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Chilatherina alleni [Siriwo] - photo© Gerald Allen |
Price, 1997
Allen's Rainbowfish
Species Summary
Chilatherina alleni have the upper half of the body brownish anteriorly becoming turquoise posteriorly, each horizontal scale row is separated by narrow brown or dull orange stripe. Mid-lateral band dark blue, occupying about two horizontal scales rows, from upper rear corner of eye to base of caudal fin, interrupted on its lower edge by about five, white indentations in area just behind pectoral fin. Lower half of body mainly dark silver, except for intense white stripe with lower margin of dull orange occupying scale row immediately below mid-lateral band. 4-5 diffused charcoal coloured bars on lower side between level of pelvic fin base and fin origin.
The first dorsal fin is light blue; second dorsal and anal fins translucent bluish becoming reddish on margins. Caudal fin translucent reddish. Pectoral and pelvic fins mainly translucent. Females slightly less intense with median fins mainly translucent to bluish without any red. Besides the colour differences noted above, males are typically deeper bodied than females. In addition, the second dorsal and anal fins short and blunt in females and somewhat elongated and pointed in males. There is a wide variation in colouration of this species depending on habitat. One variety has a reddish back, red fins and bright yellow stripe in the middle of the body. They exhibit an amazing range of colour variation; specimens from the rainforest creek near Siewa sometimes exhibit a spectacular pattern involving a bright red back and yellow fins. C. alleni may reach a maximum size of 10 cm, but are usually less than 7 cm. Males are usually much larger and deeper bodied than females.
Chilatherina alleni is most similar to Chilatherina fasciata of the northern New Guinea mainland and Chilatherina pricei of Yapen Island in Geelvink Bay. It differs greatly from these in colouration. C. alleni having a dark mid-lateral stripe and reddish fins in males. It further differs from C. fasciata in having a shorter blunter snout with the maxillary reaching to about the level of the anterior edge of the eye (falling well short in C. fasciata). It also differs from C. pricei in the modal counts of soft anal rays (usually 19-24 in C. alleni vs. 24-27 in C. pricei), and in the number of cheek scales (16-18 in C. alleni vs. 19-23 C. pricei).
Distribution & Habitat
Chilatherina alleni were originally collected near the village of Siriwo in 1994 from the Aiborei (Aboge) River, situated in the Derewo River Basin, southeast of Cenderawasih Bay in northern West Papua. They were again collected in 1998 during a Conservation International survey from tributaries of the Wapoga, Tirawiwa and Logari rivers. They have been collected in most river systems between Nabire and Wapoga. The species was common throughout the survey area from lowland creeks to mountain streams. Very abundant around Siewa in both small rainforest creeks and the much larger Tirawiwa River.
Habitats consist of slow to moderately flowing tributary streams where the substrate generally consists of gravel or sand, frequently littered with leaves or log debris; water slightly turbid to clear or darkly stained with log snags and accumulated leaf litter. Typically these fishes prefer sections of the stream which afford maximum exposure to sunlight. Water temperature 24-31°C and pH 6.0-8.4. Food items include small crustaceans, terrestrial insects such as ants and beetles, and various aquatic insect larvae.
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Chilatherina alleni [Wapoga] - photo© Gary Lange |
Remarks
Named alleni in honour of Gerald R. Allen, in recognition of his outstanding contribution to ichthyology and his deep commitment to the study and preservation of the aquatic fauna of New Guinea. Live specimens were collected from the type location near Siriwo Village and introduced into the hobby in 2008. Additional live specimens were collected for the aquarium hobby in 2012 from the Wapoga River.
Literature
Allen G.R. (1981) A Revision of the Rainbowfish Genus Chilatherina (Melanotaeniidae). Records of the Western Australian Museum 9(3): 279-299.
Price D.S. (1997) Chilatherina alleni, a new species of rainbowfish (Melanotaeniidae) from Irian Jaya. Revue française d'Aquariologie 24(3-4): 79-82.
Adrian R. Tappin
Updated May, 2016
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