Chilatherina pagwiensis
Pagwi Rainbowfish
Species Summary
Chilatherina pagwiensis is a slender rainbowfish described in 2012 from a single creek system near Pagwi village in the Sepik River drainage of Papua New Guinea. It was first collected in 1982 but misidentified at the time as C. fasciata, a similar species with which it shares its home creek; its distinct status only came to light after further collections in 2007 and genetic comparison with its relatives. Genetically it proves closest to the common ancestor of C. axelrodi and C. campsi, while morphologically its nearest look-alike is C. campsi, a species of hilly and mountainous streams across northern Papua New Guinea.
Etymology
The species name pagwiensis is a suffix denoting place: it is known only from a single creek near Pagwi village, Sepik River system, Papua 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 pagwiensis is known only from Kuins (or Huins — accounts differ on the correct spelling) Creek, a tributary of the Sepik River crossed twice by the Maprik–Pagwi road, once in its upper reaches and once lower down. As it appears to be widespread within this creek, it seems likely to occur in similar habitats elsewhere in the wider Sepik drainage, though it has not yet been recorded there. The type locality is a quiet pool in a small creek flowing through secondary forest; the type series was also taken from a slow-flowing, closed-canopy forest stream over rock and mud to about 1.8 m deep, roughly 400 km upstream from the sea at only about 30 m elevation. It occurs alongside C. fasciata in the same creek.
Description
A slender rainbowfish reaching at least 76 mm SL, both sexes noticeably less deep-bodied than most other rainbowfishes. Freshly collected fish are pale grey on the upper back grading to white over most of the body, with a diffuse greyish stripe along each scale row of the back; the fins are generally reddish, except for the semi-translucent whitish pectoral fins. Preserved specimens show a diffuse blackish mid-lateral stripe from the gill cover to the tail base, with 6–7 intense black spots along its lower edge and two short dark bars on the lower side above the front of the anal fin. Like its closest relatives, it lacks vomerine and palatine teeth altogether.
Comparison with Similar Species
Chilatherina pagwiensis and C. campsi share slender bodies and toothless vomer and palatine bones, but differ consistently in fin-ray counts: Chilatherina pagwiensis usually has 10–12 soft dorsal rays and 20–21 soft anal rays, compared to 13–15 and 21–26 (mostly 22–23) respectively in C. campsi. It is even more easily confused with its creek-mate C. fasciata, especially in fish under about 60 mm SL, but that species can always be told apart by the presence of both vomerine and palatine teeth, by its somewhat higher fin-ray counts, and by growing distinctly larger (to 105 mm SL versus under 80 mm SL). Although genetically Chilatherina pagwiensis is closest of all to C. axelrodi, that species is readily separated on sight: it has both vomerine and palatine teeth, a much deeper body in mature males, and a strikingly different colour pattern of a broad, broken black mid-lateral stripe with 6–10 black bars on the lower sides.
Remarks
Chilatherina pagwiensis is not currently available in the aquarium hobby.
Account compiled for Home of the Rainbowfish from G. R. Allen & P. J. Unmack (2012), “A new species of Rainbowfish (Chilatherina: Melanotaeniidae), from the Sepik River System of Papua New Guinea”, aqua, International Journal of Ichthyology, 18(4): 227–237.
References
- Allen G.R. & P.J. Unmack (2012) A new species of Rainbowfish (Chilatherina: Melanotaeniidae), from the Sepik River System of Papua New Guinea. Aqua, International Journal of Ichthyology 18(4): 227-237.