Melanotaenia etnaensis
Etna Bay Rainbowfish
Species Summary
Melanotaenia etnaensis belongs to the ‘Goldiei’ group of Melanotaenia, a closely related complex of rainbowfishes from southern and western New Guinea that has proven unusually prone to cryptic speciation. Members of the group share broadly similar body shape, meristics and colour pattern, and are most reliably distinguished from one another by genetic differences and their separate, non-overlapping (allopatric) distributions rather than by any single obvious external feature. At up to 100 mm SL it is the largest member of the group, well above the 62–90 mm SL typical of its Birds Neck relatives.
Distribution & Habitat
Melanotaenia etnaensis is confined to streams flowing into Etna Bay, on the southern coast of New Guinea about 100 km southeast of Kaimana, or its immediate vicinity. The bay is a spectacularly scenic, rainforest-fringed inlet extending some 55 km inland; the type locality, the Ambalanga River, lies near its mouth, with the species also found in small creeks in the bay’s inner reaches.
Description & Comparison with Similar Species
Live adult males are among the most colourful of the group, bluish grey dorsally with a large bluish patch above the pelvic fins, a yellowish patch with blue-black scale margins on the lower side, a strong blackish mid-lateral stripe, and yellowish-to-reddish dorsal and anal fins. Melanotaenia etnaensis has the shortest average caudal-peduncle length and the highest average number of anal rays recorded for the group; its closest genetic relative, M. lacunosa, is nonetheless readily told apart by an almost non-overlapping gill-raker count, one of very few morphological differences between any two ‘Goldiei’ group species that is essentially clean-cut.
Etymology
The species name etnaensis is a suffix denoting place, referring to the streams flowing into Etna Bay, West Papua, Indonesia, or its immediate vicinity, where it appears to be endemic.
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.
Account compiled for Home of the Rainbowfish from G. R. Allen, P. J. Unmack & R. K. Hadiaty (2016), “The Goldiei group of rainbowfishes from the Birds Neck Region with descriptions of five new species and recognition of Melanotaenia dumasi Weber”, aqua, International Journal of Ichthyology, 22(1): 1–32.
References
- Allen G.R., P.J. Unmack and R.K. Hadiaty (2016) The Goldiei group of rainbowfishes from the Birds Neck Region with descriptions of five new species and recognition of Melanotaenia dumasi Weber. aqua, International Journal of Ichthyology, 22(1): 1-32.