Gastromyzon is a genus of fishes found exclusively on the island of Borneo. Species
in this genus, known as torrent loaches, are obligate bottom-dwellers and exhibit
extreme morphological adaptations for life in torrential waters. They have a
streamlined shape, wide head, and tapering body. These fish are poor swimmers
and have lost the ability to hover or swim in mid-water. As a consequence, fishes
in this genus have evolved new modes of locomotion, which involve creeping
and crawling along the bottom and around submerged rocks. In most species,
the ventral side of the fish is flat, made up of fused disks. Torrent loaches orient
themselves facing upstream, clinging to rocks to avoid being swept downstream
with the moving water. Additionally, individuals tend to show coloration patterns
that allow them to blend in with their environment.
Torrent loaches generally inhabit small, clear, fast moving waters with a rocky
substrate. They range in size from 5 to 10 cm. Their diet consists mainly of algae,
which they scrape off the rocks to which they cling.
(Inger and Kong 1961; Tan and Leh 2006; Tan and Sulaiman 2006)