Melanotaenia duboulayi
Description
Crimson Spotted Rainbowfish are a slender freshwater fish with a compressed body and two dorsal fins, the front dorsal fin being much smaller than the back. They reach a maximum size of 12cm however, they are much less than this at an average of below 10cm in length. Crimson spotted Rainbowfish display a wide variety of colours that changes according to the population's geographic location. Typically, they have a silver body tinged with blue, green or yellow, and orange-red scales marked with yellow lines. They also have a luminous rainbow colouring on their caudal fin. Crimson Spotted Rainbowfish are named for the conspicuous crimson-red spot that can be seen on their operculum (gill cover). Males can be separated by females as they tend to be larger and have a much brighter colouration. During the breeding season the dark margins of their fins become intensely black.
Spawning typically occurs between September to December when the water is between 24-29oC and just before the summer rains arrive. Crimson Spotted Rainbowfish will start spawning either at dusk or dawn just before it gets dark. The female will lay up to ten eggs (1-1.8mm in diameter) three to four times per day, which are fertilised by the male. Once fertilised, they stick to surrounding aquatic vegetation by long, thin threads. The eggs hatch 5 to 9 days after fertilisation and the hatchlings grow quickly reaching sexual maturity after less than 12 months.
This fish species can be found east of the Great Dividing Range from the Hastings River in New South Wales, to Baffle Creek south of Gladstone in Queensland. They prefer relatively still, clear water with a temperature between 10 to 34°C. The types of habitats they can be found in range from rivers, creeks, billabongs, swamps, and lagoons with thick aquatic vegetation. Within these habitats they can be seen in open water swimming in small schools, of up to 30 individuals, amongst the sub-surface plants, sunken timber and branches in deeper water.
Adaptations
- Schooling behaviour to reduce chances of predation
- Omnivorous feeding strategy and broad tolerance limits allow it to survive in a variety of habitats
Feeding relationships
- What I eat: Plant matter, aquatic insects, crustaceans, small tadpoles
- What eats me: Carnivorous fish, birds (e.g. Sacred Kingfisher), Crayfish, Turtles
Interesting facts
The Crimson Spotted Rainbowfish is the original "Australian Rainbowfish" and have been kept in hobby aquariums since the early 1900's. Between 1927 and 1930 they were introduced to international hobbyists, and were sent via steamship to Germany, then throughout Europe, and then to North America. They are most likely the species upon which the modern common name "Rainbowfish" is based.