Melanotaenia utcheensis
Utchee Creek Rainbowfish
Species Summary
Melanotaenia utcheensis has an overall body colouration of silvery-white, often with a faded orange colour near the midline. The head and gill region is silver to pink and fish often have a reddish cheek patch. Scales have a bluish iridescence, especially on the upper half of the body. There is an orange stripe between each horizontal scale row. The mid-lateral band starts dark at the tail and fades forwards, tending towards blue in males and black in females. Anal, dorsal, pelvic and caudal fins range from translucent to deep red, being most strongly coloured in males. The anal, second dorsal and pelvic fins often have black margins, especially in males. Pectoral fins are translucent. Males tend to be more brightly coloured than females. Males are also deeper bodied and have longer pelvic, dorsal and anal fins.
Genetic studies beginning in the mid 1990’s revealed the existence of significant genetic variation between populations of M. splendida that occur in the upland streams of north Queensland. In particular, these studies highlighted the degree of isolation of upland populations from the lowland populations. Subsequent genetic research suggested that at least some of these species were unusual variants of M. splendida - or populations displaying genes that have traits of more than one species. As a direct result of some of this research, M. utcheensis was described as a new species in 2001.
Melanotaenia utcheensis is morphologically distinct from the broadly sympatric M. eachamensis and M. splendida. In particular, M. utcheensis has more first dorsal spines and fewer vertical scale rows and anal rays than M. splendida, and fewer soft second dorsal rays and more pectoral rays than M. eachamensis. Melanotaenia utcheensis is also generally smaller than either M. splendida or M. eachamensis and intermediate between them in eye diameter, predorsal length, head depth and body depth.
Etymology
The species name utcheensis is a suffix denoting place, referring to Utchee Creek, Queensland, the type locality; the name also recognises its being sold in the aquarium trade as the “Utchee Creek Type.”
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 utcheensis have been collected from the Utchee, Fisher, Rankin and Short creeks, plus an unnamed creek, in the North and South Johnstone River catchments in north Queensland. They have been found in sites with moderate to high water flow over cobbles and boulders. The Johnstone River flows into the Coral Sea near the north Queensland town of Innisfail. The river branches about 5 km from the mouth into the North and South Johnstone Rivers, both of which have their sources on the Atherton Tablelands.
Rankin and Fisher Creeks flow northeast into the lower North Johnstone River. Short Creek and an unnamed creek are in the upper North Johnstone a little bit upstream of Gillies and Dirran Creek and they enter from the opposite side of the river. Utchee Creek feeds into the South Johnstone River on the coastal plain upstream of Innisfail. Melanotaenia utcheensis may also occur in Ithica River and Gillies, Williams and Tregothanana Creeks. Melanotaenia utcheensis also co-occurs with the more common M. eachamensis in Bromfield Swamp.
Biology & Ecology
Not a lot is known about the biology or ecology of M. utcheensis in their natural environment. Most information is mainly based on aquarium observations. Under aquarium conditions, pre-spawning behaviour usually occurs in the morning and may continue for up to an hour before spawning takes place. During this period the colours in both sexes become more intense, but to a lesser extent in the female.
The eggs hatch after an incubation period of four to nine days depending on temperature. Temperature is one of the major factors that influences the embryonic period for rainbowfishes. Average embryonic period is about 5–6 days at 28°C (+/- 2°C). The average larval length of M. utcheensis at hatching ranges from 2 to 4 mm, which is similar to other rainbowfish species.
Remarks
Studies have shown that there has been some degree of hybridisation between M. splendida and M. utcheensis. Genetic analyses suggest that M. utcheensis is an old species that evolved in isolation and that M. splendida has colonised the region in more recent times, possibly as a result of changes in river catchments. There are also some small variations in colour and morphology between the North and South Johnstone River populations. These populations may undergo species separation after further genetic studies. (P. J. Unmack 2009, pers. comm.)
The distribution of Melanotaenia species as determined from the distribution of mtDNA lineages is shown in the map below.
1: Tinaroo Dam (M. splendida) 2: Lake Euramoo (M. eachamensis); 3: Upper North Johnstone R. (M. splendida); 4: Ithica River (M. utcheensis); 5: Short Creek (M. utcheensis); 6: unnamed tributary (M. utcheensis); 7: Gillies Creek (M. utcheensis); 8: Dirran Creek (M. eachamensis); 9: Upper South Johnstone River (M. eachamensis); 10: Rankin Creek (M. utcheensis); 11: Fisher Creek (M. utcheensis); 12: Lower South Johnstone River (M. splendida); 13: Utchee Creek (M. utcheensis); 14: Tregothanana Creek (M. utcheensis). ~ McGuigan, 2001.
References
- Flint N. (2005) Sublethal effects of diel fluctuations in dissolved oxygen saturation on freshwater fishes from tropical Queensland. PhD thesis, James Cook University.
- McGuigan K.L., D. Zhu, G.R. Allen and C. Moritz (2000) Phylogenetic relationships and historical biogeography of melanotaeniid fishes in Australia and New Guinea. Marine and Freshwater Research 51: 713-723.
- McGuigan K.L. (2001) An addition to the rainbowfish (Melanotaeniidae) fauna of north Queensland. Memoirs of the Queensland Museum 46: 647-655.
- Martin K.C. & S. Barclay (2017) Factors influencing distribution and form of the Utchee Rainbowfish Melanotaenia utcheensis (Melanotaeniidae). Fishes of Sahul 31(2): 1095-1117.
- Pusey B., M. Kennard and A. Arthington (2004) Freshwater Fishes of North-Eastern Australia. CSIRO Publishing.