Melanotaenia lacunosa
Mbuta Rainbowfish
Species Summary
Melanotaenia lacunosa 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.
Etymology
The species name lacunosa is Latin for full of lakes and ponds, referring to the many small ponds and larger lakes found in the Mbuta Basin, West Papua, Indonesia, where it is 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.
Distribution & Habitat
Melanotaenia lacunosa is known only from streams in the vicinity of Mbuta Lake and a swampy basin north of the lake itself near Etna Bay, West Papua Province. Lake Mbuta and the swampy basin are connected via streams and marshlands and effectively form a single body of water. The lake and swampy basin lie at 170 m elevation, and can be reached via a narrow valley only 3.5 km from the bay, or via a logging road from the coastal village of Avona in Kayumerah Bay. Depending on seasonal rainfall, the lake and basin can vary from completely flooded to marshland covered in tall grass and small ponds — this was the case when the type series was collected in 1997, though in subsequent visits in 2013 and 2023 it had become widely flooded. Drainage is subterranean, typical of this limestone region, with no surface outflow to Etna Bay.
Description & Comparison with Similar Species
Live males are bronze-yellow dorsally, shading to bluish white on the belly and yellowish posteriorly on the ventral body, with a dark blue mid-lateral stripe most conspicuous toward the rear of the body and a distinctive broad yellowish band immediately above it, narrower pale-yellow band below, and yellow-margined scales on the lower side. Melanotaenia lacunosa has the longest average snout length, preanal distance and prepelvic distance recorded for the group. Genetically it is the closest known relative of M. etnaensis, from which it differs sharply in gill-raker count despite the two being otherwise very similar.
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.