Allen's rainbowfish (Chilatherina alleni)
|Size||Length (excluding tail): 4.4 - 8.3 cm (2)|
- Allen’s rainbowfish is known from just one river in West Papua, Indonesia.
- Allen’s rainbowfish was only described as a new species in 1997.
- Both male and female Allen’s rainbowfish have colourful patterning, although the male is slightly brighter than the female.
- Like other members of its genus, Allen’s rainbowfish is likely to use sticky threads to attach its eggs to vegetation.
Allen’s rainbowfish is classified as Vulnerable (VU) on the IUCN Red List (1).
Known from just one river in a remote province of northern Papua, Allen’s rainbowfish (Chilatherina alleni) is a small and attractive freshwater fish with a short, blunt snout and vibrant colouration. Both sexes have a brownish head and upper body, shading into turquoise towards the tail. A distinctive, horizontal dark blue stripe separates the colourful upper body from the underside, which is mainly dusky silver and marked with four to five black bars and a bright white stripe with orange margins towards the tail (2).
The male Allen’s rainbowfish has fins coloured with blues and reds, while the female lacks the red colouration and has bluish or transparent fins. The female is also slightly less brightly coloured overall than the male (2). As in other members of the genus, male Allen’s rainbowfish are typically larger and deeper-bodied than females, and the males also possess longer, somewhat pointed dorsal and anal fins, which in females are short and blunt (2) (3).
Allen's rainbowfish is found in the Aiborei River, part of the Siriwo drainage in West Papua, Indonesia (1) (2). The Siriwo River basin covers 4,765 square kilometres, but Allen’s rainbowfish is only likely to occupy a small part of this area (1).
Species in the genus Chilatherina are generally found in shallow pools in freshwater tributary streams. They typically prefer sections of the stream which have the maximum exposure to sunlight, as well as vegetation on which to lay their eggs, and a gravel or sandy substrate (3).
The river in which Allen’s rainbowfish is found is only up to one metre deep, while the pools this species prefers to inhabit are slightly shallower than this. The water in the river is cold and clear, and the substrate consists of gravel and rocks (2).
Very little is known about the biology of Allen’s rainbowfish. However, like other members of its family, Melanotaeniidae, this species is likely to form shoals and to feed on a variety of items including filamentous algae, small crustaceans, terrestrial insects and aquatic insect larvae (3) (4).
Members of the genus Chilatherina typically lay several eggs each day, attaching them with sticky, web-like threads to aquatic vegetation to prevent them from being displaced by the current. Hatching in these species may occur within 15 days, after which the young fish will grow quickly, reaching sexual maturity within a year (3).
At present, Allen’s rainbowfish is not considered to be threatened. However, due to its very restricted range and small population size this species is particularly vulnerable to potential future threats such as mining, road building, agriculture and water pollution (1).
There are currently no known conservation measures in place for Allen’s rainbowfish or its habitat (1). Further research into the biology of this species and the threats it faces are likely to be needed before any conservation action can be taken.
Find out more about Allen’s rainbowfish:
FishBase - Chilatherina alleni:
More information on conservation efforts in Indonesia:
Conservation International - Indonesia:
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- Algae: simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
- Anal fin: in fish, an unpaired fin on the under surface of a fish, behind the anus.
- Crustaceans: diverse group of animals with jointed limbs and a hard chitinous exoskeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
- Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans (whales, dolphins and porpoises).
- Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
- Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
IUCN Red List (April, 2012)
- Price, D.S. (1997) Chilatherina alleni, a new species of rainbowfish (Melanotaeniidae) from Irian Jaya. Revue Française d'Aquariologie, 24: 79-82.
- Allen, G.R. (1981) A revision of the rainbowfish genus Chilatherina (Melanotaeniidae). Records of the Western Australian Museum, 9(3): 279-299.
- Brown, C. (2002) Do female rainbowfish (Melanotaenia spp.) prefer to shoal with familiar individuals under predation pressure? Journal of Ethology, 20: 89-94.