Kapuasia falaris

Never heard of the genus Kapuasia? That’s what happened to me when a loach labelled as Kapuasia maculiceps was shown as newly imported on the website of Dutch wholesaler Ruinemans at the beginning of November 2024.

The genus Kapuasia was established in early 2024 by Kottelat and Tan for the taxon maculiceps, which was previously in Schistura and described as Nemacheilus. It is named after the Kapuas River basin in Borneo.
Kapuasia species differ from all other genera of the family Nemacheilidae in their mouth morphology – among other things, a strongly curved, U-shaped mouth and a thickened lower lip (Kottelat and Tan 2024). A glance at the genus description with illustrations of the genus, which was monotypic at the time, quickly showed that the imported animals could not be K. maculiceps. As the species name suggests, K. maculiceps has a spotted head, but the head of the newly imported animals is dark in colour with a light blaze.

At the beginning of December 2024, Kottelat, Tan and Hazan described a new Kapuasia species and it quickly became clear that the imported animals must be the newly described species, Kapuasia falaris. The species name ‘falaris’ then also refers to the conspicuous blaze – ‘phalaros’ and ‘ris’: with a white dot on the nose.

A polychromatic colouration of the caudal fin is striking in K. falaris – there are animals with red-coloured caudals as well as those without red colouration with more intensely coloured dark spots in all transitional forms. This is not a sexual difference; both males and females can have a strongly red-coloured caudal fin (see Fig. 2 Kottelat, Tan and Hasan 2024). Whether the colouration has a function in the social structure of the species will maybe be revealed over time by aquarists keeping this species.

The sexes can be distinguished by a suborbital flap under the eye, which only occurs in males. Females have a suborbital crease at this point.

No information is currently available about the habitat in the wild. The species occurs in the Barito River area in southern Kalimantan on Borneo. The coordinates given in the description refer to the center of the village (‘desa’) Pipitak Jaya, which is also  the type locality.

K. falaris appears to be an easy fish to keep in the aquarium. First experience shows that they can be kept in medium-hard water with a neutral to slightly alkaline pH value without any problems. The tank should be well covered in any case – the animals climb and jump well. The water should have a good oxygen saturation – a stronger current is very favourable for the animals but is not absolutely necessary. Artificial food such as tablets and granulated food are eaten just as readily as frozen (Artemia) and live food (Artemia naupli, Grindal). Their behaviour reminds me a little of the striped Pangio species, such as Pangio semicincta, which is also reminiscent of their coloration. If sufficient hiding places are provided, the animals are mainly seen when feeding. Apart from the occasional scuffle, they behave peacefully towards free-swimming fish and each other.

I would like to thank Heok Hui Tan (Lee Kong Chian Natural History Museum, National University of Singapore) for the permission to show images of K. maculiceps and the holotype of K. falaris here, Thomas Tillmann for organising the animals and Maurice Kottelat and Ralf Britz for the information on the author of the pictures – which I had for some reason overlooked in both papers…

Text and images unless stated otherwise: Achim Werckenthin

Literature:
Kottelat, M. & Tan, H.H. (2024)
Kapuasia, a genus name for ‘Nemacheilus’ maculiceps (Teleostei: Nemacheilidae).
The Raffles Bulletin of Zoology. 72. 105-109
DOI: 10.26107/RBZ-2024-0008

Kottelat, M., Tan, H.H. & Hasan, V. (2024)
Kapuasia falaris, a new species of nemacheilid loach from Borneo (Teleostei: Nemacheilidae).
The Raffles Bulletin of Zoology. 72. 479-487
DOI: 10.26107/RBZ-2024-0035