenbergianus Weber. aqua, International Journal of Ichthyology 21(2): 66-108.