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).
- Length (excluding tail): 4.4 - 8.3 cm (2)