Chilatherina alleni
Allen’s Rainbowfish
Species Summary
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. Chilatherina 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 further 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). Chilatherina 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 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 midlateral 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 creeks near Siewa sometimes exhibit a spectacular pattern involving a bright red back and yellow fins.
Etymology
The genus name Chilatherina combines the Greek cheilos, lip, presumably referring to the several series of teeth projecting from the thick or swollen upper lip, and atherina, used here as a generic suffix for the family Atherinidae, in which rainbowfishes were classified at the time. The species is named in honour of Gerald R. Allen (b. 1942), of the Western Australian Museum, Perth, for his outstanding contribution to ichthyology and deep commitment to the study and conservation of the aquatic fauna of New Guinea.
Etymology compiled from C. Scharpf (2021), “Fishes of Sahul: An Etymological Survey (Part 4), the Rainbowfishes”, Fishes of Sahul 35(1): 1706–1714, and etyfish.org.
Distribution & Habitat
Chilatherina alleni were originally collected 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. Habitat consist of slow to moderately flowing tributary streams with gravel, rock, and sandy bottoms; water slightly turbid to clear or darkly stained with log snags and accumulated leaf litter. Water temperature 24–31°C, pH 6.0–8.4. This species was common throughout the Wapoga survey area from lowland creeks to mountain streams. Very abundant around Siewa in both small rainforest creeks and the much larger Tirawiwa River.
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.
Specimens originating from the type location near Siriwo Village were introduced into the European hobby in 2009.
References
- 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.