Melanotaenia mamahensis
Mamah Rainbowfish
Species Summary
Melanotaenia mamahensis 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. It is the westernmost known member of the northern branch of the group, occurring just east of the mouth of the Omba–Woromi corridor, a low (to 160 m elevation) pass linking southern and northern New Guinea drainages across the narrow, 65 km-wide isthmus between Etna Bay and Cenderawasih Bay. The corridor is thought to explain how ‘Goldiei’ group ancestors, otherwise a southern New Guinea lineage, came to colonise the northern drainages that are now home to M. bowmani, M. grunwaldi and Melanotaenia mamahensis.
Etymology
The species name mamahensis is a suffix denoting place, referring to Sungai Mamah, West Papua Province, Indonesia, its only known area of occurrence.
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 mamahensis is known only from the type locality, Sungai Mamah, a clear, slow-flowing rainforest creek about 50 km west of Nabire near the edge of Cenderawasih Bay, where it was reported as abundant and swimming in large groups, especially in deeper, shaded sections.
Description & Comparison with Similar Species
Live adult males are brown to bluish grey dorsally, whitish to pale bluish grey below, with a blue mid-lateral stripe and a relatively broad yellow zone running immediately above and parallel to it; the first dorsal fin is reddish anteriorly grading to bluish posteriorly, and the anal fin is red basally. Melanotaenia mamahensis has the shortest average snout length, predorsal distance and number of prepelvic scales recorded for the group.
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.