Taxonomy & naming
Gastromyzon ctenocephalus was described by Roberts in 1982, with a type locality at Senah in Sarawak, Malaysian Borneo. The Catalog of Fishes (Eschmeyer, CAS) is the authority for the valid name. Gastromyzon is the type genus of Gastromyzontidae. Later revisions of Bornean species, notably Tan (2006), reorganised the genus.
Morphology
Gastromyzon species are broad and flat, with the pectoral and pelvic fins expanded into a sucker disc that holds the fish against rock in strong current. FishBase gives a maximum of 2 in SL. The epithet ctenocephalus is generally read as comb head, from the Greek ktenos and kephale.
Habitat
Gastromyzon of this kind live in clear, fast, well-oxygenated hill streams over cobble and boulder. FishBase lists the species as freshwater and demersal, from western Borneo, at 19 to 23 C. The type locality is Senah in Sarawak, northern Borneo.
Feeding
Gastromyzon graze biofilm and small invertebrates from rock surfaces. No dietary study of this species has been published.
Mating
Courtship has not been described for this species.
Breeding
Spawning has not been described, in the wild or in captivity.
In the aquarium
As with other Gastromyzon, success depends on cool, highly oxygenated, fast-moving water, a mature rockscape with growing biofilm, and several fish kept together. FishBase gives 19 to 23 C, which is a useful ceiling; warm, still or newly set up tanks are the usual cause of losses. A pH range has not been published for this species.
Conservation
The IUCN lists Gastromyzon ctenocephalus as Near Threatened, meaning it is close to qualifying for a threatened category. Its known range is small, in western Borneo, so wild-collected animals in the trade should be viewed with that in mind.